text: // SPDX-License-Identifier: GPL-2.0
  #include <linux/ceph/ceph_debug.h>
  
  #include <linux/backing-dev.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/pagemap.h>
  #include <linux/writeback.h>	/* generic_writepages */
  #include <linux/slab.h>
  #include <linux/pagevec.h>
  #include <linux/task_io_accounting_ops.h>
  #include <linux/signal.h>
  #include <linux/iversion.h>
  #include <linux/ktime.h>
  
  #include "super.h"
  #include "mds_client.h"
  #include "cache.h"
  #include "metric.h"
  #include <linux/ceph/osd_client.h>
  #include <linux/ceph/striper.h>
  
  /*
   * Ceph address space ops.
   *
   * There are a few funny things going on here.
   *
   * The page->private field is used to reference a struct
   * ceph_snap_context for _every_ dirty page.  This indicates which
   * snapshot the page was logically dirtied in, and thus which snap
   * context needs to be associated with the osd write during writeback.
   *
   * Similarly, struct ceph_inode_info maintains a set of counters to
   * count dirty pages on the inode.  In the absence of snapshots,
   * i_wrbuffer_ref == i_wrbuffer_ref_head == the dirty page count.
   *
   * When a snapshot is taken (that is, when the client receives
   * notification that a snapshot was taken), each inode with caps and
   * with dirty pages (dirty pages implies there is a cap) gets a new
   * ceph_cap_snap in the i_cap_snaps list (which is sorted in ascending
   * order, new snaps go to the tail).  The i_wrbuffer_ref_head count is
   * moved to capsnap->dirty. (Unless a sync write is currently in
   * progress.  In that case, the capsnap is said to be "pending", new
   * writes cannot start, and the capsnap isn't "finalized" until the
   * write completes (or fails) and a final size/mtime for the inode for
   * that snap can be settled upon.)  i_wrbuffer_ref_head is reset to 0.
   *
   * On writeback, we must submit writes to the osd IN SNAP ORDER.  So,
   * we look for the first capsnap in i_cap_snaps and write out pages in
   * that snap context _only_.  Then we move on to the next capsnap,
   * eventually reaching the "live" or "head" context (i.e., pages that
   * are not yet snapped) and are writing the most recently dirtied
   * pages.
   *
   * Invalidate and so forth must take care to ensure the dirty page
   * accounting is preserved.
   */
  
  #define CONGESTION_ON_THRESH(congestion_kb) (congestion_kb >> (PAGE_SHIFT-10))
  #define CONGESTION_OFF_THRESH(congestion_kb)				\
  	(CONGESTION_ON_THRESH(congestion_kb) -				\
  	 (CONGESTION_ON_THRESH(congestion_kb) >> 2))
  
  static inline struct ceph_snap_context *page_snap_context(struct page *page)
  {
  	if (PagePrivate(page))
  		return (void *)page->private;
  	return NULL;
  }
  
  /*
   * Dirty a page.  Optimistically adjust accounting, on the assumption
   * that we won't race with invalidate.  If we do, readjust.
   */
  static int ceph_set_page_dirty(struct page *page)
  {
  	struct address_space *mapping = page->mapping;
  	struct inode *inode;
  	struct ceph_inode_info *ci;
  	struct ceph_snap_context *snapc;
  	int ret;
  
  	if (unlikely(!mapping))
  		return !TestSetPageDirty(page);
  
  	if (PageDirty(page)) {
  		dout("%p set_page_dirty %p idx %lu -- already dirty\n",
  		     mapping->host, page, page->index);
  		BUG_ON(!PagePrivate(page));
  		return 0;
  	}
  
  	inode = mapping->host;
  	ci = ceph_inode(inode);
  
  	/* dirty the head */
  	spin_lock(&ci->i_ceph_lock);
  	BUG_ON(ci->i_wr_ref == 0); // caller should hold Fw reference
  	if (__ceph_have_pending_cap_snap(ci)) {
  		struct ceph_cap_snap *capsnap =
  				list_last_entry(&ci->i_cap_snaps,
  						struct ceph_cap_snap,
  						ci_item);
  		snapc = ceph_get_snap_context(capsnap->context);
  		capsnap->dirty_pages++;
  	} else {
  		BUG_ON(!ci->i_head_snapc);
  		snapc = ceph_get_snap_context(ci->i_head_snapc);
  		++ci->i_wrbuffer_ref_head;
  	}
  	if (ci->i_wrbuffer_ref == 0)
  		ihold(inode);
  	++ci->i_wrbuffer_ref;
  	dout("%p set_page_dirty %p idx %lu head %d/%d -> %d/%d "
  	     "snapc %p seq %lld (%d snaps)\n",
  	     mapping->host, page, page->index,
  	     ci->i_wrbuffer_ref-1, ci->i_wrbuffer_ref_head-1,
  	     ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
  	     snapc, snapc->seq, snapc->num_snaps);
  	spin_unlock(&ci->i_ceph_lock);
  
  	/*
  	 * Reference snap context in page->private.  Also set
  	 * PagePrivate so that we get invalidatepage callback.
  	 */
  	BUG_ON(PagePrivate(page));
  	page->private = (unsigned long)snapc;
  	SetPagePrivate(page);
  
  	ret = __set_page_dirty_nobuffers(page);
  	WARN_ON(!PageLocked(page));
  	WARN_ON(!page->mapping);
  
  	return ret;
  }
  
  /*
   * If we are truncating the full page (i.e. offset == 0), adjust the
   * dirty page counters appropriately.  Only called if there is private
   * data on the page.
   */
  static void ceph_invalidatepage(struct page *page, unsigned int offset,
  				unsigned int length)
  {
  	struct inode *inode;
  	struct ceph_inode_info *ci;
  	struct ceph_snap_context *snapc = page_snap_context(page);
  
  	inode = page->mapping->host;
  	ci = ceph_inode(inode);
  
  	if (offset != 0 || length != PAGE_SIZE) {
  		dout("%p invalidatepage %p idx %lu partial dirty page %u~%u\n",
  		     inode, page, page->index, offset, length);
  		return;
  	}
  
  	ceph_invalidate_fscache_page(inode, page);
  
  	WARN_ON(!PageLocked(page));
  	if (!PagePrivate(page))
  		return;
  
  	dout("%p invalidatepage %p idx %lu full dirty page\n",
  	     inode, page, page->index);
  
  	ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
  	ceph_put_snap_context(snapc);
  	page->private = 0;
  	ClearPagePrivate(page);
  }
  
  static int ceph_releasepage(struct page *page, gfp_t g)
  {
  	dout("%p releasepage %p idx %lu (%sdirty)\n", page->mapping->host,
  	     page, page->index, PageDirty(page) ? "" : "not ");
  
  	/* Can we release the page from the cache? */
  	if (!ceph_release_fscache_page(page, g))
  		return 0;
  
  	return !PagePrivate(page);
  }
  
  /* read a single page, without unlocking it. */
  static int ceph_do_readpage(struct file *filp, struct page *page)
  {
  	struct inode *inode = file_inode(filp);
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	struct ceph_osd_client *osdc = &fsc->client->osdc;
  	struct ceph_osd_request *req;
  	struct ceph_vino vino = ceph_vino(inode);
  	int err = 0;
  	u64 off = page_offset(page);
  	u64 len = PAGE_SIZE;
  
  	if (off >= i_size_read(inode)) {
  		zero_user_segment(page, 0, PAGE_SIZE);
  		SetPageUptodate(page);
  		return 0;
  	}
  
  	if (ci->i_inline_version != CEPH_INLINE_NONE) {
  		/*
  		 * Uptodate inline data should have been added
  		 * into page cache while getting Fcr caps.
  		 */
  		if (off == 0)
  			return -EINVAL;
  		zero_user_segment(page, 0, PAGE_SIZE);
  		SetPageUptodate(page);
  		return 0;
  	}
  
  	err = ceph_readpage_from_fscache(inode, page);
  	if (err == 0)
  		return -EINPROGRESS;
  
  	dout("readpage ino %llx.%llx file %p off %llu len %llu page %p index %lu\n",
  	     vino.ino, vino.snap, filp, off, len, page, page->index);
  	req = ceph_osdc_new_request(osdc, &ci->i_layout, vino, off, &len, 0, 1,
  				    CEPH_OSD_OP_READ, CEPH_OSD_FLAG_READ, NULL,
  				    ci->i_truncate_seq, ci->i_truncate_size,
  				    false);
  	if (IS_ERR(req))
  		return PTR_ERR(req);
  
  	osd_req_op_extent_osd_data_pages(req, 0, &page, len, 0, false, false);
  
  	err = ceph_osdc_start_request(osdc, req, false);
  	if (!err)
  		err = ceph_osdc_wait_request(osdc, req);
  
  	ceph_update_read_latency(&fsc->mdsc->metric, req->r_start_latency,
  				 req->r_end_latency, err);
  
  	ceph_osdc_put_request(req);
  	dout("readpage result %d\n", err);
  
  	if (err == -ENOENT)
  		err = 0;
  	if (err < 0) {
  		ceph_fscache_readpage_cancel(inode, page);
  		if (err == -EBLOCKLISTED)
  			fsc->blocklisted = true;
  		goto out;
  	}
  	if (err < PAGE_SIZE)
  		/* zero fill remainder of page */
  		zero_user_segment(page, err, PAGE_SIZE);
  	else
  		flush_dcache_page(page);
  
  	SetPageUptodate(page);
  	ceph_readpage_to_fscache(inode, page);
  
  out:
  	return err < 0 ? err : 0;
  }
  
  static int ceph_readpage(struct file *filp, struct page *page)
  {
  	int r = ceph_do_readpage(filp, page);
  	if (r != -EINPROGRESS)
  		unlock_page(page);
  	else
  		r = 0;
  	return r;
  }
  
  /*
   * Finish an async read(ahead) op.
   */
  static void finish_read(struct ceph_osd_request *req)
  {
  	struct inode *inode = req->r_inode;
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	struct ceph_osd_data *osd_data;
  	int rc = req->r_result <= 0 ? req->r_result : 0;
  	int bytes = req->r_result >= 0 ? req->r_result : 0;
  	int num_pages;
  	int i;
  
  	dout("finish_read %p req %p rc %d bytes %d\n", inode, req, rc, bytes);
  	if (rc == -EBLOCKLISTED)
  		ceph_inode_to_client(inode)->blocklisted = true;
  
  	/* unlock all pages, zeroing any data we didn't read */
  	osd_data = osd_req_op_extent_osd_data(req, 0);
  	BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_PAGES);
  	num_pages = calc_pages_for((u64)osd_data->alignment,
  					(u64)osd_data->length);
  	for (i = 0; i < num_pages; i++) {
  		struct page *page = osd_data->pages[i];
  
  		if (rc < 0 && rc != -ENOENT) {
  			ceph_fscache_readpage_cancel(inode, page);
  			goto unlock;
  		}
  		if (bytes < (int)PAGE_SIZE) {
  			/* zero (remainder of) page */
  			int s = bytes < 0 ? 0 : bytes;
  			zero_user_segment(page, s, PAGE_SIZE);
  		}
   		dout("finish_read %p uptodate %p idx %lu\n", inode, page,
  		     page->index);
  		flush_dcache_page(page);
  		SetPageUptodate(page);
  		ceph_readpage_to_fscache(inode, page);
  unlock:
  		unlock_page(page);
  		put_page(page);
  		bytes -= PAGE_SIZE;
  	}
  
  	ceph_update_read_latency(&fsc->mdsc->metric, req->r_start_latency,
  				 req->r_end_latency, rc);
  
  	kfree(osd_data->pages);
  }
  
  /*
   * start an async read(ahead) operation.  return nr_pages we submitted
   * a read for on success, or negative error code.
   */
  static int start_read(struct inode *inode, struct ceph_rw_context *rw_ctx,
  		      struct list_head *page_list, int max)
  {
  	struct ceph_osd_client *osdc =
  		&ceph_inode_to_client(inode)->client->osdc;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct page *page = lru_to_page(page_list);
  	struct ceph_vino vino;
  	struct ceph_osd_request *req;
  	u64 off;
  	u64 len;
  	int i;
  	struct page **pages;
  	pgoff_t next_index;
  	int nr_pages = 0;
  	int got = 0;
  	int ret = 0;
  
  	if (!rw_ctx) {
  		/* caller of readpages does not hold buffer and read caps
  		 * (fadvise, madvise and readahead cases) */
  		int want = CEPH_CAP_FILE_CACHE;
  		ret = ceph_try_get_caps(inode, CEPH_CAP_FILE_RD, want,
  					true, &got);
  		if (ret < 0) {
  			dout("start_read %p, error getting cap\n", inode);
  		} else if (!(got & want)) {
  			dout("start_read %p, no cache cap\n", inode);
  			ret = 0;
  		}
  		if (ret <= 0) {
  			if (got)
  				ceph_put_cap_refs(ci, got);
  			while (!list_empty(page_list)) {
  				page = lru_to_page(page_list);
  				list_del(&page->lru);
  				put_page(page);
  			}
  			return ret;
  		}
  	}
  
  	off = (u64) page_offset(page);
  
  	/* count pages */
  	next_index = page->index;
  	list_for_each_entry_reverse(page, page_list, lru) {
  		if (page->index != next_index)
  			break;
  		nr_pages++;
  		next_index++;
  		if (max && nr_pages == max)
  			break;
  	}
  	len = nr_pages << PAGE_SHIFT;
  	dout("start_read %p nr_pages %d is %lld~%lld\n", inode, nr_pages,
  	     off, len);
  	vino = ceph_vino(inode);
  	req = ceph_osdc_new_request(osdc, &ci->i_layout, vino, off, &len,
  				    0, 1, CEPH_OSD_OP_READ,
  				    CEPH_OSD_FLAG_READ, NULL,
  				    ci->i_truncate_seq, ci->i_truncate_size,
  				    false);
  	if (IS_ERR(req)) {
  		ret = PTR_ERR(req);
  		goto out;
  	}
  
  	/* build page vector */
  	nr_pages = calc_pages_for(0, len);
  	pages = kmalloc_array(nr_pages, sizeof(*pages), GFP_KERNEL);
  	if (!pages) {
  		ret = -ENOMEM;
  		goto out_put;
  	}
  	for (i = 0; i < nr_pages; ++i) {
  		page = list_entry(page_list->prev, struct page, lru);
  		BUG_ON(PageLocked(page));
  		list_del(&page->lru);
  
   		dout("start_read %p adding %p idx %lu\n", inode, page,
  		     page->index);
  		if (add_to_page_cache_lru(page, &inode->i_data, page->index,
  					  GFP_KERNEL)) {
  			ceph_fscache_uncache_page(inode, page);
  			put_page(page);
  			dout("start_read %p add_to_page_cache failed %p\n",
  			     inode, page);
  			nr_pages = i;
  			if (nr_pages > 0) {
  				len = nr_pages << PAGE_SHIFT;
  				osd_req_op_extent_update(req, 0, len);
  				break;
  			}
  			goto out_pages;
  		}
  		pages[i] = page;
  	}
  	osd_req_op_extent_osd_data_pages(req, 0, pages, len, 0, false, false);
  	req->r_callback = finish_read;
  	req->r_inode = inode;
  
  	dout("start_read %p starting %p %lld~%lld\n", inode, req, off, len);
  	ret = ceph_osdc_start_request(osdc, req, false);
  	if (ret < 0)
  		goto out_pages;
  	ceph_osdc_put_request(req);
  
  	/* After adding locked pages to page cache, the inode holds cache cap.
  	 * So we can drop our cap refs. */
  	if (got)
  		ceph_put_cap_refs(ci, got);
  
  	return nr_pages;
  
  out_pages:
  	for (i = 0; i < nr_pages; ++i) {
  		ceph_fscache_readpage_cancel(inode, pages[i]);
  		unlock_page(pages[i]);
  	}
  	ceph_put_page_vector(pages, nr_pages, false);
  out_put:
  	ceph_osdc_put_request(req);
  out:
  	if (got)
  		ceph_put_cap_refs(ci, got);
  	return ret;
  }
  
  
  /*
   * Read multiple pages.  Leave pages we don't read + unlock in page_list;
   * the caller (VM) cleans them up.
   */
  static int ceph_readpages(struct file *file, struct address_space *mapping,
  			  struct list_head *page_list, unsigned nr_pages)
  {
  	struct inode *inode = file_inode(file);
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	struct ceph_file_info *fi = file->private_data;
  	struct ceph_rw_context *rw_ctx;
  	int rc = 0;
  	int max = 0;
  
  	if (ceph_inode(inode)->i_inline_version != CEPH_INLINE_NONE)
  		return -EINVAL;
  
  	rc = ceph_readpages_from_fscache(mapping->host, mapping, page_list,
  					 &nr_pages);
  
  	if (rc == 0)
  		goto out;
  
  	rw_ctx = ceph_find_rw_context(fi);
  	max = fsc->mount_options->rsize >> PAGE_SHIFT;
  	dout("readpages %p file %p ctx %p nr_pages %d max %d\n",
  	     inode, file, rw_ctx, nr_pages, max);
  	while (!list_empty(page_list)) {
  		rc = start_read(inode, rw_ctx, page_list, max);
  		if (rc < 0)
  			goto out;
  	}
  out:
  	ceph_fscache_readpages_cancel(inode, page_list);
  
  	dout("readpages %p file %p ret %d\n", inode, file, rc);
  	return rc;
  }
  
  struct ceph_writeback_ctl
  {
  	loff_t i_size;
  	u64 truncate_size;
  	u32 truncate_seq;
  	bool size_stable;
  	bool head_snapc;
  };
  
  /*
   * Get ref for the oldest snapc for an inode with dirty data... that is, the
   * only snap context we are allowed to write back.
   */
  static struct ceph_snap_context *
  get_oldest_context(struct inode *inode, struct ceph_writeback_ctl *ctl,
  		   struct ceph_snap_context *page_snapc)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_snap_context *snapc = NULL;
  	struct ceph_cap_snap *capsnap = NULL;
  
  	spin_lock(&ci->i_ceph_lock);
  	list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
  		dout(" cap_snap %p snapc %p has %d dirty pages\n", capsnap,
  		     capsnap->context, capsnap->dirty_pages);
  		if (!capsnap->dirty_pages)
  			continue;
  
  		/* get i_size, truncate_{seq,size} for page_snapc? */
  		if (snapc && capsnap->context != page_snapc)
  			continue;
  
  		if (ctl) {
  			if (capsnap->writing) {
  				ctl->i_size = i_size_read(inode);
  				ctl->size_stable = false;
  			} else {
  				ctl->i_size = capsnap->size;
  				ctl->size_stable = true;
  			}
  			ctl->truncate_size = capsnap->truncate_size;
  			ctl->truncate_seq = capsnap->truncate_seq;
  			ctl->head_snapc = false;
  		}
  
  		if (snapc)
  			break;
  
  		snapc = ceph_get_snap_context(capsnap->context);
  		if (!page_snapc ||
  		    page_snapc == snapc ||
  		    page_snapc->seq > snapc->seq)
  			break;
  	}
  	if (!snapc && ci->i_wrbuffer_ref_head) {
  		snapc = ceph_get_snap_context(ci->i_head_snapc);
  		dout(" head snapc %p has %d dirty pages\n",
  		     snapc, ci->i_wrbuffer_ref_head);
  		if (ctl) {
  			ctl->i_size = i_size_read(inode);
  			ctl->truncate_size = ci->i_truncate_size;
  			ctl->truncate_seq = ci->i_truncate_seq;
  			ctl->size_stable = false;
  			ctl->head_snapc = true;
  		}
  	}
  	spin_unlock(&ci->i_ceph_lock);
  	return snapc;
  }
  
  static u64 get_writepages_data_length(struct inode *inode,
  				      struct page *page, u64 start)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_snap_context *snapc = page_snap_context(page);
  	struct ceph_cap_snap *capsnap = NULL;
  	u64 end = i_size_read(inode);
  
  	if (snapc != ci->i_head_snapc) {
  		bool found = false;
  		spin_lock(&ci->i_ceph_lock);
  		list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
  			if (capsnap->context == snapc) {
  				if (!capsnap->writing)
  					end = capsnap->size;
  				found = true;
  				break;
  			}
  		}
  		spin_unlock(&ci->i_ceph_lock);
  		WARN_ON(!found);
  	}
  	if (end > page_offset(page) + PAGE_SIZE)
  		end = page_offset(page) + PAGE_SIZE;
  	return end > start ? end - start : 0;
  }
  
  /*
   * Write a single page, but leave the page locked.
   *
   * If we get a write error, mark the mapping for error, but still adjust the
   * dirty page accounting (i.e., page is no longer dirty).
   */
  static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
  {
  	struct inode *inode = page->mapping->host;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	struct ceph_snap_context *snapc, *oldest;
  	loff_t page_off = page_offset(page);
  	int err;
  	loff_t len = PAGE_SIZE;
  	struct ceph_writeback_ctl ceph_wbc;
  	struct ceph_osd_client *osdc = &fsc->client->osdc;
  	struct ceph_osd_request *req;
  
  	dout("writepage %p idx %lu\n", page, page->index);
  
  	/* verify this is a writeable snap context */
  	snapc = page_snap_context(page);
  	if (!snapc) {
  		dout("writepage %p page %p not dirty?\n", inode, page);
  		return 0;
  	}
  	oldest = get_oldest_context(inode, &ceph_wbc, snapc);
  	if (snapc->seq > oldest->seq) {
  		dout("writepage %p page %p snapc %p not writeable - noop\n",
  		     inode, page, snapc);
  		/* we should only noop if called by kswapd */
  		WARN_ON(!(current->flags & PF_MEMALLOC));
  		ceph_put_snap_context(oldest);
  		redirty_page_for_writepage(wbc, page);
  		return 0;
  	}
  	ceph_put_snap_context(oldest);
  
  	/* is this a partial page at end of file? */
  	if (page_off >= ceph_wbc.i_size) {
  		dout("%p page eof %llu\n", page, ceph_wbc.i_size);
  		page->mapping->a_ops->invalidatepage(page, 0, PAGE_SIZE);
  		return 0;
  	}
  
  	if (ceph_wbc.i_size < page_off + len)
  		len = ceph_wbc.i_size - page_off;
  
  	dout("writepage %p page %p index %lu on %llu~%llu snapc %p seq %lld\n",
  	     inode, page, page->index, page_off, len, snapc, snapc->seq);
  
  	if (atomic_long_inc_return(&fsc->writeback_count) >
  	    CONGESTION_ON_THRESH(fsc->mount_options->congestion_kb))
  		set_bdi_congested(inode_to_bdi(inode), BLK_RW_ASYNC);
  
  	set_page_writeback(page);
  	req = ceph_osdc_new_request(osdc, &ci->i_layout, ceph_vino(inode), page_off, &len, 0, 1,
  				    CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE, snapc,
  				    ceph_wbc.truncate_seq, ceph_wbc.truncate_size,
  				    true);
  	if (IS_ERR(req)) {
  		redirty_page_for_writepage(wbc, page);
  		end_page_writeback(page);
  		return PTR_ERR(req);
  	}
  
  	/* it may be a short write due to an object boundary */
  	WARN_ON_ONCE(len > PAGE_SIZE);
  	osd_req_op_extent_osd_data_pages(req, 0, &page, len, 0, false, false);
  	dout("writepage %llu~%llu (%llu bytes)\n", page_off, len, len);
  
  	req->r_mtime = inode->i_mtime;
  	err = ceph_osdc_start_request(osdc, req, true);
  	if (!err)
  		err = ceph_osdc_wait_request(osdc, req);
  
  	ceph_update_write_latency(&fsc->mdsc->metric, req->r_start_latency,
  				  req->r_end_latency, err);
  
  	ceph_osdc_put_request(req);
  	if (err == 0)
  		err = len;
  
  	if (err < 0) {
  		struct writeback_control tmp_wbc;
  		if (!wbc)
  			wbc = &tmp_wbc;
  		if (err == -ERESTARTSYS) {
  			/* killed by SIGKILL */
  			dout("writepage interrupted page %p\n", page);
  			redirty_page_for_writepage(wbc, page);
  			end_page_writeback(page);
  			return err;
  		}
  		if (err == -EBLOCKLISTED)
  			fsc->blocklisted = true;
  		dout("writepage setting page/mapping error %d %p\n",
  		     err, page);
  		mapping_set_error(&inode->i_data, err);
  		wbc->pages_skipped++;
  	} else {
  		dout("writepage cleaned page %p\n", page);
  		err = 0;  /* vfs expects us to return 0 */
  	}
  	page->private = 0;
  	ClearPagePrivate(page);
  	end_page_writeback(page);
  	ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
  	ceph_put_snap_context(snapc);  /* page's reference */
  
  	if (atomic_long_dec_return(&fsc->writeback_count) <
  	    CONGESTION_OFF_THRESH(fsc->mount_options->congestion_kb))
  		clear_bdi_congested(inode_to_bdi(inode), BLK_RW_ASYNC);
  
  	return err;
  }
  
  static int ceph_writepage(struct page *page, struct writeback_control *wbc)
  {
  	int err;
  	struct inode *inode = page->mapping->host;
  	BUG_ON(!inode);
  	ihold(inode);
  	err = writepage_nounlock(page, wbc);
  	if (err == -ERESTARTSYS) {
  		/* direct memory reclaimer was killed by SIGKILL. return 0
  		 * to prevent caller from setting mapping/page error */
  		err = 0;
  	}
  	unlock_page(page);
  	iput(inode);
  	return err;
  }
  
  /*
   * async writeback completion handler.
   *
   * If we get an error, set the mapping error bit, but not the individual
   * page error bits.
   */
  static void writepages_finish(struct ceph_osd_request *req)
  {
  	struct inode *inode = req->r_inode;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_osd_data *osd_data;
  	struct page *page;
  	int num_pages, total_pages = 0;
  	int i, j;
  	int rc = req->r_result;
  	struct ceph_snap_context *snapc = req->r_snapc;
  	struct address_space *mapping = inode->i_mapping;
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	bool remove_page;
  
  	dout("writepages_finish %p rc %d\n", inode, rc);
  	if (rc < 0) {
  		mapping_set_error(mapping, rc);
  		ceph_set_error_write(ci);
  		if (rc == -EBLOCKLISTED)
  			fsc->blocklisted = true;
  	} else {
  		ceph_clear_error_write(ci);
  	}
  
  	ceph_update_write_latency(&fsc->mdsc->metric, req->r_start_latency,
  				  req->r_end_latency, rc);
  
  	/*
  	 * We lost the cache cap, need to truncate the page before
  	 * it is unlocked, otherwise we'd truncate it later in the
  	 * page truncation thread, possibly losing some data that
  	 * raced its way in
  	 */
  	remove_page = !(ceph_caps_issued(ci) &
  			(CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO));
  
  	/* clean all pages */
  	for (i = 0; i < req->r_num_ops; i++) {
  		if (req->r_ops[i].op != CEPH_OSD_OP_WRITE)
  			break;
  
  		osd_data = osd_req_op_extent_osd_data(req, i);
  		BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_PAGES);
  		num_pages = calc_pages_for((u64)osd_data->alignment,
  					   (u64)osd_data->length);
  		total_pages += num_pages;
  		for (j = 0; j < num_pages; j++) {
  			page = osd_data->pages[j];
  			BUG_ON(!page);
  			WARN_ON(!PageUptodate(page));
  
  			if (atomic_long_dec_return(&fsc->writeback_count) <
  			     CONGESTION_OFF_THRESH(
  					fsc->mount_options->congestion_kb))
  				clear_bdi_congested(inode_to_bdi(inode),
  						    BLK_RW_ASYNC);
  
  			ceph_put_snap_context(page_snap_context(page));
  			page->private = 0;
  			ClearPagePrivate(page);
  			dout("unlocking %p\n", page);
  			end_page_writeback(page);
  
  			if (remove_page)
  				generic_error_remove_page(inode->i_mapping,
  							  page);
  
  			unlock_page(page);
  		}
  		dout("writepages_finish %p wrote %llu bytes cleaned %d pages\n",
  		     inode, osd_data->length, rc >= 0 ? num_pages : 0);
  
  		release_pages(osd_data->pages, num_pages);
  	}
  
  	ceph_put_wrbuffer_cap_refs(ci, total_pages, snapc);
  
  	osd_data = osd_req_op_extent_osd_data(req, 0);
  	if (osd_data->pages_from_pool)
  		mempool_free(osd_data->pages, ceph_wb_pagevec_pool);
  	else
  		kfree(osd_data->pages);
  	ceph_osdc_put_request(req);
  }
  
  /*
   * initiate async writeback
   */
  static int ceph_writepages_start(struct address_space *mapping,
  				 struct writeback_control *wbc)
  {
  	struct inode *inode = mapping->host;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	struct ceph_vino vino = ceph_vino(inode);
  	pgoff_t index, start_index, end = -1;
  	struct ceph_snap_context *snapc = NULL, *last_snapc = NULL, *pgsnapc;
  	struct pagevec pvec;
  	int rc = 0;
  	unsigned int wsize = i_blocksize(inode);
  	struct ceph_osd_request *req = NULL;
  	struct ceph_writeback_ctl ceph_wbc;
  	bool should_loop, range_whole = false;
  	bool done = false;
  
  	dout("writepages_start %p (mode=%s)\n", inode,
  	     wbc->sync_mode == WB_SYNC_NONE ? "NONE" :
  	     (wbc->sync_mode == WB_SYNC_ALL ? "ALL" : "HOLD"));
  
  	if (READ_ONCE(fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
  		if (ci->i_wrbuffer_ref > 0) {
  			pr_warn_ratelimited(
  				"writepage_start %p %lld forced umount\n",
  				inode, ceph_ino(inode));
  		}
  		mapping_set_error(mapping, -EIO);
  		return -EIO; /* we're in a forced umount, don't write! */
  	}
  	if (fsc->mount_options->wsize < wsize)
  		wsize = fsc->mount_options->wsize;
  
  	pagevec_init(&pvec);
  
  	start_index = wbc->range_cyclic ? mapping->writeback_index : 0;
  	index = start_index;
  
  retry:
  	/* find oldest snap context with dirty data */
  	snapc = get_oldest_context(inode, &ceph_wbc, NULL);
  	if (!snapc) {
  		/* hmm, why does writepages get called when there
  		   is no dirty data? */
  		dout(" no snap context with dirty data?\n");
  		goto out;
  	}
  	dout(" oldest snapc is %p seq %lld (%d snaps)\n",
  	     snapc, snapc->seq, snapc->num_snaps);
  
  	should_loop = false;
  	if (ceph_wbc.head_snapc && snapc != last_snapc) {
  		/* where to start/end? */
  		if (wbc->range_cyclic) {
  			index = start_index;
  			end = -1;
  			if (index > 0)
  				should_loop = true;
  			dout(" cyclic, start at %lu\n", index);
  		} else {
  			index = wbc->range_start >> PAGE_SHIFT;
  			end = wbc->range_end >> PAGE_SHIFT;
  			if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
  				range_whole = true;
  			dout(" not cyclic, %lu to %lu\n", index, end);
  		}
  	} else if (!ceph_wbc.head_snapc) {
  		/* Do not respect wbc->range_{start,end}. Dirty pages
  		 * in that range can be associated with newer snapc.
  		 * They are not writeable until we write all dirty pages
  		 * associated with 'snapc' get written */
  		if (index > 0)
  			should_loop = true;
  		dout(" non-head snapc, range whole\n");
  	}
  
  	ceph_put_snap_context(last_snapc);
  	last_snapc = snapc;
  
  	while (!done && index <= end) {
  		int num_ops = 0, op_idx;
  		unsigned i, pvec_pages, max_pages, locked_pages = 0;
  		struct page **pages = NULL, **data_pages;
  		struct page *page;
  		pgoff_t strip_unit_end = 0;
  		u64 offset = 0, len = 0;
  		bool from_pool = false;
  
  		max_pages = wsize >> PAGE_SHIFT;
  
  get_more_pages:
  		pvec_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
  						end, PAGECACHE_TAG_DIRTY);
  		dout("pagevec_lookup_range_tag got %d\n", pvec_pages);
  		if (!pvec_pages && !locked_pages)
  			break;
  		for (i = 0; i < pvec_pages && locked_pages < max_pages; i++) {
  			page = pvec.pages[i];
  			dout("? %p idx %lu\n", page, page->index);
  			if (locked_pages == 0)
  				lock_page(page);  /* first page */
  			else if (!trylock_page(page))
  				break;
  
  			/* only dirty pages, or our accounting breaks */
  			if (unlikely(!PageDirty(page)) ||
  			    unlikely(page->mapping != mapping)) {
  				dout("!dirty or !mapping %p\n", page);
  				unlock_page(page);
  				continue;
  			}
  			/* only if matching snap context */
  			pgsnapc = page_snap_context(page);
  			if (pgsnapc != snapc) {
  				dout("page snapc %p %lld != oldest %p %lld\n",
  				     pgsnapc, pgsnapc->seq, snapc, snapc->seq);
  				if (!should_loop &&
  				    !ceph_wbc.head_snapc &&
  				    wbc->sync_mode != WB_SYNC_NONE)
  					should_loop = true;
  				unlock_page(page);
  				continue;
  			}
  			if (page_offset(page) >= ceph_wbc.i_size) {
  				dout("%p page eof %llu\n",
  				     page, ceph_wbc.i_size);
  				if ((ceph_wbc.size_stable ||
  				    page_offset(page) >= i_size_read(inode)) &&
  				    clear_page_dirty_for_io(page))
  					mapping->a_ops->invalidatepage(page,
  								0, PAGE_SIZE);
  				unlock_page(page);
  				continue;
  			}
  			if (strip_unit_end && (page->index > strip_unit_end)) {
  				dout("end of strip unit %p\n", page);
  				unlock_page(page);
  				break;
  			}
  			if (PageWriteback(page)) {
  				if (wbc->sync_mode == WB_SYNC_NONE) {
  					dout("%p under writeback\n", page);
  					unlock_page(page);
  					continue;
  				}
  				dout("waiting on writeback %p\n", page);
  				wait_on_page_writeback(page);
  			}
  
  			if (!clear_page_dirty_for_io(page)) {
  				dout("%p !clear_page_dirty_for_io\n", page);
  				unlock_page(page);
  				continue;
  			}
  
  			/*
  			 * We have something to write.  If this is
  			 * the first locked page this time through,
  			 * calculate max possinle write size and
  			 * allocate a page array
  			 */
  			if (locked_pages == 0) {
  				u64 objnum;
  				u64 objoff;
  				u32 xlen;
  
  				/* prepare async write request */
  				offset = (u64)page_offset(page);
  				ceph_calc_file_object_mapping(&ci->i_layout,
  							      offset, wsize,
  							      &objnum, &objoff,
  							      &xlen);
  				len = xlen;
  
  				num_ops = 1;
  				strip_unit_end = page->index +
  					((len - 1) >> PAGE_SHIFT);
  
  				BUG_ON(pages);
  				max_pages = calc_pages_for(0, (u64)len);
  				pages = kmalloc_array(max_pages,
  						      sizeof(*pages),
  						      GFP_NOFS);
  				if (!pages) {
  					from_pool = true;
  					pages = mempool_alloc(ceph_wb_pagevec_pool, GFP_NOFS);
  					BUG_ON(!pages);
  				}
  
  				len = 0;
  			} else if (page->index !=
  				   (offset + len) >> PAGE_SHIFT) {
  				if (num_ops >= (from_pool ?  CEPH_OSD_SLAB_OPS :
  							     CEPH_OSD_MAX_OPS)) {
  					redirty_page_for_writepage(wbc, page);
  					unlock_page(page);
  					break;
  				}
  
  				num_ops++;
  				offset = (u64)page_offset(page);
  				len = 0;
  			}
  
  			/* note position of first page in pvec */
  			dout("%p will write page %p idx %lu\n",
  			     inode, page, page->index);
  
  			if (atomic_long_inc_return(&fsc->writeback_count) >
  			    CONGESTION_ON_THRESH(
  				    fsc->mount_options->congestion_kb)) {
  				set_bdi_congested(inode_to_bdi(inode),
  						  BLK_RW_ASYNC);
  			}
  
  
  			pages[locked_pages++] = page;
  			pvec.pages[i] = NULL;
  
  			len += PAGE_SIZE;
  		}
  
  		/* did we get anything? */
  		if (!locked_pages)
  			goto release_pvec_pages;
  		if (i) {
  			unsigned j, n = 0;
  			/* shift unused page to beginning of pvec */
  			for (j = 0; j < pvec_pages; j++) {
  				if (!pvec.pages[j])
  					continue;
  				if (n < j)
  					pvec.pages[n] = pvec.pages[j];
  				n++;
  			}
  			pvec.nr = n;
  
  			if (pvec_pages && i == pvec_pages &&
  			    locked_pages < max_pages) {
  				dout("reached end pvec, trying for more\n");
  				pagevec_release(&pvec);
  				goto get_more_pages;
  			}
  		}
  
  new_request:
  		offset = page_offset(pages[0]);
  		len = wsize;
  
  		req = ceph_osdc_new_request(&fsc->client->osdc,
  					&ci->i_layout, vino,
  					offset, &len, 0, num_ops,
  					CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
  					snapc, ceph_wbc.truncate_seq,
  					ceph_wbc.truncate_size, false);
  		if (IS_ERR(req)) {
  			req = ceph_osdc_new_request(&fsc->client->osdc,
  						&ci->i_layout, vino,
  						offset, &len, 0,
  						min(num_ops,
  						    CEPH_OSD_SLAB_OPS),
  						CEPH_OSD_OP_WRITE,
  						CEPH_OSD_FLAG_WRITE,
  						snapc, ceph_wbc.truncate_seq,
  						ceph_wbc.truncate_size, true);
  			BUG_ON(IS_ERR(req));
  		}
  		BUG_ON(len < page_offset(pages[locked_pages - 1]) +
  			     PAGE_SIZE - offset);
  
  		req->r_callback = writepages_finish;
  		req->r_inode = inode;
  
  		/* Format the osd request message and submit the write */
  		len = 0;
  		data_pages = pages;
  		op_idx = 0;
  		for (i = 0; i < locked_pages; i++) {
  			u64 cur_offset = page_offset(pages[i]);
  			if (offset + len != cur_offset) {
  				if (op_idx + 1 == req->r_num_ops)
  					break;
  				osd_req_op_extent_dup_last(req, op_idx,
  							   cur_offset - offset);
  				dout("writepages got pages at %llu~%llu\n",
  				     offset, len);
  				osd_req_op_extent_osd_data_pages(req, op_idx,
  							data_pages, len, 0,
  							from_pool, false);
  				osd_req_op_extent_update(req, op_idx, len);
  
  				len = 0;
  				offset = cur_offset; 
  				data_pages = pages + i;
  				op_idx++;
  			}
  
  			set_page_writeback(pages[i]);
  			len += PAGE_SIZE;
  		}
  
  		if (ceph_wbc.size_stable) {
  			len = min(len, ceph_wbc.i_size - offset);
  		} else if (i == locked_pages) {
  			/* writepages_finish() clears writeback pages
  			 * according to the data length, so make sure
  			 * data length covers all locked pages */
  			u64 min_len = len + 1 - PAGE_SIZE;
  			len = get_writepages_data_length(inode, pages[i - 1],
  							 offset);
  			len = max(len, min_len);
  		}
  		dout("writepages got pages at %llu~%llu\n", offset, len);
  
  		osd_req_op_extent_osd_data_pages(req, op_idx, data_pages, len,
  						 0, from_pool, false);
  		osd_req_op_extent_update(req, op_idx, len);
  
  		BUG_ON(op_idx + 1 != req->r_num_ops);
  
  		from_pool = false;
  		if (i < locked_pages) {
  			BUG_ON(num_ops <= req->r_num_ops);
  			num_ops -= req->r_num_ops;
  			locked_pages -= i;
  
  			/* allocate new pages array for next request */
  			data_pages = pages;
  			pages = kmalloc_array(locked_pages, sizeof(*pages),
  					      GFP_NOFS);
  			if (!pages) {
  				from_pool = true;
  				pages = mempool_alloc(ceph_wb_pagevec_pool, GFP_NOFS);
  				BUG_ON(!pages);
  			}
  			memcpy(pages, data_pages + i,
  			       locked_pages * sizeof(*pages));
  			memset(data_pages + i, 0,
  			       locked_pages * sizeof(*pages));
  		} else {
  			BUG_ON(num_ops != req->r_num_ops);
  			index = pages[i - 1]->index + 1;
  			/* request message now owns the pages array */
  			pages = NULL;
  		}
  
  		req->r_mtime = inode->i_mtime;
  		rc = ceph_osdc_start_request(&fsc->client->osdc, req, true);
  		BUG_ON(rc);
  		req = NULL;
  
  		wbc->nr_to_write -= i;
  		if (pages)
  			goto new_request;
  
  		/*
  		 * We stop writing back only if we are not doing
  		 * integrity sync. In case of integrity sync we have to
  		 * keep going until we have written all the pages
  		 * we tagged for writeback prior to entering this loop.
  		 */
  		if (wbc->nr_to_write <= 0 && wbc->sync_mode == WB_SYNC_NONE)
  			done = true;
  
  release_pvec_pages:
  		dout("pagevec_release on %d pages (%p)\n", (int)pvec.nr,
  		     pvec.nr ? pvec.pages[0] : NULL);
  		pagevec_release(&pvec);
  	}
  
  	if (should_loop && !done) {
  		/* more to do; loop back to beginning of file */
  		dout("writepages looping back to beginning of file\n");
  		end = start_index - 1; /* OK even when start_index == 0 */
  
  		/* to write dirty pages associated with next snapc,
  		 * we need to wait until current writes complete */
  		if (wbc->sync_mode != WB_SYNC_NONE &&
  		    start_index == 0 && /* all dirty pages were checked */
  		    !ceph_wbc.head_snapc) {
  			struct page *page;
  			unsigned i, nr;
  			index = 0;
  			while ((index <= end) &&
  			       (nr = pagevec_lookup_tag(&pvec, mapping, &index,
  						PAGECACHE_TAG_WRITEBACK))) {
  				for (i = 0; i < nr; i++) {
  					page = pvec.pages[i];
  					if (page_snap_context(page) != snapc)
  						continue;
  					wait_on_page_writeback(page);
  				}
  				pagevec_release(&pvec);
  				cond_resched();
  			}
  		}
  
  		start_index = 0;
  		index = 0;
  		goto retry;
  	}
  
  	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
  		mapping->writeback_index = index;
  
  out:
  	ceph_osdc_put_request(req);
  	ceph_put_snap_context(last_snapc);
  	dout("writepages dend - startone, rc = %d\n", rc);
  	return rc;
  }
  
  
  
  /*
   * See if a given @snapc is either writeable, or already written.
   */
  static int context_is_writeable_or_written(struct inode *inode,
  					   struct ceph_snap_context *snapc)
  {
  	struct ceph_snap_context *oldest = get_oldest_context(inode, NULL, NULL);
  	int ret = !oldest || snapc->seq <= oldest->seq;
  
  	ceph_put_snap_context(oldest);
  	return ret;
  }
  
  /**
   * ceph_find_incompatible - find an incompatible context and return it
   * @page: page being dirtied
   *
   * We are only allowed to write into/dirty a page if the page is
   * clean, or already dirty within the same snap context. Returns a
   * conflicting context if there is one, NULL if there isn't, or a
   * negative error code on other errors.
   *
   * Must be called with page lock held.
   */
  static struct ceph_snap_context *
  ceph_find_incompatible(struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	struct ceph_inode_info *ci = ceph_inode(inode);
  
  	if (READ_ONCE(fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
  		dout(" page %p forced umount\n", page);
  		return ERR_PTR(-EIO);
  	}
  
  	for (;;) {
  		struct ceph_snap_context *snapc, *oldest;
  
  		wait_on_page_writeback(page);
  
  		snapc = page_snap_context(page);
  		if (!snapc || snapc == ci->i_head_snapc)
  			break;
  
  		/*
  		 * this page is already dirty in another (older) snap
  		 * context!  is it writeable now?
  		 */
  		oldest = get_oldest_context(inode, NULL, NULL);
  		if (snapc->seq > oldest->seq) {
  			/* not writeable -- return it for the caller to deal with */
  			ceph_put_snap_context(oldest);
  			dout(" page %p snapc %p not current or oldest\n", page, snapc);
  			return ceph_get_snap_context(snapc);
  		}
  		ceph_put_snap_context(oldest);
  
  		/* yay, writeable, do it now (without dropping page lock) */
  		dout(" page %p snapc %p not current, but oldest\n", page, snapc);
  		if (clear_page_dirty_for_io(page)) {
  			int r = writepage_nounlock(page, NULL);
  			if (r < 0)
  				return ERR_PTR(r);
  		}
  	}
  	return NULL;
  }
  
  /*
   * We are only allowed to write into/dirty the page if the page is
   * clean, or already dirty within the same snap context.
   */
  static int ceph_write_begin(struct file *file, struct address_space *mapping,
  			    loff_t pos, unsigned len, unsigned flags,
  			    struct page **pagep, void **fsdata)
  {
  	struct inode *inode = file_inode(file);
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_snap_context *snapc;
  	struct page *page = NULL;
  	pgoff_t index = pos >> PAGE_SHIFT;
  	int pos_in_page = pos & ~PAGE_MASK;
  	int r = 0;
  
  	dout("write_begin file %p inode %p page %p %d~%d\n", file, inode, page, (int)pos, (int)len);
  
  	for (;;) {
  		page = grab_cache_page_write_begin(mapping, index, 0);
  		if (!page) {
  			r = -ENOMEM;
  			break;
  		}
  
  		snapc = ceph_find_incompatible(page);
  		if (snapc) {
  			if (IS_ERR(snapc)) {
  				r = PTR_ERR(snapc);
  				break;
  			}
  			unlock_page(page);
  			put_page(page);
  			page = NULL;
  			ceph_queue_writeback(inode);
  			r = wait_event_killable(ci->i_cap_wq,
  						context_is_writeable_or_written(inode, snapc));
  			ceph_put_snap_context(snapc);
  			if (r != 0)
  				break;
  			continue;
  		}
  
  		if (PageUptodate(page)) {
  			dout(" page %p already uptodate\n", page);
  			break;
  		}
  
  		/*
  		 * In some cases we don't need to read at all:
  		 * - full page write
  		 * - write that lies completely beyond EOF
  		 * - write that covers the the page from start to EOF or beyond it
  		 */
  		if ((pos_in_page == 0 && len == PAGE_SIZE) ||
  		    (pos >= i_size_read(inode)) ||
  		    (pos_in_page == 0 && (pos + len) >= i_size_read(inode))) {
  			zero_user_segments(page, 0, pos_in_page,
  					   pos_in_page + len, PAGE_SIZE);
  			break;
  		}
  
  		/*
  		 * We need to read it. If we get back -EINPROGRESS, then the page was
  		 * handed off to fscache and it will be unlocked when the read completes.
  		 * Refind the page in that case so we can reacquire the page lock. Otherwise
  		 * we got a hard error or the read was completed synchronously.
  		 */
  		r = ceph_do_readpage(file, page);
  		if (r != -EINPROGRESS)
  			break;
  	}
  
  	if (r < 0) {
  		if (page) {
  			unlock_page(page);
  			put_page(page);
  		}
  	} else {
  		*pagep = page;
  	}
  	return r;
  }
  
  /*
   * we don't do anything in here that simple_write_end doesn't do
   * except adjust dirty page accounting
   */
  static int ceph_write_end(struct file *file, struct address_space *mapping,
  			  loff_t pos, unsigned len, unsigned copied,
  			  struct page *page, void *fsdata)
  {
  	struct inode *inode = file_inode(file);
  	bool check_cap = false;
  
  	dout("write_end file %p inode %p page %p %d~%d (%d)\n", file,
  	     inode, page, (int)pos, (int)copied, (int)len);
  
  	/* zero the stale part of the page if we did a short copy */
  	if (!PageUptodate(page)) {
  		if (copied < len) {
  			copied = 0;
  			goto out;
  		}
  		SetPageUptodate(page);
  	}
  
  	/* did file size increase? */
  	if (pos+copied > i_size_read(inode))
  		check_cap = ceph_inode_set_size(inode, pos+copied);
  
  	set_page_dirty(page);
  
  out:
  	unlock_page(page);
  	put_page(page);
  
  	if (check_cap)
  		ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY, NULL);
  
  	return copied;
  }
  
  /*
   * we set .direct_IO to indicate direct io is supported, but since we
   * intercept O_DIRECT reads and writes early, this function should
   * never get called.
   */
  static ssize_t ceph_direct_io(struct kiocb *iocb, struct iov_iter *iter)
  {
  	WARN_ON(1);
  	return -EINVAL;
  }
  
  const struct address_space_operations ceph_aops = {
  	.readpage = ceph_readpage,
  	.readpages = ceph_readpages,
  	.writepage = ceph_writepage,
  	.writepages = ceph_writepages_start,
  	.write_begin = ceph_write_begin,
  	.write_end = ceph_write_end,
  	.set_page_dirty = ceph_set_page_dirty,
  	.invalidatepage = ceph_invalidatepage,
  	.releasepage = ceph_releasepage,
  	.direct_IO = ceph_direct_io,
  };
  
  static void ceph_block_sigs(sigset_t *oldset)
  {
  	sigset_t mask;
  	siginitsetinv(&mask, sigmask(SIGKILL));
  	sigprocmask(SIG_BLOCK, &mask, oldset);
  }
  
  static void ceph_restore_sigs(sigset_t *oldset)
  {
  	sigprocmask(SIG_SETMASK, oldset, NULL);
  }
  
  /*
   * vm ops
   */
  static vm_fault_t ceph_filemap_fault(struct vm_fault *vmf)
  {
  	struct vm_area_struct *vma = vmf->vma;
  	struct inode *inode = file_inode(vma->vm_file);
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_file_info *fi = vma->vm_file->private_data;
  	struct page *pinned_page = NULL;
  	loff_t off = (loff_t)vmf->pgoff << PAGE_SHIFT;
  	int want, got, err;
  	sigset_t oldset;
  	vm_fault_t ret = VM_FAULT_SIGBUS;
  
  	ceph_block_sigs(&oldset);
  
  	dout("filemap_fault %p %llx.%llx %llu~%zd trying to get caps\n",
  	     inode, ceph_vinop(inode), off, (size_t)PAGE_SIZE);
  	if (fi->fmode & CEPH_FILE_MODE_LAZY)
  		want = CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO;
  	else
  		want = CEPH_CAP_FILE_CACHE;
  
  	got = 0;
  	err = ceph_get_caps(vma->vm_file, CEPH_CAP_FILE_RD, want, -1,
  			    &got, &pinned_page);
  	if (err < 0)
  		goto out_restore;
  
  	dout("filemap_fault %p %llu~%zd got cap refs on %s\n",
  	     inode, off, (size_t)PAGE_SIZE, ceph_cap_string(got));
  
  	if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) ||
  	    ci->i_inline_version == CEPH_INLINE_NONE) {
  		CEPH_DEFINE_RW_CONTEXT(rw_ctx, got);
  		ceph_add_rw_context(fi, &rw_ctx);
  		ret = filemap_fault(vmf);
  		ceph_del_rw_context(fi, &rw_ctx);
  		dout("filemap_fault %p %llu~%zd drop cap refs %s ret %x\n",
  			inode, off, (size_t)PAGE_SIZE,
  				ceph_cap_string(got), ret);
  	} else
  		err = -EAGAIN;
  
  	if (pinned_page)
  		put_page(pinned_page);
  	ceph_put_cap_refs(ci, got);
  
  	if (err != -EAGAIN)
  		goto out_restore;
  
  	/* read inline data */
  	if (off >= PAGE_SIZE) {
  		/* does not support inline data > PAGE_SIZE */
  		ret = VM_FAULT_SIGBUS;
  	} else {
  		struct address_space *mapping = inode->i_mapping;
  		struct page *page = find_or_create_page(mapping, 0,
  						mapping_gfp_constraint(mapping,
  						~__GFP_FS));
  		if (!page) {
  			ret = VM_FAULT_OOM;
  			goto out_inline;
  		}
  		err = __ceph_do_getattr(inode, page,
  					 CEPH_STAT_CAP_INLINE_DATA, true);
  		if (err < 0 || off >= i_size_read(inode)) {
  			unlock_page(page);
  			put_page(page);
  			ret = vmf_error(err);
  			goto out_inline;
  		}
  		if (err < PAGE_SIZE)
  			zero_user_segment(page, err, PAGE_SIZE);
  		else
  			flush_dcache_page(page);
  		SetPageUptodate(page);
  		vmf->page = page;
  		ret = VM_FAULT_MAJOR | VM_FAULT_LOCKED;
  out_inline:
  		dout("filemap_fault %p %llu~%zd read inline data ret %x\n",
  		     inode, off, (size_t)PAGE_SIZE, ret);
  	}
  out_restore:
  	ceph_restore_sigs(&oldset);
  	if (err < 0)
  		ret = vmf_error(err);
  
  	return ret;
  }
  
  /*
   * Reuse write_begin here for simplicity.
   */
  static vm_fault_t ceph_page_mkwrite(struct vm_fault *vmf)
  {
  	struct vm_area_struct *vma = vmf->vma;
  	struct inode *inode = file_inode(vma->vm_file);
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_file_info *fi = vma->vm_file->private_data;
  	struct ceph_cap_flush *prealloc_cf;
  	struct page *page = vmf->page;
  	loff_t off = page_offset(page);
  	loff_t size = i_size_read(inode);
  	size_t len;
  	int want, got, err;
  	sigset_t oldset;
  	vm_fault_t ret = VM_FAULT_SIGBUS;
  
  	prealloc_cf = ceph_alloc_cap_flush();
  	if (!prealloc_cf)
  		return VM_FAULT_OOM;
  
  	sb_start_pagefault(inode->i_sb);
  	ceph_block_sigs(&oldset);
  
  	if (ci->i_inline_version != CEPH_INLINE_NONE) {
  		struct page *locked_page = NULL;
  		if (off == 0) {
  			lock_page(page);
  			locked_page = page;
  		}
  		err = ceph_uninline_data(vma->vm_file, locked_page);
  		if (locked_page)
  			unlock_page(locked_page);
  		if (err < 0)
  			goto out_free;
  	}
  
  	if (off + PAGE_SIZE <= size)
  		len = PAGE_SIZE;
  	else
  		len = size & ~PAGE_MASK;
  
  	dout("page_mkwrite %p %llx.%llx %llu~%zd getting caps i_size %llu\n",
  	     inode, ceph_vinop(inode), off, len, size);
  	if (fi->fmode & CEPH_FILE_MODE_LAZY)
  		want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
  	else
  		want = CEPH_CAP_FILE_BUFFER;
  
  	got = 0;
  	err = ceph_get_caps(vma->vm_file, CEPH_CAP_FILE_WR, want, off + len,
  			    &got, NULL);
  	if (err < 0)
  		goto out_free;
  
  	dout("page_mkwrite %p %llu~%zd got cap refs on %s\n",
  	     inode, off, len, ceph_cap_string(got));
  
  	/* Update time before taking page lock */
  	file_update_time(vma->vm_file);
  	inode_inc_iversion_raw(inode);
  
  	do {
  		struct ceph_snap_context *snapc;
  
  		lock_page(page);
  
  		if (page_mkwrite_check_truncate(page, inode) < 0) {
  			unlock_page(page);
  			ret = VM_FAULT_NOPAGE;
  			break;
  		}
  
  		snapc = ceph_find_incompatible(page);
  		if (!snapc) {
  			/* success.  we'll keep the page locked. */
  			set_page_dirty(page);
  			ret = VM_FAULT_LOCKED;
  			break;
  		}
  
  		unlock_page(page);
  
  		if (IS_ERR(snapc)) {
  			ret = VM_FAULT_SIGBUS;
  			break;
  		}
  
  		ceph_queue_writeback(inode);
  		err = wait_event_killable(ci->i_cap_wq,
  				context_is_writeable_or_written(inode, snapc));
  		ceph_put_snap_context(snapc);
  	} while (err == 0);
  
  	if (ret == VM_FAULT_LOCKED ||
  	    ci->i_inline_version != CEPH_INLINE_NONE) {
  		int dirty;
  		spin_lock(&ci->i_ceph_lock);
  		ci->i_inline_version = CEPH_INLINE_NONE;
  		dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR,
  					       &prealloc_cf);
  		spin_unlock(&ci->i_ceph_lock);
  		if (dirty)
  			__mark_inode_dirty(inode, dirty);
  	}
  
  	dout("page_mkwrite %p %llu~%zd dropping cap refs on %s ret %x\n",
  	     inode, off, len, ceph_cap_string(got), ret);
  	ceph_put_cap_refs(ci, got);
  out_free:
  	ceph_restore_sigs(&oldset);
  	sb_end_pagefault(inode->i_sb);
  	ceph_free_cap_flush(prealloc_cf);
  	if (err < 0)
  		ret = vmf_error(err);
  	return ret;
  }
  
  void ceph_fill_inline_data(struct inode *inode, struct page *locked_page,
  			   char	*data, size_t len)
  {
  	struct address_space *mapping = inode->i_mapping;
  	struct page *page;
  
  	if (locked_page) {
  		page = locked_page;
  	} else {
  		if (i_size_read(inode) == 0)
  			return;
  		page = find_or_create_page(mapping, 0,
  					   mapping_gfp_constraint(mapping,
  					   ~__GFP_FS));
  		if (!page)
  			return;
  		if (PageUptodate(page)) {
  			unlock_page(page);
  			put_page(page);
  			return;
  		}
  	}
  
  	dout("fill_inline_data %p %llx.%llx len %zu locked_page %p\n",
  	     inode, ceph_vinop(inode), len, locked_page);
  
  	if (len > 0) {
  		void *kaddr = kmap_atomic(page);
  		memcpy(kaddr, data, len);
  		kunmap_atomic(kaddr);
  	}
  
  	if (page != locked_page) {
  		if (len < PAGE_SIZE)
  			zero_user_segment(page, len, PAGE_SIZE);
  		else
  			flush_dcache_page(page);
  
  		SetPageUptodate(page);
  		unlock_page(page);
  		put_page(page);
  	}
  }
  
  int ceph_uninline_data(struct file *filp, struct page *locked_page)
  {
  	struct inode *inode = file_inode(filp);
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	struct ceph_osd_request *req;
  	struct page *page = NULL;
  	u64 len, inline_version;
  	int err = 0;
  	bool from_pagecache = false;
  
  	spin_lock(&ci->i_ceph_lock);
  	inline_version = ci->i_inline_version;
  	spin_unlock(&ci->i_ceph_lock);
  
  	dout("uninline_data %p %llx.%llx inline_version %llu\n",
  	     inode, ceph_vinop(inode), inline_version);
  
  	if (inline_version == 1 || /* initial version, no data */
  	    inline_version == CEPH_INLINE_NONE)
  		goto out;
  
  	if (locked_page) {
  		page = locked_page;
  		WARN_ON(!PageUptodate(page));
  	} else if (ceph_caps_issued(ci) &
  		   (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) {
  		page = find_get_page(inode->i_mapping, 0);
  		if (page) {
  			if (PageUptodate(page)) {
  				from_pagecache = true;
  				lock_page(page);
  			} else {
  				put_page(page);
  				page = NULL;
  			}
  		}
  	}
  
  	if (page) {
  		len = i_size_read(inode);
  		if (len > PAGE_SIZE)
  			len = PAGE_SIZE;
  	} else {
  		page = __page_cache_alloc(GFP_NOFS);
  		if (!page) {
  			err = -ENOMEM;
  			goto out;
  		}
  		err = __ceph_do_getattr(inode, page,
  					CEPH_STAT_CAP_INLINE_DATA, true);
  		if (err < 0) {
  			/* no inline data */
  			if (err == -ENODATA)
  				err = 0;
  			goto out;
  		}
  		len = err;
  	}
  
  	req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
  				    ceph_vino(inode), 0, &len, 0, 1,
  				    CEPH_OSD_OP_CREATE, CEPH_OSD_FLAG_WRITE,
  				    NULL, 0, 0, false);
  	if (IS_ERR(req)) {
  		err = PTR_ERR(req);
  		goto out;
  	}
  
  	req->r_mtime = inode->i_mtime;
  	err = ceph_osdc_start_request(&fsc->client->osdc, req, false);
  	if (!err)
  		err = ceph_osdc_wait_request(&fsc->client->osdc, req);
  	ceph_osdc_put_request(req);
  	if (err < 0)
  		goto out;
  
  	req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
  				    ceph_vino(inode), 0, &len, 1, 3,
  				    CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
  				    NULL, ci->i_truncate_seq,
  				    ci->i_truncate_size, false);
  	if (IS_ERR(req)) {
  		err = PTR_ERR(req);
  		goto out;
  	}
  
  	osd_req_op_extent_osd_data_pages(req, 1, &page, len, 0, false, false);
  
  	{
  		__le64 xattr_buf = cpu_to_le64(inline_version);
  		err = osd_req_op_xattr_init(req, 0, CEPH_OSD_OP_CMPXATTR,
  					    "inline_version", &xattr_buf,
  					    sizeof(xattr_buf),
  					    CEPH_OSD_CMPXATTR_OP_GT,
  					    CEPH_OSD_CMPXATTR_MODE_U64);
  		if (err)
  			goto out_put;
  	}
  
  	{
  		char xattr_buf[32];
  		int xattr_len = snprintf(xattr_buf, sizeof(xattr_buf),
  					 "%llu", inline_version);
  		err = osd_req_op_xattr_init(req, 2, CEPH_OSD_OP_SETXATTR,
  					    "inline_version",
  					    xattr_buf, xattr_len, 0, 0);
  		if (err)
  			goto out_put;
  	}
  
  	req->r_mtime = inode->i_mtime;
  	err = ceph_osdc_start_request(&fsc->client->osdc, req, false);
  	if (!err)
  		err = ceph_osdc_wait_request(&fsc->client->osdc, req);
  
  	ceph_update_write_latency(&fsc->mdsc->metric, req->r_start_latency,
  				  req->r_end_latency, err);
  
  out_put:
  	ceph_osdc_put_request(req);
  	if (err == -ECANCELED)
  		err = 0;
  out:
  	if (page && page != locked_page) {
  		if (from_pagecache) {
  			unlock_page(page);
  			put_page(page);
  		} else
  			__free_pages(page, 0);
  	}
  
  	dout("uninline_data %p %llx.%llx inline_version %llu = %d\n",
  	     inode, ceph_vinop(inode), inline_version, err);
  	return err;
  }
  
  static const struct vm_operations_struct ceph_vmops = {
  	.fault		= ceph_filemap_fault,
  	.page_mkwrite	= ceph_page_mkwrite,
  };
  
  int ceph_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	struct address_space *mapping = file->f_mapping;
  
  	if (!mapping->a_ops->readpage)
  		return -ENOEXEC;
  	file_accessed(file);
  	vma->vm_ops = &ceph_vmops;
  	return 0;
  }
  
  enum {
  	POOL_READ	= 1,
  	POOL_WRITE	= 2,
  };
  
  static int __ceph_pool_perm_get(struct ceph_inode_info *ci,
  				s64 pool, struct ceph_string *pool_ns)
  {
  	struct ceph_fs_client *fsc = ceph_inode_to_client(&ci->vfs_inode);
  	struct ceph_mds_client *mdsc = fsc->mdsc;
  	struct ceph_osd_request *rd_req = NULL, *wr_req = NULL;
  	struct rb_node **p, *parent;
  	struct ceph_pool_perm *perm;
  	struct page **pages;
  	size_t pool_ns_len;
  	int err = 0, err2 = 0, have = 0;
  
  	down_read(&mdsc->pool_perm_rwsem);
  	p = &mdsc->pool_perm_tree.rb_node;
  	while (*p) {
  		perm = rb_entry(*p, struct ceph_pool_perm, node);
  		if (pool < perm->pool)
  			p = &(*p)->rb_left;
  		else if (pool > perm->pool)
  			p = &(*p)->rb_right;
  		else {
  			int ret = ceph_compare_string(pool_ns,
  						perm->pool_ns,
  						perm->pool_ns_len);
  			if (ret < 0)
  				p = &(*p)->rb_left;
  			else if (ret > 0)
  				p = &(*p)->rb_right;
  			else {
  				have = perm->perm;
  				break;
  			}
  		}
  	}
  	up_read(&mdsc->pool_perm_rwsem);
  	if (*p)
  		goto out;
  
  	if (pool_ns)
  		dout("__ceph_pool_perm_get pool %lld ns %.*s no perm cached\n",
  		     pool, (int)pool_ns->len, pool_ns->str);
  	else
  		dout("__ceph_pool_perm_get pool %lld no perm cached\n", pool);
  
  	down_write(&mdsc->pool_perm_rwsem);
  	p = &mdsc->pool_perm_tree.rb_node;
  	parent = NULL;
  	while (*p) {
  		parent = *p;
  		perm = rb_entry(parent, struct ceph_pool_perm, node);
  		if (pool < perm->pool)
  			p = &(*p)->rb_left;
  		else if (pool > perm->pool)
  			p = &(*p)->rb_right;
  		else {
  			int ret = ceph_compare_string(pool_ns,
  						perm->pool_ns,
  						perm->pool_ns_len);
  			if (ret < 0)
  				p = &(*p)->rb_left;
  			else if (ret > 0)
  				p = &(*p)->rb_right;
  			else {
  				have = perm->perm;
  				break;
  			}
  		}
  	}
  	if (*p) {
  		up_write(&mdsc->pool_perm_rwsem);
  		goto out;
  	}
  
  	rd_req = ceph_osdc_alloc_request(&fsc->client->osdc, NULL,
  					 1, false, GFP_NOFS);
  	if (!rd_req) {
  		err = -ENOMEM;
  		goto out_unlock;
  	}
  
  	rd_req->r_flags = CEPH_OSD_FLAG_READ;
  	osd_req_op_init(rd_req, 0, CEPH_OSD_OP_STAT, 0);
  	rd_req->r_base_oloc.pool = pool;
  	if (pool_ns)
  		rd_req->r_base_oloc.pool_ns = ceph_get_string(pool_ns);
  	ceph_oid_printf(&rd_req->r_base_oid, "%llx.00000000", ci->i_vino.ino);
  
  	err = ceph_osdc_alloc_messages(rd_req, GFP_NOFS);
  	if (err)
  		goto out_unlock;
  
  	wr_req = ceph_osdc_alloc_request(&fsc->client->osdc, NULL,
  					 1, false, GFP_NOFS);
  	if (!wr_req) {
  		err = -ENOMEM;
  		goto out_unlock;
  	}
  
  	wr_req->r_flags = CEPH_OSD_FLAG_WRITE;
  	osd_req_op_init(wr_req, 0, CEPH_OSD_OP_CREATE, CEPH_OSD_OP_FLAG_EXCL);
  	ceph_oloc_copy(&wr_req->r_base_oloc, &rd_req->r_base_oloc);
  	ceph_oid_copy(&wr_req->r_base_oid, &rd_req->r_base_oid);
  
  	err = ceph_osdc_alloc_messages(wr_req, GFP_NOFS);
  	if (err)
  		goto out_unlock;
  
  	/* one page should be large enough for STAT data */
  	pages = ceph_alloc_page_vector(1, GFP_KERNEL);
  	if (IS_ERR(pages)) {
  		err = PTR_ERR(pages);
  		goto out_unlock;
  	}
  
  	osd_req_op_raw_data_in_pages(rd_req, 0, pages, PAGE_SIZE,
  				     0, false, true);
  	err = ceph_osdc_start_request(&fsc->client->osdc, rd_req, false);
  
  	wr_req->r_mtime = ci->vfs_inode.i_mtime;
  	err2 = ceph_osdc_start_request(&fsc->client->osdc, wr_req, false);
  
  	if (!err)
  		err = ceph_osdc_wait_request(&fsc->client->osdc, rd_req);
  	if (!err2)
  		err2 = ceph_osdc_wait_request(&fsc->client->osdc, wr_req);
  
  	if (err >= 0 || err == -ENOENT)
  		have |= POOL_READ;
  	else if (err != -EPERM) {
  		if (err == -EBLOCKLISTED)
  			fsc->blocklisted = true;
  		goto out_unlock;
  	}
  
  	if (err2 == 0 || err2 == -EEXIST)
  		have |= POOL_WRITE;
  	else if (err2 != -EPERM) {
  		if (err2 == -EBLOCKLISTED)
  			fsc->blocklisted = true;
  		err = err2;
  		goto out_unlock;
  	}
  
  	pool_ns_len = pool_ns ? pool_ns->len : 0;
  	perm = kmalloc(sizeof(*perm) + pool_ns_len + 1, GFP_NOFS);
  	if (!perm) {
  		err = -ENOMEM;
  		goto out_unlock;
  	}
  
  	perm->pool = pool;
  	perm->perm = have;
  	perm->pool_ns_len = pool_ns_len;
  	if (pool_ns_len > 0)
  		memcpy(perm->pool_ns, pool_ns->str, pool_ns_len);
  	perm->pool_ns[pool_ns_len] = 0;
  
  	rb_link_node(&perm->node, parent, p);
  	rb_insert_color(&perm->node, &mdsc->pool_perm_tree);
  	err = 0;
  out_unlock:
  	up_write(&mdsc->pool_perm_rwsem);
  
  	ceph_osdc_put_request(rd_req);
  	ceph_osdc_put_request(wr_req);
  out:
  	if (!err)
  		err = have;
  	if (pool_ns)
  		dout("__ceph_pool_perm_get pool %lld ns %.*s result = %d\n",
  		     pool, (int)pool_ns->len, pool_ns->str, err);
  	else
  		dout("__ceph_pool_perm_get pool %lld result = %d\n", pool, err);
  	return err;
  }
  
  int ceph_pool_perm_check(struct inode *inode, int need)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_string *pool_ns;
  	s64 pool;
  	int ret, flags;
  
  	if (ci->i_vino.snap != CEPH_NOSNAP) {
  		/*
  		 * Pool permission check needs to write to the first object.
  		 * But for snapshot, head of the first object may have alread
  		 * been deleted. Skip check to avoid creating orphan object.
  		 */
  		return 0;
  	}
  
  	if (ceph_test_mount_opt(ceph_inode_to_client(inode),
  				NOPOOLPERM))
  		return 0;
  
  	spin_lock(&ci->i_ceph_lock);
  	flags = ci->i_ceph_flags;
  	pool = ci->i_layout.pool_id;
  	spin_unlock(&ci->i_ceph_lock);
  check:
  	if (flags & CEPH_I_POOL_PERM) {
  		if ((need & CEPH_CAP_FILE_RD) && !(flags & CEPH_I_POOL_RD)) {
  			dout("ceph_pool_perm_check pool %lld no read perm\n",
  			     pool);
  			return -EPERM;
  		}
  		if ((need & CEPH_CAP_FILE_WR) && !(flags & CEPH_I_POOL_WR)) {
  			dout("ceph_pool_perm_check pool %lld no write perm\n",
  			     pool);
  			return -EPERM;
  		}
  		return 0;
  	}
  
  	pool_ns = ceph_try_get_string(ci->i_layout.pool_ns);
  	ret = __ceph_pool_perm_get(ci, pool, pool_ns);
  	ceph_put_string(pool_ns);
  	if (ret < 0)
  		return ret;
  
  	flags = CEPH_I_POOL_PERM;
  	if (ret & POOL_READ)
  		flags |= CEPH_I_POOL_RD;
  	if (ret & POOL_WRITE)
  		flags |= CEPH_I_POOL_WR;
  
  	spin_lock(&ci->i_ceph_lock);
  	if (pool == ci->i_layout.pool_id &&
  	    pool_ns == rcu_dereference_raw(ci->i_layout.pool_ns)) {
  		ci->i_ceph_flags |= flags;
          } else {
  		pool = ci->i_layout.pool_id;
  		flags = ci->i_ceph_flags;
  	}
  	spin_unlock(&ci->i_ceph_lock);
  	goto check;
  }
  
  void ceph_pool_perm_destroy(struct ceph_mds_client *mdsc)
  {
  	struct ceph_pool_perm *perm;
  	struct rb_node *n;
  
  	while (!RB_EMPTY_ROOT(&mdsc->pool_perm_tree)) {
  		n = rb_first(&mdsc->pool_perm_tree);
  		perm = rb_entry(n, struct ceph_pool_perm, node);
  		rb_erase(n, &mdsc->pool_perm_tree);
  		kfree(perm);
  	}
  }
  