text: #include "ceph_debug.h"
  
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/file.h>
  #include <linux/namei.h>
  #include <linux/writeback.h>
  
  #include "super.h"
  #include "mds_client.h"
  
  /*
   * Ceph file operations
   *
   * Implement basic open/close functionality, and implement
   * read/write.
   *
   * We implement three modes of file I/O:
   *  - buffered uses the generic_file_aio_{read,write} helpers
   *
   *  - synchronous is used when there is multi-client read/write
   *    sharing, avoids the page cache, and synchronously waits for an
   *    ack from the OSD.
   *
   *  - direct io takes the variant of the sync path that references
   *    user pages directly.
   *
   * fsync() flushes and waits on dirty pages, but just queues metadata
   * for writeback: since the MDS can recover size and mtime there is no
   * need to wait for MDS acknowledgement.
   */
  
  
  /*
   * Prepare an open request.  Preallocate ceph_cap to avoid an
   * inopportune ENOMEM later.
   */
  static struct ceph_mds_request *
  prepare_open_request(struct super_block *sb, int flags, int create_mode)
  {
  	struct ceph_client *client = ceph_sb_to_client(sb);
  	struct ceph_mds_client *mdsc = &client->mdsc;
  	struct ceph_mds_request *req;
  	int want_auth = USE_ANY_MDS;
  	int op = (flags & O_CREAT) ? CEPH_MDS_OP_CREATE : CEPH_MDS_OP_OPEN;
  
  	if (flags & (O_WRONLY|O_RDWR|O_CREAT|O_TRUNC))
  		want_auth = USE_AUTH_MDS;
  
  	req = ceph_mdsc_create_request(mdsc, op, want_auth);
  	if (IS_ERR(req))
  		goto out;
  	req->r_fmode = ceph_flags_to_mode(flags);
  	req->r_args.open.flags = cpu_to_le32(flags);
  	req->r_args.open.mode = cpu_to_le32(create_mode);
  	req->r_args.open.preferred = cpu_to_le32(-1);
  out:
  	return req;
  }
  
  /*
   * initialize private struct file data.
   * if we fail, clean up by dropping fmode reference on the ceph_inode
   */
  static int ceph_init_file(struct inode *inode, struct file *file, int fmode)
  {
  	struct ceph_file_info *cf;
  	int ret = 0;
  
  	switch (inode->i_mode & S_IFMT) {
  	case S_IFREG:
  	case S_IFDIR:
  		dout("init_file %p %p 0%o (regular)\n", inode, file,
  		     inode->i_mode);
  		cf = kmem_cache_alloc(ceph_file_cachep, GFP_NOFS | __GFP_ZERO);
  		if (cf == NULL) {
  			ceph_put_fmode(ceph_inode(inode), fmode); /* clean up */
  			return -ENOMEM;
  		}
  		cf->fmode = fmode;
  		cf->next_offset = 2;
  		file->private_data = cf;
  		BUG_ON(inode->i_fop->release != ceph_release);
  		break;
  
  	case S_IFLNK:
  		dout("init_file %p %p 0%o (symlink)\n", inode, file,
  		     inode->i_mode);
  		ceph_put_fmode(ceph_inode(inode), fmode); /* clean up */
  		break;
  
  	default:
  		dout("init_file %p %p 0%o (special)\n", inode, file,
  		     inode->i_mode);
  		/*
  		 * we need to drop the open ref now, since we don't
  		 * have .release set to ceph_release.
  		 */
  		ceph_put_fmode(ceph_inode(inode), fmode); /* clean up */
  		BUG_ON(inode->i_fop->release == ceph_release);
  
  		/* call the proper open fop */
  		ret = inode->i_fop->open(inode, file);
  	}
  	return ret;
  }
  
  /*
   * If the filp already has private_data, that means the file was
   * already opened by intent during lookup, and we do nothing.
   *
   * If we already have the requisite capabilities, we can satisfy
   * the open request locally (no need to request new caps from the
   * MDS).  We do, however, need to inform the MDS (asynchronously)
   * if our wanted caps set expands.
   */
  int ceph_open(struct inode *inode, struct file *file)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_client *client = ceph_sb_to_client(inode->i_sb);
  	struct ceph_mds_client *mdsc = &client->mdsc;
  	struct ceph_mds_request *req;
  	struct ceph_file_info *cf = file->private_data;
  	struct inode *parent_inode = file->f_dentry->d_parent->d_inode;
  	int err;
  	int flags, fmode, wanted;
  
  	if (cf) {
  		dout("open file %p is already opened\n", file);
  		return 0;
  	}
  
  	/* filter out O_CREAT|O_EXCL; vfs did that already.  yuck. */
  	flags = file->f_flags & ~(O_CREAT|O_EXCL);
  	if (S_ISDIR(inode->i_mode))
  		flags = O_DIRECTORY;  /* mds likes to know */
  
  	dout("open inode %p ino %llx.%llx file %p flags %d (%d)\n", inode,
  	     ceph_vinop(inode), file, flags, file->f_flags);
  	fmode = ceph_flags_to_mode(flags);
  	wanted = ceph_caps_for_mode(fmode);
  
  	/* snapped files are read-only */
  	if (ceph_snap(inode) != CEPH_NOSNAP && (file->f_mode & FMODE_WRITE))
  		return -EROFS;
  
  	/* trivially open snapdir */
  	if (ceph_snap(inode) == CEPH_SNAPDIR) {
  		spin_lock(&inode->i_lock);
  		__ceph_get_fmode(ci, fmode);
  		spin_unlock(&inode->i_lock);
  		return ceph_init_file(inode, file, fmode);
  	}
  
  	/*
  	 * No need to block if we have any caps.  Update wanted set
  	 * asynchronously.
  	 */
  	spin_lock(&inode->i_lock);
  	if (__ceph_is_any_real_caps(ci)) {
  		int mds_wanted = __ceph_caps_mds_wanted(ci);
  		int issued = __ceph_caps_issued(ci, NULL);
  
  		dout("open %p fmode %d want %s issued %s using existing\n",
  		     inode, fmode, ceph_cap_string(wanted),
  		     ceph_cap_string(issued));
  		__ceph_get_fmode(ci, fmode);
  		spin_unlock(&inode->i_lock);
  
  		/* adjust wanted? */
  		if ((issued & wanted) != wanted &&
  		    (mds_wanted & wanted) != wanted &&
  		    ceph_snap(inode) != CEPH_SNAPDIR)
  			ceph_check_caps(ci, 0, NULL);
  
  		return ceph_init_file(inode, file, fmode);
  	} else if (ceph_snap(inode) != CEPH_NOSNAP &&
  		   (ci->i_snap_caps & wanted) == wanted) {
  		__ceph_get_fmode(ci, fmode);
  		spin_unlock(&inode->i_lock);
  		return ceph_init_file(inode, file, fmode);
  	}
  	spin_unlock(&inode->i_lock);
  
  	dout("open fmode %d wants %s\n", fmode, ceph_cap_string(wanted));
  	req = prepare_open_request(inode->i_sb, flags, 0);
  	if (IS_ERR(req)) {
  		err = PTR_ERR(req);
  		goto out;
  	}
  	req->r_inode = igrab(inode);
  	req->r_num_caps = 1;
  	err = ceph_mdsc_do_request(mdsc, parent_inode, req);
  	if (!err)
  		err = ceph_init_file(inode, file, req->r_fmode);
  	ceph_mdsc_put_request(req);
  	dout("open result=%d on %llx.%llx\n", err, ceph_vinop(inode));
  out:
  	return err;
  }
  
  
  /*
   * Do a lookup + open with a single request.
   *
   * If this succeeds, but some subsequent check in the vfs
   * may_open() fails, the struct *file gets cleaned up (i.e.
   * ceph_release gets called).  So fear not!
   */
  /*
   * flags
   *  path_lookup_open   -> LOOKUP_OPEN
   *  path_lookup_create -> LOOKUP_OPEN|LOOKUP_CREATE
   */
  struct dentry *ceph_lookup_open(struct inode *dir, struct dentry *dentry,
  				struct nameidata *nd, int mode,
  				int locked_dir)
  {
  	struct ceph_client *client = ceph_sb_to_client(dir->i_sb);
  	struct ceph_mds_client *mdsc = &client->mdsc;
  	struct file *file = nd->intent.open.file;
  	struct inode *parent_inode = get_dentry_parent_inode(file->f_dentry);
  	struct ceph_mds_request *req;
  	int err;
  	int flags = nd->intent.open.flags - 1;  /* silly vfs! */
  
  	dout("ceph_lookup_open dentry %p '%.*s' flags %d mode 0%o\n",
  	     dentry, dentry->d_name.len, dentry->d_name.name, flags, mode);
  
  	/* do the open */
  	req = prepare_open_request(dir->i_sb, flags, mode);
  	if (IS_ERR(req))
  		return ERR_CAST(req);
  	req->r_dentry = dget(dentry);
  	req->r_num_caps = 2;
  	if (flags & O_CREAT) {
  		req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
  		req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
  	}
  	req->r_locked_dir = dir;           /* caller holds dir->i_mutex */
  	err = ceph_mdsc_do_request(mdsc, parent_inode, req);
  	dentry = ceph_finish_lookup(req, dentry, err);
  	if (!err && (flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
  		err = ceph_handle_notrace_create(dir, dentry);
  	if (!err)
  		err = ceph_init_file(req->r_dentry->d_inode, file,
  				     req->r_fmode);
  	ceph_mdsc_put_request(req);
  	dout("ceph_lookup_open result=%p\n", dentry);
  	return dentry;
  }
  
  int ceph_release(struct inode *inode, struct file *file)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_file_info *cf = file->private_data;
  
  	dout("release inode %p file %p\n", inode, file);
  	ceph_put_fmode(ci, cf->fmode);
  	if (cf->last_readdir)
  		ceph_mdsc_put_request(cf->last_readdir);
  	kfree(cf->last_name);
  	kfree(cf->dir_info);
  	dput(cf->dentry);
  	kmem_cache_free(ceph_file_cachep, cf);
  
  	/* wake up anyone waiting for caps on this inode */
  	wake_up_all(&ci->i_cap_wq);
  	return 0;
  }
  
  /*
   * build a vector of user pages
   */
  static struct page **get_direct_page_vector(const char __user *data,
  					    int num_pages,
  					    loff_t off, size_t len)
  {
  	struct page **pages;
  	int rc;
  
  	pages = kmalloc(sizeof(*pages) * num_pages, GFP_NOFS);
  	if (!pages)
  		return ERR_PTR(-ENOMEM);
  
  	down_read(&current->mm->mmap_sem);
  	rc = get_user_pages(current, current->mm, (unsigned long)data,
  			    num_pages, 0, 0, pages, NULL);
  	up_read(&current->mm->mmap_sem);
  	if (rc < 0)
  		goto fail;
  	return pages;
  
  fail:
  	kfree(pages);
  	return ERR_PTR(rc);
  }
  
  static void put_page_vector(struct page **pages, int num_pages)
  {
  	int i;
  
  	for (i = 0; i < num_pages; i++)
  		put_page(pages[i]);
  	kfree(pages);
  }
  
  void ceph_release_page_vector(struct page **pages, int num_pages)
  {
  	int i;
  
  	for (i = 0; i < num_pages; i++)
  		__free_pages(pages[i], 0);
  	kfree(pages);
  }
  
  /*
   * allocate a vector new pages
   */
  static struct page **ceph_alloc_page_vector(int num_pages, gfp_t flags)
  {
  	struct page **pages;
  	int i;
  
  	pages = kmalloc(sizeof(*pages) * num_pages, flags);
  	if (!pages)
  		return ERR_PTR(-ENOMEM);
  	for (i = 0; i < num_pages; i++) {
  		pages[i] = __page_cache_alloc(flags);
  		if (pages[i] == NULL) {
  			ceph_release_page_vector(pages, i);
  			return ERR_PTR(-ENOMEM);
  		}
  	}
  	return pages;
  }
  
  /*
   * copy user data into a page vector
   */
  static int copy_user_to_page_vector(struct page **pages,
  				    const char __user *data,
  				    loff_t off, size_t len)
  {
  	int i = 0;
  	int po = off & ~PAGE_CACHE_MASK;
  	int left = len;
  	int l, bad;
  
  	while (left > 0) {
  		l = min_t(int, PAGE_CACHE_SIZE-po, left);
  		bad = copy_from_user(page_address(pages[i]) + po, data, l);
  		if (bad == l)
  			return -EFAULT;
  		data += l - bad;
  		left -= l - bad;
  		po += l - bad;
  		if (po == PAGE_CACHE_SIZE) {
  			po = 0;
  			i++;
  		}
  	}
  	return len;
  }
  
  /*
   * copy user data from a page vector into a user pointer
   */
  static int copy_page_vector_to_user(struct page **pages, char __user *data,
  				    loff_t off, size_t len)
  {
  	int i = 0;
  	int po = off & ~PAGE_CACHE_MASK;
  	int left = len;
  	int l, bad;
  
  	while (left > 0) {
  		l = min_t(int, left, PAGE_CACHE_SIZE-po);
  		bad = copy_to_user(data, page_address(pages[i]) + po, l);
  		if (bad == l)
  			return -EFAULT;
  		data += l - bad;
  		left -= l - bad;
  		if (po) {
  			po += l - bad;
  			if (po == PAGE_CACHE_SIZE)
  				po = 0;
  		}
  		i++;
  	}
  	return len;
  }
  
  /*
   * Zero an extent within a page vector.  Offset is relative to the
   * start of the first page.
   */
  static void zero_page_vector_range(int off, int len, struct page **pages)
  {
  	int i = off >> PAGE_CACHE_SHIFT;
  
  	off &= ~PAGE_CACHE_MASK;
  
  	dout("zero_page_vector_page %u~%u\n", off, len);
  
  	/* leading partial page? */
  	if (off) {
  		int end = min((int)PAGE_CACHE_SIZE, off + len);
  		dout("zeroing %d %p head from %d\n", i, pages[i],
  		     (int)off);
  		zero_user_segment(pages[i], off, end);
  		len -= (end - off);
  		i++;
  	}
  	while (len >= PAGE_CACHE_SIZE) {
  		dout("zeroing %d %p len=%d\n", i, pages[i], len);
  		zero_user_segment(pages[i], 0, PAGE_CACHE_SIZE);
  		len -= PAGE_CACHE_SIZE;
  		i++;
  	}
  	/* trailing partial page? */
  	if (len) {
  		dout("zeroing %d %p tail to %d\n", i, pages[i], (int)len);
  		zero_user_segment(pages[i], 0, len);
  	}
  }
  
  
  /*
   * Read a range of bytes striped over one or more objects.  Iterate over
   * objects we stripe over.  (That's not atomic, but good enough for now.)
   *
   * If we get a short result from the OSD, check against i_size; we need to
   * only return a short read to the caller if we hit EOF.
   */
  static int striped_read(struct inode *inode,
  			u64 off, u64 len,
  			struct page **pages, int num_pages,
  			int *checkeof)
  {
  	struct ceph_client *client = ceph_inode_to_client(inode);
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	u64 pos, this_len;
  	int page_off = off & ~PAGE_CACHE_MASK; /* first byte's offset in page */
  	int left, pages_left;
  	int read;
  	struct page **page_pos;
  	int ret;
  	bool hit_stripe, was_short;
  
  	/*
  	 * we may need to do multiple reads.  not atomic, unfortunately.
  	 */
  	pos = off;
  	left = len;
  	page_pos = pages;
  	pages_left = num_pages;
  	read = 0;
  
  more:
  	this_len = left;
  	ret = ceph_osdc_readpages(&client->osdc, ceph_vino(inode),
  				  &ci->i_layout, pos, &this_len,
  				  ci->i_truncate_seq,
  				  ci->i_truncate_size,
  				  page_pos, pages_left);
  	hit_stripe = this_len < left;
  	was_short = ret >= 0 && ret < this_len;
  	if (ret == -ENOENT)
  		ret = 0;
  	dout("striped_read %llu~%u (read %u) got %d%s%s\n", pos, left, read,
  	     ret, hit_stripe ? " HITSTRIPE" : "", was_short ? " SHORT" : "");
  
  	if (ret > 0) {
  		int didpages =
  			((pos & ~PAGE_CACHE_MASK) + ret) >> PAGE_CACHE_SHIFT;
  
  		if (read < pos - off) {
  			dout(" zero gap %llu to %llu\n", off + read, pos);
  			zero_page_vector_range(page_off + read,
  					       pos - off - read, pages);
  		}
  		pos += ret;
  		read = pos - off;
  		left -= ret;
  		page_pos += didpages;
  		pages_left -= didpages;
  
  		/* hit stripe? */
  		if (left && hit_stripe)
  			goto more;
  	}
  
  	if (was_short) {
  		/* was original extent fully inside i_size? */
  		if (pos + left <= inode->i_size) {
  			dout("zero tail\n");
  			zero_page_vector_range(page_off + read, len - read,
  					       pages);
  			read = len;
  			goto out;
  		}
  
  		/* check i_size */
  		*checkeof = 1;
  	}
  
  out:
  	if (ret >= 0)
  		ret = read;
  	dout("striped_read returns %d\n", ret);
  	return ret;
  }
  
  /*
   * Completely synchronous read and write methods.  Direct from __user
   * buffer to osd, or directly to user pages (if O_DIRECT).
   *
   * If the read spans object boundary, just do multiple reads.
   */
  static ssize_t ceph_sync_read(struct file *file, char __user *data,
  			      unsigned len, loff_t *poff, int *checkeof)
  {
  	struct inode *inode = file->f_dentry->d_inode;
  	struct page **pages;
  	u64 off = *poff;
  	int num_pages = calc_pages_for(off, len);
  	int ret;
  
  	dout("sync_read on file %p %llu~%u %s\n", file, off, len,
  	     (file->f_flags & O_DIRECT) ? "O_DIRECT" : "");
  
  	if (file->f_flags & O_DIRECT) {
  		pages = get_direct_page_vector(data, num_pages, off, len);
  
  		/*
  		 * flush any page cache pages in this range.  this
  		 * will make concurrent normal and O_DIRECT io slow,
  		 * but it will at least behave sensibly when they are
  		 * in sequence.
  		 */
  	} else {
  		pages = ceph_alloc_page_vector(num_pages, GFP_NOFS);
  	}
  	if (IS_ERR(pages))
  		return PTR_ERR(pages);
  
  	ret = filemap_write_and_wait(inode->i_mapping);
  	if (ret < 0)
  		goto done;
  
  	ret = striped_read(inode, off, len, pages, num_pages, checkeof);
  
  	if (ret >= 0 && (file->f_flags & O_DIRECT) == 0)
  		ret = copy_page_vector_to_user(pages, data, off, ret);
  	if (ret >= 0)
  		*poff = off + ret;
  
  done:
  	if (file->f_flags & O_DIRECT)
  		put_page_vector(pages, num_pages);
  	else
  		ceph_release_page_vector(pages, num_pages);
  	dout("sync_read result %d\n", ret);
  	return ret;
  }
  
  /*
   * Write commit callback, called if we requested both an ACK and
   * ONDISK commit reply from the OSD.
   */
  static void sync_write_commit(struct ceph_osd_request *req,
  			      struct ceph_msg *msg)
  {
  	struct ceph_inode_info *ci = ceph_inode(req->r_inode);
  
  	dout("sync_write_commit %p tid %llu\n", req, req->r_tid);
  	spin_lock(&ci->i_unsafe_lock);
  	list_del_init(&req->r_unsafe_item);
  	spin_unlock(&ci->i_unsafe_lock);
  	ceph_put_cap_refs(ci, CEPH_CAP_FILE_WR);
  }
  
  /*
   * Synchronous write, straight from __user pointer or user pages (if
   * O_DIRECT).
   *
   * If write spans object boundary, just do multiple writes.  (For a
   * correct atomic write, we should e.g. take write locks on all
   * objects, rollback on failure, etc.)
   */
  static ssize_t ceph_sync_write(struct file *file, const char __user *data,
  			       size_t left, loff_t *offset)
  {
  	struct inode *inode = file->f_dentry->d_inode;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_client *client = ceph_inode_to_client(inode);
  	struct ceph_osd_request *req;
  	struct page **pages;
  	int num_pages;
  	long long unsigned pos;
  	u64 len;
  	int written = 0;
  	int flags;
  	int do_sync = 0;
  	int check_caps = 0;
  	int ret;
  	struct timespec mtime = CURRENT_TIME;
  
  	if (ceph_snap(file->f_dentry->d_inode) != CEPH_NOSNAP)
  		return -EROFS;
  
  	dout("sync_write on file %p %lld~%u %s\n", file, *offset,
  	     (unsigned)left, (file->f_flags & O_DIRECT) ? "O_DIRECT" : "");
  
  	if (file->f_flags & O_APPEND)
  		pos = i_size_read(inode);
  	else
  		pos = *offset;
  
  	ret = filemap_write_and_wait_range(inode->i_mapping, pos, pos + left);
  	if (ret < 0)
  		return ret;
  
  	ret = invalidate_inode_pages2_range(inode->i_mapping,
  					    pos >> PAGE_CACHE_SHIFT,
  					    (pos + left) >> PAGE_CACHE_SHIFT);
  	if (ret < 0)
  		dout("invalidate_inode_pages2_range returned %d\n", ret);
  
  	flags = CEPH_OSD_FLAG_ORDERSNAP |
  		CEPH_OSD_FLAG_ONDISK |
  		CEPH_OSD_FLAG_WRITE;
  	if ((file->f_flags & (O_SYNC|O_DIRECT)) == 0)
  		flags |= CEPH_OSD_FLAG_ACK;
  	else
  		do_sync = 1;
  
  	/*
  	 * we may need to do multiple writes here if we span an object
  	 * boundary.  this isn't atomic, unfortunately.  :(
  	 */
  more:
  	len = left;
  	req = ceph_osdc_new_request(&client->osdc, &ci->i_layout,
  				    ceph_vino(inode), pos, &len,
  				    CEPH_OSD_OP_WRITE, flags,
  				    ci->i_snap_realm->cached_context,
  				    do_sync,
  				    ci->i_truncate_seq, ci->i_truncate_size,
  				    &mtime, false, 2);
  	if (!req)
  		return -ENOMEM;
  
  	num_pages = calc_pages_for(pos, len);
  
  	if (file->f_flags & O_DIRECT) {
  		pages = get_direct_page_vector(data, num_pages, pos, len);
  		if (IS_ERR(pages)) {
  			ret = PTR_ERR(pages);
  			goto out;
  		}
  
  		/*
  		 * throw out any page cache pages in this range. this
  		 * may block.
  		 */
  		truncate_inode_pages_range(inode->i_mapping, pos,
  					   (pos+len) | (PAGE_CACHE_SIZE-1));
  	} else {
  		pages = ceph_alloc_page_vector(num_pages, GFP_NOFS);
  		if (IS_ERR(pages)) {
  			ret = PTR_ERR(pages);
  			goto out;
  		}
  		ret = copy_user_to_page_vector(pages, data, pos, len);
  		if (ret < 0) {
  			ceph_release_page_vector(pages, num_pages);
  			goto out;
  		}
  
  		if ((file->f_flags & O_SYNC) == 0) {
  			/* get a second commit callback */
  			req->r_safe_callback = sync_write_commit;
  			req->r_own_pages = 1;
  		}
  	}
  	req->r_pages = pages;
  	req->r_num_pages = num_pages;
  	req->r_inode = inode;
  
  	ret = ceph_osdc_start_request(&client->osdc, req, false);
  	if (!ret) {
  		if (req->r_safe_callback) {
  			/*
  			 * Add to inode unsafe list only after we
  			 * start_request so that a tid has been assigned.
  			 */
  			spin_lock(&ci->i_unsafe_lock);
  			list_add(&req->r_unsafe_item, &ci->i_unsafe_writes);
  			spin_unlock(&ci->i_unsafe_lock);
  			ceph_get_cap_refs(ci, CEPH_CAP_FILE_WR);
  		}
  		ret = ceph_osdc_wait_request(&client->osdc, req);
  	}
  
  	if (file->f_flags & O_DIRECT)
  		put_page_vector(pages, num_pages);
  	else if (file->f_flags & O_SYNC)
  		ceph_release_page_vector(pages, num_pages);
  
  out:
  	ceph_osdc_put_request(req);
  	if (ret == 0) {
  		pos += len;
  		written += len;
  		left -= len;
  		if (left)
  			goto more;
  
  		ret = written;
  		*offset = pos;
  		if (pos > i_size_read(inode))
  			check_caps = ceph_inode_set_size(inode, pos);
  		if (check_caps)
  			ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY,
  					NULL);
  	}
  	return ret;
  }
  
  /*
   * Wrap generic_file_aio_read with checks for cap bits on the inode.
   * Atomically grab references, so that those bits are not released
   * back to the MDS mid-read.
   *
   * Hmm, the sync read case isn't actually async... should it be?
   */
  static ssize_t ceph_aio_read(struct kiocb *iocb, const struct iovec *iov,
  			     unsigned long nr_segs, loff_t pos)
  {
  	struct file *filp = iocb->ki_filp;
  	struct ceph_file_info *fi = filp->private_data;
  	loff_t *ppos = &iocb->ki_pos;
  	size_t len = iov->iov_len;
  	struct inode *inode = filp->f_dentry->d_inode;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	void __user *base = iov->iov_base;
  	ssize_t ret;
  	int want, got = 0;
  	int checkeof = 0, read = 0;
  
  	dout("aio_read %p %llx.%llx %llu~%u trying to get caps on %p\n",
  	     inode, ceph_vinop(inode), pos, (unsigned)len, inode);
  again:
  	__ceph_do_pending_vmtruncate(inode);
  	if (fi->fmode & CEPH_FILE_MODE_LAZY)
  		want = CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO;
  	else
  		want = CEPH_CAP_FILE_CACHE;
  	ret = ceph_get_caps(ci, CEPH_CAP_FILE_RD, want, &got, -1);
  	if (ret < 0)
  		goto out;
  	dout("aio_read %p %llx.%llx %llu~%u got cap refs on %s\n",
  	     inode, ceph_vinop(inode), pos, (unsigned)len,
  	     ceph_cap_string(got));
  
  	if ((got & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) == 0 ||
  	    (iocb->ki_filp->f_flags & O_DIRECT) ||
  	    (inode->i_sb->s_flags & MS_SYNCHRONOUS))
  		/* hmm, this isn't really async... */
  		ret = ceph_sync_read(filp, base, len, ppos, &checkeof);
  	else
  		ret = generic_file_aio_read(iocb, iov, nr_segs, pos);
  
  out:
  	dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
  	     inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);
  	ceph_put_cap_refs(ci, got);
  
  	if (checkeof && ret >= 0) {
  		int statret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);
  
  		/* hit EOF or hole? */
  		if (statret == 0 && *ppos < inode->i_size) {
  			dout("aio_read sync_read hit hole, reading more\n");
  			read += ret;
  			base += ret;
  			len -= ret;
  			checkeof = 0;
  			goto again;
  		}
  	}
  	if (ret >= 0)
  		ret += read;
  
  	return ret;
  }
  
  /*
   * Take cap references to avoid releasing caps to MDS mid-write.
   *
   * If we are synchronous, and write with an old snap context, the OSD
   * may return EOLDSNAPC.  In that case, retry the write.. _after_
   * dropping our cap refs and allowing the pending snap to logically
   * complete _before_ this write occurs.
   *
   * If we are near ENOSPC, write synchronously.
   */
  static ssize_t ceph_aio_write(struct kiocb *iocb, const struct iovec *iov,
  		       unsigned long nr_segs, loff_t pos)
  {
  	struct file *file = iocb->ki_filp;
  	struct ceph_file_info *fi = file->private_data;
  	struct inode *inode = file->f_dentry->d_inode;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_osd_client *osdc = &ceph_sb_to_client(inode->i_sb)->osdc;
  	loff_t endoff = pos + iov->iov_len;
  	int want, got = 0;
  	int ret, err;
  
  	if (ceph_snap(inode) != CEPH_NOSNAP)
  		return -EROFS;
  
  retry_snap:
  	if (ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_FULL))
  		return -ENOSPC;
  	__ceph_do_pending_vmtruncate(inode);
  	dout("aio_write %p %llx.%llx %llu~%u getting caps. i_size %llu\n",
  	     inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,
  	     inode->i_size);
  	if (fi->fmode & CEPH_FILE_MODE_LAZY)
  		want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
  	else
  		want = CEPH_CAP_FILE_BUFFER;
  	ret = ceph_get_caps(ci, CEPH_CAP_FILE_WR, want, &got, endoff);
  	if (ret < 0)
  		goto out;
  
  	dout("aio_write %p %llx.%llx %llu~%u  got cap refs on %s\n",
  	     inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,
  	     ceph_cap_string(got));
  
  	if ((got & (CEPH_CAP_FILE_BUFFER|CEPH_CAP_FILE_LAZYIO)) == 0 ||
  	    (iocb->ki_filp->f_flags & O_DIRECT) ||
  	    (inode->i_sb->s_flags & MS_SYNCHRONOUS)) {
  		ret = ceph_sync_write(file, iov->iov_base, iov->iov_len,
  			&iocb->ki_pos);
  	} else {
  		ret = generic_file_aio_write(iocb, iov, nr_segs, pos);
  
  		if ((ret >= 0 || ret == -EIOCBQUEUED) &&
  		    ((file->f_flags & O_SYNC) || IS_SYNC(file->f_mapping->host)
  		     || ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_NEARFULL))) {
  			err = vfs_fsync_range(file, pos, pos + ret - 1, 1);
  			if (err < 0)
  				ret = err;
  		}
  	}
  	if (ret >= 0) {
  		spin_lock(&inode->i_lock);
  		__ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR);
  		spin_unlock(&inode->i_lock);
  	}
  
  out:
  	dout("aio_write %p %llx.%llx %llu~%u  dropping cap refs on %s\n",
  	     inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,
  	     ceph_cap_string(got));
  	ceph_put_cap_refs(ci, got);
  
  	if (ret == -EOLDSNAPC) {
  		dout("aio_write %p %llx.%llx %llu~%u got EOLDSNAPC, retrying\n",
  		     inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len);
  		goto retry_snap;
  	}
  
  	return ret;
  }
  
  /*
   * llseek.  be sure to verify file size on SEEK_END.
   */
  static loff_t ceph_llseek(struct file *file, loff_t offset, int origin)
  {
  	struct inode *inode = file->f_mapping->host;
  	int ret;
  
  	mutex_lock(&inode->i_mutex);
  	__ceph_do_pending_vmtruncate(inode);
  	switch (origin) {
  	case SEEK_END:
  		ret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);
  		if (ret < 0) {
  			offset = ret;
  			goto out;
  		}
  		offset += inode->i_size;
  		break;
  	case SEEK_CUR:
  		/*
  		 * Here we special-case the lseek(fd, 0, SEEK_CUR)
  		 * position-querying operation.  Avoid rewriting the "same"
  		 * f_pos value back to the file because a concurrent read(),
  		 * write() or lseek() might have altered it
  		 */
  		if (offset == 0) {
  			offset = file->f_pos;
  			goto out;
  		}
  		offset += file->f_pos;
  		break;
  	}
  
  	if (offset < 0 || offset > inode->i_sb->s_maxbytes) {
  		offset = -EINVAL;
  		goto out;
  	}
  
  	/* Special lock needed here? */
  	if (offset != file->f_pos) {
  		file->f_pos = offset;
  		file->f_version = 0;
  	}
  
  out:
  	mutex_unlock(&inode->i_mutex);
  	return offset;
  }
  
  const struct file_operations ceph_file_fops = {
  	.open = ceph_open,
  	.release = ceph_release,
  	.llseek = ceph_llseek,
  	.read = do_sync_read,
  	.write = do_sync_write,
  	.aio_read = ceph_aio_read,
  	.aio_write = ceph_aio_write,
  	.mmap = ceph_mmap,
  	.fsync = ceph_fsync,
  	.lock = ceph_lock,
  	.flock = ceph_flock,
  	.splice_read = generic_file_splice_read,
  	.splice_write = generic_file_splice_write,
  	.unlocked_ioctl = ceph_ioctl,
  	.compat_ioctl	= ceph_ioctl,
  };
  
  