text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
   * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
   */
  
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/completion.h>
  #include <linux/buffer_head.h>
  #include <linux/pagemap.h>
  #include <linux/uio.h>
  #include <linux/blkdev.h>
  #include <linux/mm.h>
  #include <linux/mount.h>
  #include <linux/fs.h>
  #include <linux/gfs2_ondisk.h>
  #include <linux/falloc.h>
  #include <linux/swap.h>
  #include <linux/crc32.h>
  #include <linux/writeback.h>
  #include <linux/uaccess.h>
  #include <linux/dlm.h>
  #include <linux/dlm_plock.h>
  #include <linux/delay.h>
  #include <linux/backing-dev.h>
  
  #include "gfs2.h"
  #include "incore.h"
  #include "bmap.h"
  #include "aops.h"
  #include "dir.h"
  #include "glock.h"
  #include "glops.h"
  #include "inode.h"
  #include "log.h"
  #include "meta_io.h"
  #include "quota.h"
  #include "rgrp.h"
  #include "trans.h"
  #include "util.h"
  
  /**
   * gfs2_llseek - seek to a location in a file
   * @file: the file
   * @offset: the offset
   * @whence: Where to seek from (SEEK_SET, SEEK_CUR, or SEEK_END)
   *
   * SEEK_END requires the glock for the file because it references the
   * file's size.
   *
   * Returns: The new offset, or errno
   */
  
  static loff_t gfs2_llseek(struct file *file, loff_t offset, int whence)
  {
  	struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);
  	struct gfs2_holder i_gh;
  	loff_t error;
  
  	switch (whence) {
  	case SEEK_END:
  		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
  					   &i_gh);
  		if (!error) {
  			error = generic_file_llseek(file, offset, whence);
  			gfs2_glock_dq_uninit(&i_gh);
  		}
  		break;
  
  	case SEEK_DATA:
  		error = gfs2_seek_data(file, offset);
  		break;
  
  	case SEEK_HOLE:
  		error = gfs2_seek_hole(file, offset);
  		break;
  
  	case SEEK_CUR:
  	case SEEK_SET:
  		/*
  		 * These don't reference inode->i_size and don't depend on the
  		 * block mapping, so we don't need the glock.
  		 */
  		error = generic_file_llseek(file, offset, whence);
  		break;
  	default:
  		error = -EINVAL;
  	}
  
  	return error;
  }
  
  /**
   * gfs2_readdir - Iterator for a directory
   * @file: The directory to read from
   * @ctx: What to feed directory entries to
   *
   * Returns: errno
   */
  
  static int gfs2_readdir(struct file *file, struct dir_context *ctx)
  {
  	struct inode *dir = file->f_mapping->host;
  	struct gfs2_inode *dip = GFS2_I(dir);
  	struct gfs2_holder d_gh;
  	int error;
  
  	error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
  	if (error)
  		return error;
  
  	error = gfs2_dir_read(dir, ctx, &file->f_ra);
  
  	gfs2_glock_dq_uninit(&d_gh);
  
  	return error;
  }
  
  /**
   * fsflag_gfs2flag
   *
   * The FS_JOURNAL_DATA_FL flag maps to GFS2_DIF_INHERIT_JDATA for directories,
   * and to GFS2_DIF_JDATA for non-directories.
   */
  static struct {
  	u32 fsflag;
  	u32 gfsflag;
  } fsflag_gfs2flag[] = {
  	{FS_SYNC_FL, GFS2_DIF_SYNC},
  	{FS_IMMUTABLE_FL, GFS2_DIF_IMMUTABLE},
  	{FS_APPEND_FL, GFS2_DIF_APPENDONLY},
  	{FS_NOATIME_FL, GFS2_DIF_NOATIME},
  	{FS_INDEX_FL, GFS2_DIF_EXHASH},
  	{FS_TOPDIR_FL, GFS2_DIF_TOPDIR},
  	{FS_JOURNAL_DATA_FL, GFS2_DIF_JDATA | GFS2_DIF_INHERIT_JDATA},
  };
  
  static int gfs2_get_flags(struct file *filp, u32 __user *ptr)
  {
  	struct inode *inode = file_inode(filp);
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_holder gh;
  	int i, error;
  	u32 gfsflags, fsflags = 0;
  
  	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
  	error = gfs2_glock_nq(&gh);
  	if (error)
  		goto out_uninit;
  
  	gfsflags = ip->i_diskflags;
  	if (S_ISDIR(inode->i_mode))
  		gfsflags &= ~GFS2_DIF_JDATA;
  	else
  		gfsflags &= ~GFS2_DIF_INHERIT_JDATA;
  	for (i = 0; i < ARRAY_SIZE(fsflag_gfs2flag); i++)
  		if (gfsflags & fsflag_gfs2flag[i].gfsflag)
  			fsflags |= fsflag_gfs2flag[i].fsflag;
  
  	if (put_user(fsflags, ptr))
  		error = -EFAULT;
  
  	gfs2_glock_dq(&gh);
  out_uninit:
  	gfs2_holder_uninit(&gh);
  	return error;
  }
  
  void gfs2_set_inode_flags(struct inode *inode)
  {
  	struct gfs2_inode *ip = GFS2_I(inode);
  	unsigned int flags = inode->i_flags;
  
  	flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_NOSEC);
  	if ((ip->i_eattr == 0) && !is_sxid(inode->i_mode))
  		flags |= S_NOSEC;
  	if (ip->i_diskflags & GFS2_DIF_IMMUTABLE)
  		flags |= S_IMMUTABLE;
  	if (ip->i_diskflags & GFS2_DIF_APPENDONLY)
  		flags |= S_APPEND;
  	if (ip->i_diskflags & GFS2_DIF_NOATIME)
  		flags |= S_NOATIME;
  	if (ip->i_diskflags & GFS2_DIF_SYNC)
  		flags |= S_SYNC;
  	inode->i_flags = flags;
  }
  
  /* Flags that can be set by user space */
  #define GFS2_FLAGS_USER_SET (GFS2_DIF_JDATA|			\
  			     GFS2_DIF_IMMUTABLE|		\
  			     GFS2_DIF_APPENDONLY|		\
  			     GFS2_DIF_NOATIME|			\
  			     GFS2_DIF_SYNC|			\
  			     GFS2_DIF_TOPDIR|			\
  			     GFS2_DIF_INHERIT_JDATA)
  
  /**
   * do_gfs2_set_flags - set flags on an inode
   * @filp: file pointer
   * @reqflags: The flags to set
   * @mask: Indicates which flags are valid
   *
   */
  static int do_gfs2_set_flags(struct file *filp, u32 reqflags, u32 mask)
  {
  	struct inode *inode = file_inode(filp);
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  	struct buffer_head *bh;
  	struct gfs2_holder gh;
  	int error;
  	u32 new_flags, flags;
  
  	error = mnt_want_write_file(filp);
  	if (error)
  		return error;
  
  	error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
  	if (error)
  		goto out_drop_write;
  
  	error = -EACCES;
  	if (!inode_owner_or_capable(inode))
  		goto out;
  
  	error = 0;
  	flags = ip->i_diskflags;
  	new_flags = (flags & ~mask) | (reqflags & mask);
  	if ((new_flags ^ flags) == 0)
  		goto out;
  
  	error = -EPERM;
  	if (IS_IMMUTABLE(inode) && (new_flags & GFS2_DIF_IMMUTABLE))
  		goto out;
  	if (IS_APPEND(inode) && (new_flags & GFS2_DIF_APPENDONLY))
  		goto out;
  	if (((new_flags ^ flags) & GFS2_DIF_IMMUTABLE) &&
  	    !capable(CAP_LINUX_IMMUTABLE))
  		goto out;
  	if (!IS_IMMUTABLE(inode)) {
  		error = gfs2_permission(inode, MAY_WRITE);
  		if (error)
  			goto out;
  	}
  	if ((flags ^ new_flags) & GFS2_DIF_JDATA) {
  		if (new_flags & GFS2_DIF_JDATA)
  			gfs2_log_flush(sdp, ip->i_gl,
  				       GFS2_LOG_HEAD_FLUSH_NORMAL |
  				       GFS2_LFC_SET_FLAGS);
  		error = filemap_fdatawrite(inode->i_mapping);
  		if (error)
  			goto out;
  		error = filemap_fdatawait(inode->i_mapping);
  		if (error)
  			goto out;
  		if (new_flags & GFS2_DIF_JDATA)
  			gfs2_ordered_del_inode(ip);
  	}
  	error = gfs2_trans_begin(sdp, RES_DINODE, 0);
  	if (error)
  		goto out;
  	error = gfs2_meta_inode_buffer(ip, &bh);
  	if (error)
  		goto out_trans_end;
  	inode->i_ctime = current_time(inode);
  	gfs2_trans_add_meta(ip->i_gl, bh);
  	ip->i_diskflags = new_flags;
  	gfs2_dinode_out(ip, bh->b_data);
  	brelse(bh);
  	gfs2_set_inode_flags(inode);
  	gfs2_set_aops(inode);
  out_trans_end:
  	gfs2_trans_end(sdp);
  out:
  	gfs2_glock_dq_uninit(&gh);
  out_drop_write:
  	mnt_drop_write_file(filp);
  	return error;
  }
  
  static int gfs2_set_flags(struct file *filp, u32 __user *ptr)
  {
  	struct inode *inode = file_inode(filp);
  	u32 fsflags, gfsflags = 0;
  	u32 mask;
  	int i;
  
  	if (get_user(fsflags, ptr))
  		return -EFAULT;
  
  	for (i = 0; i < ARRAY_SIZE(fsflag_gfs2flag); i++) {
  		if (fsflags & fsflag_gfs2flag[i].fsflag) {
  			fsflags &= ~fsflag_gfs2flag[i].fsflag;
  			gfsflags |= fsflag_gfs2flag[i].gfsflag;
  		}
  	}
  	if (fsflags || gfsflags & ~GFS2_FLAGS_USER_SET)
  		return -EINVAL;
  
  	mask = GFS2_FLAGS_USER_SET;
  	if (S_ISDIR(inode->i_mode)) {
  		mask &= ~GFS2_DIF_JDATA;
  	} else {
  		/* The GFS2_DIF_TOPDIR flag is only valid for directories. */
  		if (gfsflags & GFS2_DIF_TOPDIR)
  			return -EINVAL;
  		mask &= ~(GFS2_DIF_TOPDIR | GFS2_DIF_INHERIT_JDATA);
  	}
  
  	return do_gfs2_set_flags(filp, gfsflags, mask);
  }
  
  static int gfs2_getlabel(struct file *filp, char __user *label)
  {
  	struct inode *inode = file_inode(filp);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  
  	if (copy_to_user(label, sdp->sd_sb.sb_locktable, GFS2_LOCKNAME_LEN))
  		return -EFAULT;
  
  	return 0;
  }
  
  static long gfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
  {
  	switch(cmd) {
  	case FS_IOC_GETFLAGS:
  		return gfs2_get_flags(filp, (u32 __user *)arg);
  	case FS_IOC_SETFLAGS:
  		return gfs2_set_flags(filp, (u32 __user *)arg);
  	case FITRIM:
  		return gfs2_fitrim(filp, (void __user *)arg);
  	case FS_IOC_GETFSLABEL:
  		return gfs2_getlabel(filp, (char __user *)arg);
  	}
  
  	return -ENOTTY;
  }
  
  /**
   * gfs2_size_hint - Give a hint to the size of a write request
   * @filep: The struct file
   * @offset: The file offset of the write
   * @size: The length of the write
   *
   * When we are about to do a write, this function records the total
   * write size in order to provide a suitable hint to the lower layers
   * about how many blocks will be required.
   *
   */
  
  static void gfs2_size_hint(struct file *filep, loff_t offset, size_t size)
  {
  	struct inode *inode = file_inode(filep);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  	struct gfs2_inode *ip = GFS2_I(inode);
  	size_t blks = (size + sdp->sd_sb.sb_bsize - 1) >> sdp->sd_sb.sb_bsize_shift;
  	int hint = min_t(size_t, INT_MAX, blks);
  
  	if (hint > atomic_read(&ip->i_sizehint))
  		atomic_set(&ip->i_sizehint, hint);
  }
  
  /**
   * gfs2_allocate_page_backing - Use bmap to allocate blocks
   * @page: The (locked) page to allocate backing for
   *
   * We try to allocate all the blocks required for the page in
   * one go. This might fail for various reasons, so we keep
   * trying until all the blocks to back this page are allocated.
   * If some of the blocks are already allocated, thats ok too.
   */
  
  static int gfs2_allocate_page_backing(struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	struct buffer_head bh;
  	unsigned long size = PAGE_SIZE;
  	u64 lblock = page->index << (PAGE_SHIFT - inode->i_blkbits);
  
  	do {
  		bh.b_state = 0;
  		bh.b_size = size;
  		gfs2_block_map(inode, lblock, &bh, 1);
  		if (!buffer_mapped(&bh))
  			return -EIO;
  		size -= bh.b_size;
  		lblock += (bh.b_size >> inode->i_blkbits);
  	} while(size > 0);
  	return 0;
  }
  
  /**
   * gfs2_page_mkwrite - Make a shared, mmap()ed, page writable
   * @vma: The virtual memory area
   * @vmf: The virtual memory fault containing the page to become writable
   *
   * When the page becomes writable, we need to ensure that we have
   * blocks allocated on disk to back that page.
   */
  
  static vm_fault_t gfs2_page_mkwrite(struct vm_fault *vmf)
  {
  	struct page *page = vmf->page;
  	struct inode *inode = file_inode(vmf->vma->vm_file);
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  	struct gfs2_alloc_parms ap = { .aflags = 0, };
  	unsigned long last_index;
  	u64 pos = page->index << PAGE_SHIFT;
  	unsigned int data_blocks, ind_blocks, rblocks;
  	struct gfs2_holder gh;
  	loff_t size;
  	int ret;
  
  	sb_start_pagefault(inode->i_sb);
  
  	ret = gfs2_rsqa_alloc(ip);
  	if (ret)
  		goto out;
  
  	gfs2_size_hint(vmf->vma->vm_file, pos, PAGE_SIZE);
  
  	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
  	ret = gfs2_glock_nq(&gh);
  	if (ret)
  		goto out_uninit;
  
  	/* Update file times before taking page lock */
  	file_update_time(vmf->vma->vm_file);
  
  	set_bit(GLF_DIRTY, &ip->i_gl->gl_flags);
  	set_bit(GIF_SW_PAGED, &ip->i_flags);
  
  	if (!gfs2_write_alloc_required(ip, pos, PAGE_SIZE)) {
  		lock_page(page);
  		if (!PageUptodate(page) || page->mapping != inode->i_mapping) {
  			ret = -EAGAIN;
  			unlock_page(page);
  		}
  		goto out_unlock;
  	}
  
  	ret = gfs2_rindex_update(sdp);
  	if (ret)
  		goto out_unlock;
  
  	gfs2_write_calc_reserv(ip, PAGE_SIZE, &data_blocks, &ind_blocks);
  	ap.target = data_blocks + ind_blocks;
  	ret = gfs2_quota_lock_check(ip, &ap);
  	if (ret)
  		goto out_unlock;
  	ret = gfs2_inplace_reserve(ip, &ap);
  	if (ret)
  		goto out_quota_unlock;
  
  	rblocks = RES_DINODE + ind_blocks;
  	if (gfs2_is_jdata(ip))
  		rblocks += data_blocks ? data_blocks : 1;
  	if (ind_blocks || data_blocks) {
  		rblocks += RES_STATFS + RES_QUOTA;
  		rblocks += gfs2_rg_blocks(ip, data_blocks + ind_blocks);
  	}
  	ret = gfs2_trans_begin(sdp, rblocks, 0);
  	if (ret)
  		goto out_trans_fail;
  
  	lock_page(page);
  	ret = -EINVAL;
  	size = i_size_read(inode);
  	last_index = (size - 1) >> PAGE_SHIFT;
  	/* Check page index against inode size */
  	if (size == 0 || (page->index > last_index))
  		goto out_trans_end;
  
  	ret = -EAGAIN;
  	/* If truncated, we must retry the operation, we may have raced
  	 * with the glock demotion code.
  	 */
  	if (!PageUptodate(page) || page->mapping != inode->i_mapping)
  		goto out_trans_end;
  
  	/* Unstuff, if required, and allocate backing blocks for page */
  	ret = 0;
  	if (gfs2_is_stuffed(ip))
  		ret = gfs2_unstuff_dinode(ip, page);
  	if (ret == 0)
  		ret = gfs2_allocate_page_backing(page);
  
  out_trans_end:
  	if (ret)
  		unlock_page(page);
  	gfs2_trans_end(sdp);
  out_trans_fail:
  	gfs2_inplace_release(ip);
  out_quota_unlock:
  	gfs2_quota_unlock(ip);
  out_unlock:
  	gfs2_glock_dq(&gh);
  out_uninit:
  	gfs2_holder_uninit(&gh);
  	if (ret == 0) {
  		set_page_dirty(page);
  		wait_for_stable_page(page);
  	}
  out:
  	sb_end_pagefault(inode->i_sb);
  	return block_page_mkwrite_return(ret);
  }
  
  static const struct vm_operations_struct gfs2_vm_ops = {
  	.fault = filemap_fault,
  	.map_pages = filemap_map_pages,
  	.page_mkwrite = gfs2_page_mkwrite,
  };
  
  /**
   * gfs2_mmap -
   * @file: The file to map
   * @vma: The VMA which described the mapping
   *
   * There is no need to get a lock here unless we should be updating
   * atime. We ignore any locking errors since the only consequence is
   * a missed atime update (which will just be deferred until later).
   *
   * Returns: 0
   */
  
  static int gfs2_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);
  
  	if (!(file->f_flags & O_NOATIME) &&
  	    !IS_NOATIME(&ip->i_inode)) {
  		struct gfs2_holder i_gh;
  		int error;
  
  		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
  					   &i_gh);
  		if (error)
  			return error;
  		/* grab lock to update inode */
  		gfs2_glock_dq_uninit(&i_gh);
  		file_accessed(file);
  	}
  	vma->vm_ops = &gfs2_vm_ops;
  
  	return 0;
  }
  
  /**
   * gfs2_open_common - This is common to open and atomic_open
   * @inode: The inode being opened
   * @file: The file being opened
   *
   * This maybe called under a glock or not depending upon how it has
   * been called. We must always be called under a glock for regular
   * files, however. For other file types, it does not matter whether
   * we hold the glock or not.
   *
   * Returns: Error code or 0 for success
   */
  
  int gfs2_open_common(struct inode *inode, struct file *file)
  {
  	struct gfs2_file *fp;
  	int ret;
  
  	if (S_ISREG(inode->i_mode)) {
  		ret = generic_file_open(inode, file);
  		if (ret)
  			return ret;
  	}
  
  	fp = kzalloc(sizeof(struct gfs2_file), GFP_NOFS);
  	if (!fp)
  		return -ENOMEM;
  
  	mutex_init(&fp->f_fl_mutex);
  
  	gfs2_assert_warn(GFS2_SB(inode), !file->private_data);
  	file->private_data = fp;
  	return 0;
  }
  
  /**
   * gfs2_open - open a file
   * @inode: the inode to open
   * @file: the struct file for this opening
   *
   * After atomic_open, this function is only used for opening files
   * which are already cached. We must still get the glock for regular
   * files to ensure that we have the file size uptodate for the large
   * file check which is in the common code. That is only an issue for
   * regular files though.
   *
   * Returns: errno
   */
  
  static int gfs2_open(struct inode *inode, struct file *file)
  {
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_holder i_gh;
  	int error;
  	bool need_unlock = false;
  
  	if (S_ISREG(ip->i_inode.i_mode)) {
  		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
  					   &i_gh);
  		if (error)
  			return error;
  		need_unlock = true;
  	}
  
  	error = gfs2_open_common(inode, file);
  
  	if (need_unlock)
  		gfs2_glock_dq_uninit(&i_gh);
  
  	return error;
  }
  
  /**
   * gfs2_release - called to close a struct file
   * @inode: the inode the struct file belongs to
   * @file: the struct file being closed
   *
   * Returns: errno
   */
  
  static int gfs2_release(struct inode *inode, struct file *file)
  {
  	struct gfs2_inode *ip = GFS2_I(inode);
  
  	kfree(file->private_data);
  	file->private_data = NULL;
  
  	if (!(file->f_mode & FMODE_WRITE))
  		return 0;
  
  	gfs2_rsqa_delete(ip, &inode->i_writecount);
  	return 0;
  }
  
  /**
   * gfs2_fsync - sync the dirty data for a file (across the cluster)
   * @file: the file that points to the dentry
   * @start: the start position in the file to sync
   * @end: the end position in the file to sync
   * @datasync: set if we can ignore timestamp changes
   *
   * We split the data flushing here so that we don't wait for the data
   * until after we've also sent the metadata to disk. Note that for
   * data=ordered, we will write & wait for the data at the log flush
   * stage anyway, so this is unlikely to make much of a difference
   * except in the data=writeback case.
   *
   * If the fdatawrite fails due to any reason except -EIO, we will
   * continue the remainder of the fsync, although we'll still report
   * the error at the end. This is to match filemap_write_and_wait_range()
   * behaviour.
   *
   * Returns: errno
   */
  
  static int gfs2_fsync(struct file *file, loff_t start, loff_t end,
  		      int datasync)
  {
  	struct address_space *mapping = file->f_mapping;
  	struct inode *inode = mapping->host;
  	int sync_state = inode->i_state & I_DIRTY_ALL;
  	struct gfs2_inode *ip = GFS2_I(inode);
  	int ret = 0, ret1 = 0;
  
  	if (mapping->nrpages) {
  		ret1 = filemap_fdatawrite_range(mapping, start, end);
  		if (ret1 == -EIO)
  			return ret1;
  	}
  
  	if (!gfs2_is_jdata(ip))
  		sync_state &= ~I_DIRTY_PAGES;
  	if (datasync)
  		sync_state &= ~(I_DIRTY_SYNC | I_DIRTY_TIME);
  
  	if (sync_state) {
  		ret = sync_inode_metadata(inode, 1);
  		if (ret)
  			return ret;
  		if (gfs2_is_jdata(ip))
  			ret = file_write_and_wait(file);
  		if (ret)
  			return ret;
  		gfs2_ail_flush(ip->i_gl, 1);
  	}
  
  	if (mapping->nrpages)
  		ret = file_fdatawait_range(file, start, end);
  
  	return ret ? ret : ret1;
  }
  
  static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to)
  {
  	struct file *file = iocb->ki_filp;
  	struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);
  	size_t count = iov_iter_count(to);
  	struct gfs2_holder gh;
  	ssize_t ret;
  
  	if (!count)
  		return 0; /* skip atime */
  
  	gfs2_holder_init(ip->i_gl, LM_ST_DEFERRED, 0, &gh);
  	ret = gfs2_glock_nq(&gh);
  	if (ret)
  		goto out_uninit;
  
  	ret = iomap_dio_rw(iocb, to, &gfs2_iomap_ops, NULL);
  
  	gfs2_glock_dq(&gh);
  out_uninit:
  	gfs2_holder_uninit(&gh);
  	return ret;
  }
  
  static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file->f_mapping->host;
  	struct gfs2_inode *ip = GFS2_I(inode);
  	size_t len = iov_iter_count(from);
  	loff_t offset = iocb->ki_pos;
  	struct gfs2_holder gh;
  	ssize_t ret;
  
  	/*
  	 * Deferred lock, even if its a write, since we do no allocation on
  	 * this path. All we need to change is the atime, and this lock mode
  	 * ensures that other nodes have flushed their buffered read caches
  	 * (i.e. their page cache entries for this inode). We do not,
  	 * unfortunately, have the option of only flushing a range like the
  	 * VFS does.
  	 */
  	gfs2_holder_init(ip->i_gl, LM_ST_DEFERRED, 0, &gh);
  	ret = gfs2_glock_nq(&gh);
  	if (ret)
  		goto out_uninit;
  
  	/* Silently fall back to buffered I/O when writing beyond EOF */
  	if (offset + len > i_size_read(&ip->i_inode))
  		goto out;
  
  	ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL);
  
  out:
  	gfs2_glock_dq(&gh);
  out_uninit:
  	gfs2_holder_uninit(&gh);
  	return ret;
  }
  
  static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
  {
  	ssize_t ret;
  
  	if (iocb->ki_flags & IOCB_DIRECT) {
  		ret = gfs2_file_direct_read(iocb, to);
  		if (likely(ret != -ENOTBLK))
  			return ret;
  		iocb->ki_flags &= ~IOCB_DIRECT;
  	}
  	return generic_file_read_iter(iocb, to);
  }
  
  /**
   * gfs2_file_write_iter - Perform a write to a file
   * @iocb: The io context
   * @from: The data to write
   *
   * We have to do a lock/unlock here to refresh the inode size for
   * O_APPEND writes, otherwise we can land up writing at the wrong
   * offset. There is still a race, but provided the app is using its
   * own file locking, this will make O_APPEND work as expected.
   *
   */
  
  static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file_inode(file);
  	struct gfs2_inode *ip = GFS2_I(inode);
  	ssize_t written = 0, ret;
  
  	ret = gfs2_rsqa_alloc(ip);
  	if (ret)
  		return ret;
  
  	gfs2_size_hint(file, iocb->ki_pos, iov_iter_count(from));
  
  	if (iocb->ki_flags & IOCB_APPEND) {
  		struct gfs2_holder gh;
  
  		ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
  		if (ret)
  			return ret;
  		gfs2_glock_dq_uninit(&gh);
  	}
  
  	inode_lock(inode);
  	ret = generic_write_checks(iocb, from);
  	if (ret <= 0)
  		goto out;
  
  	/* We can write back this queue in page reclaim */
  	current->backing_dev_info = inode_to_bdi(inode);
  
  	ret = file_remove_privs(file);
  	if (ret)
  		goto out2;
  
  	ret = file_update_time(file);
  	if (ret)
  		goto out2;
  
  	if (iocb->ki_flags & IOCB_DIRECT) {
  		struct address_space *mapping = file->f_mapping;
  		loff_t pos, endbyte;
  		ssize_t buffered;
  
  		written = gfs2_file_direct_write(iocb, from);
  		if (written < 0 || !iov_iter_count(from))
  			goto out2;
  
  		ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
  		if (unlikely(ret < 0))
  			goto out2;
  		buffered = ret;
  
  		/*
  		 * We need to ensure that the page cache pages are written to
  		 * disk and invalidated to preserve the expected O_DIRECT
  		 * semantics.
  		 */
  		pos = iocb->ki_pos;
  		endbyte = pos + buffered - 1;
  		ret = filemap_write_and_wait_range(mapping, pos, endbyte);
  		if (!ret) {
  			iocb->ki_pos += buffered;
  			written += buffered;
  			invalidate_mapping_pages(mapping,
  						 pos >> PAGE_SHIFT,
  						 endbyte >> PAGE_SHIFT);
  		} else {
  			/*
  			 * We don't know how much we wrote, so just return
  			 * the number of bytes which were direct-written
  			 */
  		}
  	} else {
  		ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
  		if (likely(ret > 0))
  			iocb->ki_pos += ret;
  	}
  
  out2:
  	current->backing_dev_info = NULL;
  out:
  	inode_unlock(inode);
  	if (likely(ret > 0)) {
  		/* Handle various SYNC-type writes */
  		ret = generic_write_sync(iocb, ret);
  	}
  	return written ? written : ret;
  }
  
  static int fallocate_chunk(struct inode *inode, loff_t offset, loff_t len,
  			   int mode)
  {
  	struct super_block *sb = inode->i_sb;
  	struct gfs2_inode *ip = GFS2_I(inode);
  	loff_t end = offset + len;
  	struct buffer_head *dibh;
  	int error;
  
  	error = gfs2_meta_inode_buffer(ip, &dibh);
  	if (unlikely(error))
  		return error;
  
  	gfs2_trans_add_meta(ip->i_gl, dibh);
  
  	if (gfs2_is_stuffed(ip)) {
  		error = gfs2_unstuff_dinode(ip, NULL);
  		if (unlikely(error))
  			goto out;
  	}
  
  	while (offset < end) {
  		struct iomap iomap = { };
  
  		error = gfs2_iomap_get_alloc(inode, offset, end - offset,
  					     &iomap);
  		if (error)
  			goto out;
  		offset = iomap.offset + iomap.length;
  		if (!(iomap.flags & IOMAP_F_NEW))
  			continue;
  		error = sb_issue_zeroout(sb, iomap.addr >> inode->i_blkbits,
  					 iomap.length >> inode->i_blkbits,
  					 GFP_NOFS);
  		if (error) {
  			fs_err(GFS2_SB(inode), "Failed to zero data buffers\n");
  			goto out;
  		}
  	}
  out:
  	brelse(dibh);
  	return error;
  }
  /**
   * calc_max_reserv() - Reverse of write_calc_reserv. Given a number of
   *                     blocks, determine how many bytes can be written.
   * @ip:          The inode in question.
   * @len:         Max cap of bytes. What we return in *len must be <= this.
   * @data_blocks: Compute and return the number of data blocks needed
   * @ind_blocks:  Compute and return the number of indirect blocks needed
   * @max_blocks:  The total blocks available to work with.
   *
   * Returns: void, but @len, @data_blocks and @ind_blocks are filled in.
   */
  static void calc_max_reserv(struct gfs2_inode *ip, loff_t *len,
  			    unsigned int *data_blocks, unsigned int *ind_blocks,
  			    unsigned int max_blocks)
  {
  	loff_t max = *len;
  	const struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
  	unsigned int tmp, max_data = max_blocks - 3 * (sdp->sd_max_height - 1);
  
  	for (tmp = max_data; tmp > sdp->sd_diptrs;) {
  		tmp = DIV_ROUND_UP(tmp, sdp->sd_inptrs);
  		max_data -= tmp;
  	}
  
  	*data_blocks = max_data;
  	*ind_blocks = max_blocks - max_data;
  	*len = ((loff_t)max_data - 3) << sdp->sd_sb.sb_bsize_shift;
  	if (*len > max) {
  		*len = max;
  		gfs2_write_calc_reserv(ip, max, data_blocks, ind_blocks);
  	}
  }
  
  static long __gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
  {
  	struct inode *inode = file_inode(file);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_alloc_parms ap = { .aflags = 0, };
  	unsigned int data_blocks = 0, ind_blocks = 0, rblocks;
  	loff_t bytes, max_bytes, max_blks;
  	int error;
  	const loff_t pos = offset;
  	const loff_t count = len;
  	loff_t bsize_mask = ~((loff_t)sdp->sd_sb.sb_bsize - 1);
  	loff_t next = (offset + len - 1) >> sdp->sd_sb.sb_bsize_shift;
  	loff_t max_chunk_size = UINT_MAX & bsize_mask;
  
  	next = (next + 1) << sdp->sd_sb.sb_bsize_shift;
  
  	offset &= bsize_mask;
  
  	len = next - offset;
  	bytes = sdp->sd_max_rg_data * sdp->sd_sb.sb_bsize / 2;
  	if (!bytes)
  		bytes = UINT_MAX;
  	bytes &= bsize_mask;
  	if (bytes == 0)
  		bytes = sdp->sd_sb.sb_bsize;
  
  	gfs2_size_hint(file, offset, len);
  
  	gfs2_write_calc_reserv(ip, PAGE_SIZE, &data_blocks, &ind_blocks);
  	ap.min_target = data_blocks + ind_blocks;
  
  	while (len > 0) {
  		if (len < bytes)
  			bytes = len;
  		if (!gfs2_write_alloc_required(ip, offset, bytes)) {
  			len -= bytes;
  			offset += bytes;
  			continue;
  		}
  
  		/* We need to determine how many bytes we can actually
  		 * fallocate without exceeding quota or going over the
  		 * end of the fs. We start off optimistically by assuming
  		 * we can write max_bytes */
  		max_bytes = (len > max_chunk_size) ? max_chunk_size : len;
  
  		/* Since max_bytes is most likely a theoretical max, we
  		 * calculate a more realistic 'bytes' to serve as a good
  		 * starting point for the number of bytes we may be able
  		 * to write */
  		gfs2_write_calc_reserv(ip, bytes, &data_blocks, &ind_blocks);
  		ap.target = data_blocks + ind_blocks;
  
  		error = gfs2_quota_lock_check(ip, &ap);
  		if (error)
  			return error;
  		/* ap.allowed tells us how many blocks quota will allow
  		 * us to write. Check if this reduces max_blks */
  		max_blks = UINT_MAX;
  		if (ap.allowed)
  			max_blks = ap.allowed;
  
  		error = gfs2_inplace_reserve(ip, &ap);
  		if (error)
  			goto out_qunlock;
  
  		/* check if the selected rgrp limits our max_blks further */
  		if (ap.allowed && ap.allowed < max_blks)
  			max_blks = ap.allowed;
  
  		/* Almost done. Calculate bytes that can be written using
  		 * max_blks. We also recompute max_bytes, data_blocks and
  		 * ind_blocks */
  		calc_max_reserv(ip, &max_bytes, &data_blocks,
  				&ind_blocks, max_blks);
  
  		rblocks = RES_DINODE + ind_blocks + RES_STATFS + RES_QUOTA +
  			  RES_RG_HDR + gfs2_rg_blocks(ip, data_blocks + ind_blocks);
  		if (gfs2_is_jdata(ip))
  			rblocks += data_blocks ? data_blocks : 1;
  
  		error = gfs2_trans_begin(sdp, rblocks,
  					 PAGE_SIZE/sdp->sd_sb.sb_bsize);
  		if (error)
  			goto out_trans_fail;
  
  		error = fallocate_chunk(inode, offset, max_bytes, mode);
  		gfs2_trans_end(sdp);
  
  		if (error)
  			goto out_trans_fail;
  
  		len -= max_bytes;
  		offset += max_bytes;
  		gfs2_inplace_release(ip);
  		gfs2_quota_unlock(ip);
  	}
  
  	if (!(mode & FALLOC_FL_KEEP_SIZE) && (pos + count) > inode->i_size) {
  		i_size_write(inode, pos + count);
  		file_update_time(file);
  		mark_inode_dirty(inode);
  	}
  
  	if ((file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host))
  		return vfs_fsync_range(file, pos, pos + count - 1,
  			       (file->f_flags & __O_SYNC) ? 0 : 1);
  	return 0;
  
  out_trans_fail:
  	gfs2_inplace_release(ip);
  out_qunlock:
  	gfs2_quota_unlock(ip);
  	return error;
  }
  
  static long gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
  {
  	struct inode *inode = file_inode(file);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_holder gh;
  	int ret;
  
  	if (mode & ~(FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE))
  		return -EOPNOTSUPP;
  	/* fallocate is needed by gfs2_grow to reserve space in the rindex */
  	if (gfs2_is_jdata(ip) && inode != sdp->sd_rindex)
  		return -EOPNOTSUPP;
  
  	inode_lock(inode);
  
  	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
  	ret = gfs2_glock_nq(&gh);
  	if (ret)
  		goto out_uninit;
  
  	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
  	    (offset + len) > inode->i_size) {
  		ret = inode_newsize_ok(inode, offset + len);
  		if (ret)
  			goto out_unlock;
  	}
  
  	ret = get_write_access(inode);
  	if (ret)
  		goto out_unlock;
  
  	if (mode & FALLOC_FL_PUNCH_HOLE) {
  		ret = __gfs2_punch_hole(file, offset, len);
  	} else {
  		ret = gfs2_rsqa_alloc(ip);
  		if (ret)
  			goto out_putw;
  
  		ret = __gfs2_fallocate(file, mode, offset, len);
  
  		if (ret)
  			gfs2_rs_deltree(&ip->i_res);
  	}
  
  out_putw:
  	put_write_access(inode);
  out_unlock:
  	gfs2_glock_dq(&gh);
  out_uninit:
  	gfs2_holder_uninit(&gh);
  	inode_unlock(inode);
  	return ret;
  }
  
  static ssize_t gfs2_file_splice_write(struct pipe_inode_info *pipe,
  				      struct file *out, loff_t *ppos,
  				      size_t len, unsigned int flags)
  {
  	int error;
  	struct gfs2_inode *ip = GFS2_I(out->f_mapping->host);
  
  	error = gfs2_rsqa_alloc(ip);
  	if (error)
  		return (ssize_t)error;
  
  	gfs2_size_hint(out, *ppos, len);
  
  	return iter_file_splice_write(pipe, out, ppos, len, flags);
  }
  
  #ifdef CONFIG_GFS2_FS_LOCKING_DLM
  
  /**
   * gfs2_lock - acquire/release a posix lock on a file
   * @file: the file pointer
   * @cmd: either modify or retrieve lock state, possibly wait
   * @fl: type and range of lock
   *
   * Returns: errno
   */
  
  static int gfs2_lock(struct file *file, int cmd, struct file_lock *fl)
  {
  	struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);
  	struct gfs2_sbd *sdp = GFS2_SB(file->f_mapping->host);
  	struct lm_lockstruct *ls = &sdp->sd_lockstruct;
  
  	if (!(fl->fl_flags & FL_POSIX))
  		return -ENOLCK;
  	if (__mandatory_lock(&ip->i_inode) && fl->fl_type != F_UNLCK)
  		return -ENOLCK;
  
  	if (cmd == F_CANCELLK) {
  		/* Hack: */
  		cmd = F_SETLK;
  		fl->fl_type = F_UNLCK;
  	}
  	if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) {
  		if (fl->fl_type == F_UNLCK)
  			locks_lock_file_wait(file, fl);
  		return -EIO;
  	}
  	if (IS_GETLK(cmd))
  		return dlm_posix_get(ls->ls_dlm, ip->i_no_addr, file, fl);
  	else if (fl->fl_type == F_UNLCK)
  		return dlm_posix_unlock(ls->ls_dlm, ip->i_no_addr, file, fl);
  	else
  		return dlm_posix_lock(ls->ls_dlm, ip->i_no_addr, file, cmd, fl);
  }
  
  static int do_flock(struct file *file, int cmd, struct file_lock *fl)
  {
  	struct gfs2_file *fp = file->private_data;
  	struct gfs2_holder *fl_gh = &fp->f_fl_gh;
  	struct gfs2_inode *ip = GFS2_I(file_inode(file));
  	struct gfs2_glock *gl;
  	unsigned int state;
  	u16 flags;
  	int error = 0;
  	int sleeptime;
  
  	state = (fl->fl_type == F_WRLCK) ? LM_ST_EXCLUSIVE : LM_ST_SHARED;
  	flags = (IS_SETLKW(cmd) ? 0 : LM_FLAG_TRY_1CB) | GL_EXACT;
  
  	mutex_lock(&fp->f_fl_mutex);
  
  	if (gfs2_holder_initialized(fl_gh)) {
  		struct file_lock request;
  		if (fl_gh->gh_state == state)
  			goto out;
  		locks_init_lock(&request);
  		request.fl_type = F_UNLCK;
  		request.fl_flags = FL_FLOCK;
  		locks_lock_file_wait(file, &request);
  		gfs2_glock_dq(fl_gh);
  		gfs2_holder_reinit(state, flags, fl_gh);
  	} else {
  		error = gfs2_glock_get(GFS2_SB(&ip->i_inode), ip->i_no_addr,
  				       &gfs2_flock_glops, CREATE, &gl);
  		if (error)
  			goto out;
  		gfs2_holder_init(gl, state, flags, fl_gh);
  		gfs2_glock_put(gl);
  	}
  	for (sleeptime = 1; sleeptime <= 4; sleeptime <<= 1) {
  		error = gfs2_glock_nq(fl_gh);
  		if (error != GLR_TRYFAILED)
  			break;
  		fl_gh->gh_flags = LM_FLAG_TRY | GL_EXACT;
  		fl_gh->gh_error = 0;
  		msleep(sleeptime);
  	}
  	if (error) {
  		gfs2_holder_uninit(fl_gh);
  		if (error == GLR_TRYFAILED)
  			error = -EAGAIN;
  	} else {
  		error = locks_lock_file_wait(file, fl);
  		gfs2_assert_warn(GFS2_SB(&ip->i_inode), !error);
  	}
  
  out:
  	mutex_unlock(&fp->f_fl_mutex);
  	return error;
  }
  
  static void do_unflock(struct file *file, struct file_lock *fl)
  {
  	struct gfs2_file *fp = file->private_data;
  	struct gfs2_holder *fl_gh = &fp->f_fl_gh;
  
  	mutex_lock(&fp->f_fl_mutex);
  	locks_lock_file_wait(file, fl);
  	if (gfs2_holder_initialized(fl_gh)) {
  		gfs2_glock_dq(fl_gh);
  		gfs2_holder_uninit(fl_gh);
  	}
  	mutex_unlock(&fp->f_fl_mutex);
  }
  
  /**
   * gfs2_flock - acquire/release a flock lock on a file
   * @file: the file pointer
   * @cmd: either modify or retrieve lock state, possibly wait
   * @fl: type and range of lock
   *
   * Returns: errno
   */
  
  static int gfs2_flock(struct file *file, int cmd, struct file_lock *fl)
  {
  	if (!(fl->fl_flags & FL_FLOCK))
  		return -ENOLCK;
  	if (fl->fl_type & LOCK_MAND)
  		return -EOPNOTSUPP;
  
  	if (fl->fl_type == F_UNLCK) {
  		do_unflock(file, fl);
  		return 0;
  	} else {
  		return do_flock(file, cmd, fl);
  	}
  }
  
  const struct file_operations gfs2_file_fops = {
  	.llseek		= gfs2_llseek,
  	.read_iter	= gfs2_file_read_iter,
  	.write_iter	= gfs2_file_write_iter,
  	.iopoll		= iomap_dio_iopoll,
  	.unlocked_ioctl	= gfs2_ioctl,
  	.mmap		= gfs2_mmap,
  	.open		= gfs2_open,
  	.release	= gfs2_release,
  	.fsync		= gfs2_fsync,
  	.lock		= gfs2_lock,
  	.flock		= gfs2_flock,
  	.splice_read	= generic_file_splice_read,
  	.splice_write	= gfs2_file_splice_write,
  	.setlease	= simple_nosetlease,
  	.fallocate	= gfs2_fallocate,
  };
  
  const struct file_operations gfs2_dir_fops = {
  	.iterate_shared	= gfs2_readdir,
  	.unlocked_ioctl	= gfs2_ioctl,
  	.open		= gfs2_open,
  	.release	= gfs2_release,
  	.fsync		= gfs2_fsync,
  	.lock		= gfs2_lock,
  	.flock		= gfs2_flock,
  	.llseek		= default_llseek,
  };
  
  #endif /* CONFIG_GFS2_FS_LOCKING_DLM */
  
  const struct file_operations gfs2_file_fops_nolock = {
  	.llseek		= gfs2_llseek,
  	.read_iter	= gfs2_file_read_iter,
  	.write_iter	= gfs2_file_write_iter,
  	.iopoll		= iomap_dio_iopoll,
  	.unlocked_ioctl	= gfs2_ioctl,
  	.mmap		= gfs2_mmap,
  	.open		= gfs2_open,
  	.release	= gfs2_release,
  	.fsync		= gfs2_fsync,
  	.splice_read	= generic_file_splice_read,
  	.splice_write	= gfs2_file_splice_write,
  	.setlease	= generic_setlease,
  	.fallocate	= gfs2_fallocate,
  };
  
  const struct file_operations gfs2_dir_fops_nolock = {
  	.iterate_shared	= gfs2_readdir,
  	.unlocked_ioctl	= gfs2_ioctl,
  	.open		= gfs2_open,
  	.release	= gfs2_release,
  	.fsync		= gfs2_fsync,
  	.llseek		= default_llseek,
  };
  
  