// 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/compat.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 <linux/fileattr.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;
}

/*
 * struct 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 inline u32 gfs2_gfsflags_to_fsflags(struct inode *inode, u32 gfsflags)
{
	int i;
	u32 fsflags = 0;

	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;
	return fsflags;
}

int gfs2_fileattr_get(struct dentry *dentry, struct fileattr *fa)
{
	struct inode *inode = d_inode(dentry);
	struct gfs2_inode *ip = GFS2_I(inode);
	struct gfs2_holder gh;
	int error;
	u32 fsflags;

	if (d_is_special(dentry))
		return -ENOTTY;

	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
	error = gfs2_glock_nq(&gh);
	if (error)
		goto out_uninit;

	fsflags = gfs2_gfsflags_to_fsflags(inode, ip->i_diskflags);

	fileattr_fill_flags(fa, fsflags);

	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
 * @inode: The inode
 * @reqflags: The flags to set
 * @mask: Indicates which flags are valid
 * @fsflags: The FS_* inode flags passed in
 *
 */
static int do_gfs2_set_flags(struct inode *inode, u32 reqflags, u32 mask,
			     const u32 fsflags)
{
	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 = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
	if (error)
		return error;

	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 (!IS_IMMUTABLE(inode)) {
		error = gfs2_permission(&init_user_ns, 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);
	return error;
}

int gfs2_fileattr_set(struct user_namespace *mnt_userns,
		      struct dentry *dentry, struct fileattr *fa)
{
	struct inode *inode = d_inode(dentry);
	u32 fsflags = fa->flags, gfsflags = 0;
	u32 mask;
	int i;

	if (d_is_special(dentry))
		return -ENOTTY;

	if (fileattr_has_fsx(fa))
		return -EOPNOTSUPP;

	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(inode, gfsflags, mask, fsflags);
}

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 FITRIM:
		return gfs2_fitrim(filp, (void __user *)arg);
	case FS_IOC_GETFSLABEL:
		return gfs2_getlabel(filp, (char __user *)arg);
	}

	return -ENOTTY;
}

#ifdef CONFIG_COMPAT
static long gfs2_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	switch(cmd) {
	/* Keep this list in sync with gfs2_ioctl */
	case FITRIM:
	case FS_IOC_GETFSLABEL:
		break;
	default:
		return -ENOIOCTLCMD;
	}

	return gfs2_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
}
#else
#define gfs2_compat_ioctl NULL
#endif

/**
 * 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 - Allocate blocks for a write fault
 * @page: The (locked) page to allocate backing for
 * @length: Size of the allocation
 *
 * 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,
 * that is ok too.
 */
static int gfs2_allocate_page_backing(struct page *page, unsigned int length)
{
	u64 pos = page_offset(page);

	do {
		struct iomap iomap = { };

		if (gfs2_iomap_alloc(page->mapping->host, pos, length, &iomap))
			return -EIO;

		if (length < iomap.length)
			iomap.length = length;
		length -= iomap.length;
		pos += iomap.length;
	} while (length > 0);

	return 0;
}

/**
 * gfs2_page_mkwrite - Make a shared, mmap()ed, page writable
 * @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, };
	u64 offset = page_offset(page);
	unsigned int data_blocks, ind_blocks, rblocks;
	vm_fault_t ret = VM_FAULT_LOCKED;
	struct gfs2_holder gh;
	unsigned int length;
	loff_t size;
	int err;

	sb_start_pagefault(inode->i_sb);

	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
	err = gfs2_glock_nq(&gh);
	if (err) {
		ret = block_page_mkwrite_return(err);
		goto out_uninit;
	}

	/* Check page index against inode size */
	size = i_size_read(inode);
	if (offset >= size) {
		ret = VM_FAULT_SIGBUS;
		goto out_unlock;
	}

	/* Update file times before taking page lock */
	file_update_time(vmf->vma->vm_file);

	/* page is wholly or partially inside EOF */
	if (size - offset < PAGE_SIZE)
		length = size - offset;
	else
		length = PAGE_SIZE;

	gfs2_size_hint(vmf->vma->vm_file, offset, length);

	set_bit(GLF_DIRTY, &ip->i_gl->gl_flags);
	set_bit(GIF_SW_PAGED, &ip->i_flags);

	/*
	 * iomap_writepage / iomap_writepages currently don't support inline
	 * files, so always unstuff here.
	 */

	if (!gfs2_is_stuffed(ip) &&
	    !gfs2_write_alloc_required(ip, offset, length)) {
		lock_page(page);
		if (!PageUptodate(page) || page->mapping != inode->i_mapping) {
			ret = VM_FAULT_NOPAGE;
			unlock_page(page);
		}
		goto out_unlock;
	}

	err = gfs2_rindex_update(sdp);
	if (err) {
		ret = block_page_mkwrite_return(err);
		goto out_unlock;
	}

	gfs2_write_calc_reserv(ip, length, &data_blocks, &ind_blocks);
	ap.target = data_blocks + ind_blocks;
	err = gfs2_quota_lock_check(ip, &ap);
	if (err) {
		ret = block_page_mkwrite_return(err);
		goto out_unlock;
	}
	err = gfs2_inplace_reserve(ip, &ap);
	if (err) {
		ret = block_page_mkwrite_return(err);
		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);
	}
	err = gfs2_trans_begin(sdp, rblocks, 0);
	if (err) {
		ret = block_page_mkwrite_return(err);
		goto out_trans_fail;
	}

	/* Unstuff, if required, and allocate backing blocks for page */
	if (gfs2_is_stuffed(ip)) {
		err = gfs2_unstuff_dinode(ip);
		if (err) {
			ret = block_page_mkwrite_return(err);
			goto out_trans_end;
		}
	}

	lock_page(page);
	/* If truncated, we must retry the operation, we may have raced
	 * with the glock demotion code.
	 */
	if (!PageUptodate(page) || page->mapping != inode->i_mapping) {
		ret = VM_FAULT_NOPAGE;
		goto out_page_locked;
	}

	err = gfs2_allocate_page_backing(page, length);
	if (err)
		ret = block_page_mkwrite_return(err);

out_page_locked:
	if (ret != VM_FAULT_LOCKED)
		unlock_page(page);
out_trans_end:
	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 == VM_FAULT_LOCKED) {
		set_page_dirty(page);
		wait_for_stable_page(page);
	}
	sb_end_pagefault(inode->i_sb);
	return ret;
}

static vm_fault_t gfs2_fault(struct vm_fault *vmf)
{
	struct inode *inode = file_inode(vmf->vma->vm_file);
	struct gfs2_inode *ip = GFS2_I(inode);
	struct gfs2_holder gh;
	vm_fault_t ret;
	int err;

	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
	err = gfs2_glock_nq(&gh);
	if (err) {
		ret = block_page_mkwrite_return(err);
		goto out_uninit;
	}
	ret = filemap_fault(vmf);
	gfs2_glock_dq(&gh);
out_uninit:
	gfs2_holder_uninit(&gh);
	return ret;
}

static const struct vm_operations_struct gfs2_vm_ops = {
	.fault = gfs2_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;
	if (file->f_mode & FMODE_WRITE) {
		ret = gfs2_qa_get(GFS2_I(inode));
		if (ret)
			goto fail;
	}
	return 0;

fail:
	kfree(file->private_data);
	file->private_data = NULL;
	return ret;
}

/**
 * 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 (gfs2_rs_active(&ip->i_res))
		gfs2_rs_delete(ip, &inode->i_writecount);
	if (file->f_mode & FMODE_WRITE)
		gfs2_qa_put(ip);
	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;
	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;

	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 gfs2_holder *gh)
{
	struct file *file = iocb->ki_filp;
	struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);
	size_t count = iov_iter_count(to);
	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, 0);
	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 gfs2_holder *gh)
{
	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;
	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, 0);
	if (ret == -ENOTBLK)
		ret = 0;
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)
{
	struct gfs2_inode *ip;
	struct gfs2_holder gh;
	size_t written = 0;
	ssize_t ret;

	if (iocb->ki_flags & IOCB_DIRECT) {
		ret = gfs2_file_direct_read(iocb, to, &gh);
		if (likely(ret != -ENOTBLK))
			return ret;
		iocb->ki_flags &= ~IOCB_DIRECT;
	}
	iocb->ki_flags |= IOCB_NOIO;
	ret = generic_file_read_iter(iocb, to);
	iocb->ki_flags &= ~IOCB_NOIO;
	if (ret >= 0) {
		if (!iov_iter_count(to))
			return ret;
		written = ret;
	} else {
		if (ret != -EAGAIN)
			return ret;
		if (iocb->ki_flags & IOCB_NOWAIT)
			return ret;
	}
	ip = GFS2_I(iocb->ki_filp->f_mapping->host);
	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
	ret = gfs2_glock_nq(&gh);
	if (ret)
		goto out_uninit;
	ret = generic_file_read_iter(iocb, to);
	if (ret > 0)
		written += ret;
	gfs2_glock_dq(&gh);
out_uninit:
	gfs2_holder_uninit(&gh);
	return written ? written : ret;
}

/**
 * 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);
	struct gfs2_holder gh;
	ssize_t ret;

	gfs2_size_hint(file, iocb->ki_pos, iov_iter_count(from));

	if (iocb->ki_flags & IOCB_APPEND) {
		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_unlock;

	ret = file_remove_privs(file);
	if (ret)
		goto out_unlock;

	ret = file_update_time(file);
	if (ret)
		goto out_unlock;

	if (iocb->ki_flags & IOCB_DIRECT) {
		struct address_space *mapping = file->f_mapping;
		ssize_t buffered, ret2;

		ret = gfs2_file_direct_write(iocb, from, &gh);
		if (ret < 0 || !iov_iter_count(from))
			goto out_unlock;

		iocb->ki_flags |= IOCB_DSYNC;
		current->backing_dev_info = inode_to_bdi(inode);
		buffered = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
		current->backing_dev_info = NULL;
		if (unlikely(buffered <= 0)) {
			if (!ret)
				ret = buffered;
			goto out_unlock;
		}

		/*
		 * We need to ensure that the page cache pages are written to
		 * disk and invalidated to preserve the expected O_DIRECT
		 * semantics.  If the writeback or invalidate fails, only report
		 * the direct I/O range as we don't know if the buffered pages
		 * made it to disk.
		 */
		iocb->ki_pos += buffered;
		ret2 = generic_write_sync(iocb, buffered);
		invalidate_mapping_pages(mapping,
				(iocb->ki_pos - buffered) >> PAGE_SHIFT,
				(iocb->ki_pos - 1) >> PAGE_SHIFT);
		if (!ret || ret2 > 0)
			ret += ret2;
	} else {
		current->backing_dev_info = inode_to_bdi(inode);
		ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
		current->backing_dev_info = NULL;
		if (likely(ret > 0)) {
			iocb->ki_pos += ret;
			ret = generic_write_sync(iocb, ret);
		}
	}

out_unlock:
	inode_unlock(inode);
	return 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);
		if (unlikely(error))
			goto out;
	}

	while (offset < end) {
		struct iomap iomap = { };

		error = gfs2_iomap_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 (ip->i_res.rs_reserved < max_blks)
			max_blks = ip->i_res.rs_reserved;

		/* 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 >> inode->i_blkbits);
		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_fallocate(file, mode, offset, len);
		if (ret)
			gfs2_rs_deltree(&ip->i_res);
	}

	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)
{
	ssize_t ret;

	gfs2_size_hint(out, *ppos, len);

	ret = iter_file_splice_write(pipe, out, ppos, len, flags);
	return ret;
}

#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 (cmd == F_CANCELLK) {
		/* Hack: */
		cmd = F_SETLK;
		fl->fl_type = F_UNLCK;
	}
	if (unlikely(gfs2_withdrawn(sdp))) {
		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,
	.compat_ioctl	= gfs2_compat_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,
	.compat_ioctl	= gfs2_compat_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,
	.compat_ioctl	= gfs2_compat_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,
	.compat_ioctl	= gfs2_compat_ioctl,
	.open		= gfs2_open,
	.release	= gfs2_release,
	.fsync		= gfs2_fsync,
	.llseek		= default_llseek,
};