// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_inode_item.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_error.h"
#include "xfs_dir2.h"
#include "xfs_dir2_priv.h"
#include "xfs_ioctl.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_icache.h"
#include "xfs_pnfs.h"
#include "xfs_iomap.h"
#include "xfs_reflink.h"

#include <linux/dcache.h>
#include <linux/falloc.h>
#include <linux/pagevec.h>
#include <linux/backing-dev.h>
#include <linux/mman.h>

static const struct vm_operations_struct xfs_file_vm_ops;

int
xfs_update_prealloc_flags(
        struct xfs_inode        *ip,
        enum xfs_prealloc_flags flags)
{
        struct xfs_trans        *tp;
        int                     error;

        error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_writeid,
                        0, 0, 0, &tp);
        if (error)
                return error;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);

        if (!(flags & XFS_PREALLOC_INVISIBLE)) {
                VFS_I(ip)->i_mode &= ~S_ISUID;
                if (VFS_I(ip)->i_mode & S_IXGRP)
                        VFS_I(ip)->i_mode &= ~S_ISGID;
                xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
        }

        if (flags & XFS_PREALLOC_SET)
                ip->i_d.di_flags |= XFS_DIFLAG_PREALLOC;
        if (flags & XFS_PREALLOC_CLEAR)
                ip->i_d.di_flags &= ~XFS_DIFLAG_PREALLOC;

        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
        if (flags & XFS_PREALLOC_SYNC)
                xfs_trans_set_sync(tp);
        return xfs_trans_commit(tp);
}

/*
 * Fsync operations on directories are much simpler than on regular files,
 * as there is no file data to flush, and thus also no need for explicit
 * cache flush operations, and there are no non-transaction metadata updates
 * on directories either.
 */
STATIC int
xfs_dir_fsync(
        struct file             *file,
        loff_t                  start,
        loff_t                  end,
        int                     datasync)
{
        struct xfs_inode        *ip = XFS_I(file->f_mapping->host);
        struct xfs_mount        *mp = ip->i_mount;
        xfs_lsn_t               lsn = 0;

        trace_xfs_dir_fsync(ip);

        xfs_ilock(ip, XFS_ILOCK_SHARED);
        if (xfs_ipincount(ip))
                lsn = ip->i_itemp->ili_last_lsn;
        xfs_iunlock(ip, XFS_ILOCK_SHARED);

        if (!lsn)
                return 0;
        return xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, NULL);
}

STATIC int
xfs_file_fsync(
        struct file             *file,
        loff_t                  start,
        loff_t                  end,
        int                     datasync)
{
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        int                     error = 0;
        int                     log_flushed = 0;
        xfs_lsn_t               lsn = 0;

        trace_xfs_file_fsync(ip);

        error = file_write_and_wait_range(file, start, end);
        if (error)
                return error;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        xfs_iflags_clear(ip, XFS_ITRUNCATED);

        /*
         * If we have an RT and/or log subvolume we need to make sure to flush
         * the write cache the device used for file data first.  This is to
         * ensure newly written file data make it to disk before logging the new
         * inode size in case of an extending write.
         */
        if (XFS_IS_REALTIME_INODE(ip))
                xfs_blkdev_issue_flush(mp->m_rtdev_targp);
        else if (mp->m_logdev_targp != mp->m_ddev_targp)
                xfs_blkdev_issue_flush(mp->m_ddev_targp);

        /*
         * All metadata updates are logged, which means that we just have to
         * flush the log up to the latest LSN that touched the inode. If we have
         * concurrent fsync/fdatasync() calls, we need them to all block on the
         * log force before we clear the ili_fsync_fields field. This ensures
         * that we don't get a racing sync operation that does not wait for the
         * metadata to hit the journal before returning. If we race with
         * clearing the ili_fsync_fields, then all that will happen is the log
         * force will do nothing as the lsn will already be on disk. We can't
         * race with setting ili_fsync_fields because that is done under
         * XFS_ILOCK_EXCL, and that can't happen because we hold the lock shared
         * until after the ili_fsync_fields is cleared.
         */
        xfs_ilock(ip, XFS_ILOCK_SHARED);
        if (xfs_ipincount(ip)) {
                if (!datasync ||
                    (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
                        lsn = ip->i_itemp->ili_last_lsn;
        }

        if (lsn) {
                error = xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, &log_flushed);
                ip->i_itemp->ili_fsync_fields = 0;
        }
        xfs_iunlock(ip, XFS_ILOCK_SHARED);

        /*
         * If we only have a single device, and the log force about was
         * a no-op we might have to flush the data device cache here.
         * This can only happen for fdatasync/O_DSYNC if we were overwriting
         * an already allocated file and thus do not have any metadata to
         * commit.
         */
        if (!log_flushed && !XFS_IS_REALTIME_INODE(ip) &&
            mp->m_logdev_targp == mp->m_ddev_targp)
                xfs_blkdev_issue_flush(mp->m_ddev_targp);

        return error;
}

STATIC ssize_t
xfs_file_dio_aio_read(
        struct kiocb            *iocb,
        struct iov_iter         *to)
{
        struct xfs_inode        *ip = XFS_I(file_inode(iocb->ki_filp));
        size_t                  count = iov_iter_count(to);
        ssize_t                 ret;

        trace_xfs_file_direct_read(ip, count, iocb->ki_pos);

        if (!count)
                return 0; /* skip atime */

        file_accessed(iocb->ki_filp);

        xfs_ilock(ip, XFS_IOLOCK_SHARED);
        ret = iomap_dio_rw(iocb, to, &xfs_iomap_ops, NULL);
        xfs_iunlock(ip, XFS_IOLOCK_SHARED);

        return ret;
}

static noinline ssize_t
xfs_file_dax_read(
        struct kiocb            *iocb,
        struct iov_iter         *to)
{
        struct xfs_inode        *ip = XFS_I(iocb->ki_filp->f_mapping->host);
        size_t                  count = iov_iter_count(to);
        ssize_t                 ret = 0;

        trace_xfs_file_dax_read(ip, count, iocb->ki_pos);

        if (!count)
                return 0; /* skip atime */

        if (iocb->ki_flags & IOCB_NOWAIT) {
                if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
                        return -EAGAIN;
        } else {
                xfs_ilock(ip, XFS_IOLOCK_SHARED);
        }

        ret = dax_iomap_rw(iocb, to, &xfs_iomap_ops);
        xfs_iunlock(ip, XFS_IOLOCK_SHARED);

        file_accessed(iocb->ki_filp);
        return ret;
}

STATIC ssize_t
xfs_file_buffered_aio_read(
        struct kiocb            *iocb,
        struct iov_iter         *to)
{
        struct xfs_inode        *ip = XFS_I(file_inode(iocb->ki_filp));
        ssize_t                 ret;

        trace_xfs_file_buffered_read(ip, iov_iter_count(to), iocb->ki_pos);

        if (iocb->ki_flags & IOCB_NOWAIT) {
                if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
                        return -EAGAIN;
        } else {
                xfs_ilock(ip, XFS_IOLOCK_SHARED);
        }
        ret = generic_file_read_iter(iocb, to);
        xfs_iunlock(ip, XFS_IOLOCK_SHARED);

        return ret;
}

STATIC ssize_t
xfs_file_read_iter(
        struct kiocb            *iocb,
        struct iov_iter         *to)
{
        struct inode            *inode = file_inode(iocb->ki_filp);
        struct xfs_mount        *mp = XFS_I(inode)->i_mount;
        ssize_t                 ret = 0;

        XFS_STATS_INC(mp, xs_read_calls);

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        if (IS_DAX(inode))
                ret = xfs_file_dax_read(iocb, to);
        else if (iocb->ki_flags & IOCB_DIRECT)
                ret = xfs_file_dio_aio_read(iocb, to);
        else
                ret = xfs_file_buffered_aio_read(iocb, to);

        if (ret > 0)
                XFS_STATS_ADD(mp, xs_read_bytes, ret);
        return ret;
}

/*
 * Common pre-write limit and setup checks.
 *
 * Called with the iolocked held either shared and exclusive according to
 * @iolock, and returns with it held.  Might upgrade the iolock to exclusive
 * if called for a direct write beyond i_size.
 */
STATIC ssize_t
xfs_file_aio_write_checks(
        struct kiocb            *iocb,
        struct iov_iter         *from,
        int                     *iolock)
{
        struct file             *file = iocb->ki_filp;
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        ssize_t                 error = 0;
        size_t                  count = iov_iter_count(from);
        bool                    drained_dio = false;
        loff_t                  isize;

restart:
        error = generic_write_checks(iocb, from);
        if (error <= 0)
                return error;

        error = xfs_break_layouts(inode, iolock, BREAK_WRITE);
        if (error)
                return error;

        /*
         * For changing security info in file_remove_privs() we need i_rwsem
         * exclusively.
         */
        if (*iolock == XFS_IOLOCK_SHARED && !IS_NOSEC(inode)) {
                xfs_iunlock(ip, *iolock);
                *iolock = XFS_IOLOCK_EXCL;
                xfs_ilock(ip, *iolock);
                goto restart;
        }
        /*
         * If the offset is beyond the size of the file, we need to zero any
         * blocks that fall between the existing EOF and the start of this
         * write.  If zeroing is needed and we are currently holding the
         * iolock shared, we need to update it to exclusive which implies
         * having to redo all checks before.
         *
         * We need to serialise against EOF updates that occur in IO
         * completions here. We want to make sure that nobody is changing the
         * size while we do this check until we have placed an IO barrier (i.e.
         * hold the XFS_IOLOCK_EXCL) that prevents new IO from being dispatched.
         * The spinlock effectively forms a memory barrier once we have the
         * XFS_IOLOCK_EXCL so we are guaranteed to see the latest EOF value
         * and hence be able to correctly determine if we need to run zeroing.
         */
        spin_lock(&ip->i_flags_lock);
        isize = i_size_read(inode);
        if (iocb->ki_pos > isize) {
                spin_unlock(&ip->i_flags_lock);
                if (!drained_dio) {
                        if (*iolock == XFS_IOLOCK_SHARED) {
                                xfs_iunlock(ip, *iolock);
                                *iolock = XFS_IOLOCK_EXCL;
                                xfs_ilock(ip, *iolock);
                                iov_iter_reexpand(from, count);
                        }
                        /*
                         * We now have an IO submission barrier in place, but
                         * AIO can do EOF updates during IO completion and hence
                         * we now need to wait for all of them to drain. Non-AIO
                         * DIO will have drained before we are given the
                         * XFS_IOLOCK_EXCL, and so for most cases this wait is a
                         * no-op.
                         */
                        inode_dio_wait(inode);
                        drained_dio = true;
                        goto restart;
                }
        
                trace_xfs_zero_eof(ip, isize, iocb->ki_pos - isize);
                error = iomap_zero_range(inode, isize, iocb->ki_pos - isize,
                                NULL, &xfs_iomap_ops);
                if (error)
                        return error;
        } else
                spin_unlock(&ip->i_flags_lock);

        /*
         * Updating the timestamps will grab the ilock again from
         * xfs_fs_dirty_inode, so we have to call it after dropping the
         * lock above.  Eventually we should look into a way to avoid
         * the pointless lock roundtrip.
         */
        if (likely(!(file->f_mode & FMODE_NOCMTIME))) {
                error = file_update_time(file);
                if (error)
                        return error;
        }

        /*
         * If we're writing the file then make sure to clear the setuid and
         * setgid bits if the process is not being run by root.  This keeps
         * people from modifying setuid and setgid binaries.
         */
        if (!IS_NOSEC(inode))
                return file_remove_privs(file);
        return 0;
}

static int
xfs_dio_write_end_io(
        struct kiocb            *iocb,
        ssize_t                 size,
        unsigned                flags)
{
        struct inode            *inode = file_inode(iocb->ki_filp);
        struct xfs_inode        *ip = XFS_I(inode);
        loff_t                  offset = iocb->ki_pos;
        int                     error = 0;

        trace_xfs_end_io_direct_write(ip, offset, size);

        if (XFS_FORCED_SHUTDOWN(ip->i_mount))
                return -EIO;

        if (size <= 0)
                return size;

        /*
         * Capture amount written on completion as we can't reliably account
         * for it on submission.
         */
        XFS_STATS_ADD(ip->i_mount, xs_write_bytes, size);

        if (flags & IOMAP_DIO_COW) {
                error = xfs_reflink_end_cow(ip, offset, size);
                if (error)
                        return error;
        }

        /*
         * Unwritten conversion updates the in-core isize after extent
         * conversion but before updating the on-disk size. Updating isize any
         * earlier allows a racing dio read to find unwritten extents before
         * they are converted.
         */
        if (flags & IOMAP_DIO_UNWRITTEN)
                return xfs_iomap_write_unwritten(ip, offset, size, true);

        /*
         * We need to update the in-core inode size here so that we don't end up
         * with the on-disk inode size being outside the in-core inode size. We
         * have no other method of updating EOF for AIO, so always do it here
         * if necessary.
         *
         * We need to lock the test/set EOF update as we can be racing with
         * other IO completions here to update the EOF. Failing to serialise
         * here can result in EOF moving backwards and Bad Things Happen when
         * that occurs.
         */
        spin_lock(&ip->i_flags_lock);
        if (offset + size > i_size_read(inode)) {
                i_size_write(inode, offset + size);
                spin_unlock(&ip->i_flags_lock);
                error = xfs_setfilesize(ip, offset, size);
        } else {
                spin_unlock(&ip->i_flags_lock);
        }

        return error;
}

/*
 * xfs_file_dio_aio_write - handle direct IO writes
 *
 * Lock the inode appropriately to prepare for and issue a direct IO write.
 * By separating it from the buffered write path we remove all the tricky to
 * follow locking changes and looping.
 *
 * If there are cached pages or we're extending the file, we need IOLOCK_EXCL
 * until we're sure the bytes at the new EOF have been zeroed and/or the cached
 * pages are flushed out.
 *
 * In most cases the direct IO writes will be done holding IOLOCK_SHARED
 * allowing them to be done in parallel with reads and other direct IO writes.
 * However, if the IO is not aligned to filesystem blocks, the direct IO layer
 * needs to do sub-block zeroing and that requires serialisation against other
 * direct IOs to the same block. In this case we need to serialise the
 * submission of the unaligned IOs so that we don't get racing block zeroing in
 * the dio layer.  To avoid the problem with aio, we also need to wait for
 * outstanding IOs to complete so that unwritten extent conversion is completed
 * before we try to map the overlapping block. This is currently implemented by
 * hitting it with a big hammer (i.e. inode_dio_wait()).
 *
 * Returns with locks held indicated by @iolock and errors indicated by
 * negative return values.
 */
STATIC ssize_t
xfs_file_dio_aio_write(
        struct kiocb            *iocb,
        struct iov_iter         *from)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        ssize_t                 ret = 0;
        int                     unaligned_io = 0;
        int                     iolock;
        size_t                  count = iov_iter_count(from);
        struct xfs_buftarg      *target = XFS_IS_REALTIME_INODE(ip) ?
                                        mp->m_rtdev_targp : mp->m_ddev_targp;

        /* DIO must be aligned to device logical sector size */
        if ((iocb->ki_pos | count) & target->bt_logical_sectormask)
                return -EINVAL;

        /*
         * Don't take the exclusive iolock here unless the I/O is unaligned to
         * the file system block size.  We don't need to consider the EOF
         * extension case here because xfs_file_aio_write_checks() will relock
         * the inode as necessary for EOF zeroing cases and fill out the new
         * inode size as appropriate.
         */
        if ((iocb->ki_pos & mp->m_blockmask) ||
            ((iocb->ki_pos + count) & mp->m_blockmask)) {
                unaligned_io = 1;

                /*
                 * We can't properly handle unaligned direct I/O to reflink
                 * files yet, as we can't unshare a partial block.
                 */
                if (xfs_is_cow_inode(ip)) {
                        trace_xfs_reflink_bounce_dio_write(ip, iocb->ki_pos, count);
                        return -EREMCHG;
                }
                iolock = XFS_IOLOCK_EXCL;
        } else {
                iolock = XFS_IOLOCK_SHARED;
        }

        if (iocb->ki_flags & IOCB_NOWAIT) {
                if (!xfs_ilock_nowait(ip, iolock))
                        return -EAGAIN;
        } else {
                xfs_ilock(ip, iolock);
        }

        ret = xfs_file_aio_write_checks(iocb, from, &iolock);
        if (ret)
                goto out;
        count = iov_iter_count(from);

        /*
         * If we are doing unaligned IO, we can't allow any other overlapping IO
         * in-flight at the same time or we risk data corruption. Wait for all
         * other IO to drain before we submit. If the IO is aligned, demote the
         * iolock if we had to take the exclusive lock in
         * xfs_file_aio_write_checks() for other reasons.
         */
        if (unaligned_io) {
                /* unaligned dio always waits, bail */
                if (iocb->ki_flags & IOCB_NOWAIT)
                        return -EAGAIN;
                inode_dio_wait(inode);
        } else if (iolock == XFS_IOLOCK_EXCL) {
                xfs_ilock_demote(ip, XFS_IOLOCK_EXCL);
                iolock = XFS_IOLOCK_SHARED;
        }

        trace_xfs_file_direct_write(ip, count, iocb->ki_pos);
        ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, xfs_dio_write_end_io);

        /*
         * If unaligned, this is the only IO in-flight. If it has not yet
         * completed, wait on it before we release the iolock to prevent
         * subsequent overlapping IO.
         */
        if (ret == -EIOCBQUEUED && unaligned_io)
                inode_dio_wait(inode);
out:
        xfs_iunlock(ip, iolock);

        /*
         * No fallback to buffered IO on errors for XFS, direct IO will either
         * complete fully or fail.
         */
        ASSERT(ret < 0 || ret == count);
        return ret;
}

static noinline ssize_t
xfs_file_dax_write(
        struct kiocb            *iocb,
        struct iov_iter         *from)
{
        struct inode            *inode = iocb->ki_filp->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        int                     iolock = XFS_IOLOCK_EXCL;
        ssize_t                 ret, error = 0;
        size_t                  count;
        loff_t                  pos;

        if (iocb->ki_flags & IOCB_NOWAIT) {
                if (!xfs_ilock_nowait(ip, iolock))
                        return -EAGAIN;
        } else {
                xfs_ilock(ip, iolock);
        }

        ret = xfs_file_aio_write_checks(iocb, from, &iolock);
        if (ret)
                goto out;

        pos = iocb->ki_pos;
        count = iov_iter_count(from);

        trace_xfs_file_dax_write(ip, count, pos);
        ret = dax_iomap_rw(iocb, from, &xfs_iomap_ops);
        if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
                i_size_write(inode, iocb->ki_pos);
                error = xfs_setfilesize(ip, pos, ret);
        }
out:
        xfs_iunlock(ip, iolock);
        if (error)
                return error;

        if (ret > 0) {
                XFS_STATS_ADD(ip->i_mount, xs_write_bytes, ret);

                /* Handle various SYNC-type writes */
                ret = generic_write_sync(iocb, ret);
        }
        return ret;
}

STATIC ssize_t
xfs_file_buffered_aio_write(
        struct kiocb            *iocb,
        struct iov_iter         *from)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        ssize_t                 ret;
        int                     enospc = 0;
        int                     iolock;

        if (iocb->ki_flags & IOCB_NOWAIT)
                return -EOPNOTSUPP;

write_retry:
        iolock = XFS_IOLOCK_EXCL;
        xfs_ilock(ip, iolock);

        ret = xfs_file_aio_write_checks(iocb, from, &iolock);
        if (ret)
                goto out;

        /* We can write back this queue in page reclaim */
        current->backing_dev_info = inode_to_bdi(inode);

        trace_xfs_file_buffered_write(ip, iov_iter_count(from), iocb->ki_pos);
        ret = iomap_file_buffered_write(iocb, from, &xfs_iomap_ops);
        if (likely(ret >= 0))
                iocb->ki_pos += ret;

        /*
         * If we hit a space limit, try to free up some lingering preallocated
         * space before returning an error. In the case of ENOSPC, first try to
         * write back all dirty inodes to free up some of the excess reserved
         * metadata space. This reduces the chances that the eofblocks scan
         * waits on dirty mappings. Since xfs_flush_inodes() is serialized, this
         * also behaves as a filter to prevent too many eofblocks scans from
         * running at the same time.
         */
        if (ret == -EDQUOT && !enospc) {
                xfs_iunlock(ip, iolock);
                enospc = xfs_inode_free_quota_eofblocks(ip);
                if (enospc)
                        goto write_retry;
                enospc = xfs_inode_free_quota_cowblocks(ip);
                if (enospc)
                        goto write_retry;
                iolock = 0;
        } else if (ret == -ENOSPC && !enospc) {
                struct xfs_eofblocks eofb = {0};

                enospc = 1;
                xfs_flush_inodes(ip->i_mount);

                xfs_iunlock(ip, iolock);
                eofb.eof_flags = XFS_EOF_FLAGS_SYNC;
                xfs_icache_free_eofblocks(ip->i_mount, &eofb);
                xfs_icache_free_cowblocks(ip->i_mount, &eofb);
                goto write_retry;
        }

        current->backing_dev_info = NULL;
out:
        if (iolock)
                xfs_iunlock(ip, iolock);

        if (ret > 0) {
                XFS_STATS_ADD(ip->i_mount, xs_write_bytes, ret);
                /* Handle various SYNC-type writes */
                ret = generic_write_sync(iocb, ret);
        }
        return ret;
}

STATIC ssize_t
xfs_file_write_iter(
        struct kiocb            *iocb,
        struct iov_iter         *from)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        ssize_t                 ret;
        size_t                  ocount = iov_iter_count(from);

        XFS_STATS_INC(ip->i_mount, xs_write_calls);

        if (ocount == 0)
                return 0;

        if (XFS_FORCED_SHUTDOWN(ip->i_mount))
                return -EIO;

        if (IS_DAX(inode))
                return xfs_file_dax_write(iocb, from);

        if (iocb->ki_flags & IOCB_DIRECT) {
                /*
                 * Allow a directio write to fall back to a buffered
                 * write *only* in the case that we're doing a reflink
                 * CoW.  In all other directio scenarios we do not
                 * allow an operation to fall back to buffered mode.
                 */
                ret = xfs_file_dio_aio_write(iocb, from);
                if (ret != -EREMCHG)
                        return ret;
        }

        return xfs_file_buffered_aio_write(iocb, from);
}

static void
xfs_wait_dax_page(
        struct inode            *inode)
{
        struct xfs_inode        *ip = XFS_I(inode);

        xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
        schedule();
        xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
}

static int
xfs_break_dax_layouts(
        struct inode            *inode,
        bool                    *retry)
{
        struct page             *page;

        ASSERT(xfs_isilocked(XFS_I(inode), XFS_MMAPLOCK_EXCL));

        page = dax_layout_busy_page(inode->i_mapping);
        if (!page)
                return 0;

        *retry = true;
        return ___wait_var_event(&page->_refcount,
                        atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
                        0, 0, xfs_wait_dax_page(inode));
}

int
xfs_break_layouts(
        struct inode            *inode,
        uint                    *iolock,
        enum layout_break_reason reason)
{
        bool                    retry;
        int                     error;

        ASSERT(xfs_isilocked(XFS_I(inode), XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL));

        do {
                retry = false;
                switch (reason) {
                case BREAK_UNMAP:
                        error = xfs_break_dax_layouts(inode, &retry);
                        if (error || retry)
                                break;
                        /* fall through */
                case BREAK_WRITE:
                        error = xfs_break_leased_layouts(inode, iolock, &retry);
                        break;
                default:
                        WARN_ON_ONCE(1);
                        error = -EINVAL;
                }
        } while (error == 0 && retry);

        return error;
}

#define XFS_FALLOC_FL_SUPPORTED                                         \
                (FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |           \
                 FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |      \
                 FALLOC_FL_INSERT_RANGE | FALLOC_FL_UNSHARE_RANGE)

STATIC long
xfs_file_fallocate(
        struct file             *file,
        int                     mode,
        loff_t                  offset,
        loff_t                  len)
{
        struct inode            *inode = file_inode(file);
        struct xfs_inode        *ip = XFS_I(inode);
        long                    error;
        enum xfs_prealloc_flags flags = 0;
        uint                    iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
        loff_t                  new_size = 0;
        bool                    do_file_insert = false;

        if (!S_ISREG(inode->i_mode))
                return -EINVAL;
        if (mode & ~XFS_FALLOC_FL_SUPPORTED)
                return -EOPNOTSUPP;

        xfs_ilock(ip, iolock);
        error = xfs_break_layouts(inode, &iolock, BREAK_UNMAP);
        if (error)
                goto out_unlock;

        if (mode & FALLOC_FL_PUNCH_HOLE) {
                error = xfs_free_file_space(ip, offset, len);
                if (error)
                        goto out_unlock;
        } else if (mode & FALLOC_FL_COLLAPSE_RANGE) {
                unsigned int blksize_mask = i_blocksize(inode) - 1;

                if (offset & blksize_mask || len & blksize_mask) {
                        error = -EINVAL;
                        goto out_unlock;
                }

                /*
                 * There is no need to overlap collapse range with EOF,
                 * in which case it is effectively a truncate operation
                 */
                if (offset + len >= i_size_read(inode)) {
                        error = -EINVAL;
                        goto out_unlock;
                }

                new_size = i_size_read(inode) - len;

                error = xfs_collapse_file_space(ip, offset, len);
                if (error)
                        goto out_unlock;
        } else if (mode & FALLOC_FL_INSERT_RANGE) {
                unsigned int    blksize_mask = i_blocksize(inode) - 1;
                loff_t          isize = i_size_read(inode);

                if (offset & blksize_mask || len & blksize_mask) {
                        error = -EINVAL;
                        goto out_unlock;
                }

                /*
                 * New inode size must not exceed ->s_maxbytes, accounting for
                 * possible signed overflow.
                 */
                if (inode->i_sb->s_maxbytes - isize < len) {
                        error = -EFBIG;
                        goto out_unlock;
                }
                new_size = isize + len;

                /* Offset should be less than i_size */
                if (offset >= isize) {
                        error = -EINVAL;
                        goto out_unlock;
                }
                do_file_insert = true;
        } else {
                flags |= XFS_PREALLOC_SET;

                if (!(mode & FALLOC_FL_KEEP_SIZE) &&
                    offset + len > i_size_read(inode)) {
                        new_size = offset + len;
                        error = inode_newsize_ok(inode, new_size);
                        if (error)
                                goto out_unlock;
                }

                if (mode & FALLOC_FL_ZERO_RANGE) {
                        error = xfs_zero_file_space(ip, offset, len);
                } else if (mode & FALLOC_FL_UNSHARE_RANGE) {
                        error = xfs_reflink_unshare(ip, offset, len);
                        if (error)
                                goto out_unlock;

                        if (!xfs_is_always_cow_inode(ip)) {
                                error = xfs_alloc_file_space(ip, offset, len,
                                                XFS_BMAPI_PREALLOC);
                        }
                } else {
                        /*
                         * If always_cow mode we can't use preallocations and
                         * thus should not create them.
                         */
                        if (xfs_is_always_cow_inode(ip)) {
                                error = -EOPNOTSUPP;
                                goto out_unlock;
                        }

                        error = xfs_alloc_file_space(ip, offset, len,
                                                     XFS_BMAPI_PREALLOC);
                }
                if (error)
                        goto out_unlock;
        }

        if (file->f_flags & O_DSYNC)
                flags |= XFS_PREALLOC_SYNC;

        error = xfs_update_prealloc_flags(ip, flags);
        if (error)
                goto out_unlock;

        /* Change file size if needed */
        if (new_size) {
                struct iattr iattr;

                iattr.ia_valid = ATTR_SIZE;
                iattr.ia_size = new_size;
                error = xfs_vn_setattr_size(file_dentry(file), &iattr);
                if (error)
                        goto out_unlock;
        }

        /*
         * Perform hole insertion now that the file size has been
         * updated so that if we crash during the operation we don't
         * leave shifted extents past EOF and hence losing access to
         * the data that is contained within them.
         */
        if (do_file_insert)
                error = xfs_insert_file_space(ip, offset, len);

out_unlock:
        xfs_iunlock(ip, iolock);
        return error;
}


STATIC loff_t
xfs_file_remap_range(
        struct file             *file_in,
        loff_t                  pos_in,
        struct file             *file_out,
        loff_t                  pos_out,
        loff_t                  len,
        unsigned int            remap_flags)
{
        struct inode            *inode_in = file_inode(file_in);
        struct xfs_inode        *src = XFS_I(inode_in);
        struct inode            *inode_out = file_inode(file_out);
        struct xfs_inode        *dest = XFS_I(inode_out);
        struct xfs_mount        *mp = src->i_mount;
        loff_t                  remapped = 0;
        xfs_extlen_t            cowextsize;
        int                     ret;

        if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
                return -EINVAL;

        if (!xfs_sb_version_hasreflink(&mp->m_sb))
                return -EOPNOTSUPP;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        /* Prepare and then clone file data. */
        ret = xfs_reflink_remap_prep(file_in, pos_in, file_out, pos_out,
                        &len, remap_flags);
        if (ret < 0 || len == 0)
                return ret;

        trace_xfs_reflink_remap_range(src, pos_in, len, dest, pos_out);

        ret = xfs_reflink_remap_blocks(src, pos_in, dest, pos_out, len,
                        &remapped);
        if (ret)
                goto out_unlock;

        /*
         * Carry the cowextsize hint from src to dest if we're sharing the
         * entire source file to the entire destination file, the source file
         * has a cowextsize hint, and the destination file does not.
         */
        cowextsize = 0;
        if (pos_in == 0 && len == i_size_read(inode_in) &&
            (src->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE) &&
            pos_out == 0 && len >= i_size_read(inode_out) &&
            !(dest->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE))
                cowextsize = src->i_d.di_cowextsize;

        ret = xfs_reflink_update_dest(dest, pos_out + len, cowextsize,
                        remap_flags);

out_unlock:
        xfs_reflink_remap_unlock(file_in, file_out);
        if (ret)

                trace_xfs_reflink_remap_range_error(dest, ret, _RET_IP_);
        return remapped > 0 ? remapped : ret;
}

STATIC int
xfs_file_open(
        struct inode    *inode,
        struct file     *file)
{
        if (!(file->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
                return -EFBIG;
        if (XFS_FORCED_SHUTDOWN(XFS_M(inode->i_sb)))
                return -EIO;
        file->f_mode |= FMODE_NOWAIT;
        return 0;
}

STATIC int
xfs_dir_open(
        struct inode    *inode,
        struct file     *file)
{
        struct xfs_inode *ip = XFS_I(inode);
        int             mode;
        int             error;

        error = xfs_file_open(inode, file);
        if (error)
                return error;

        /*
         * If there are any blocks, read-ahead block 0 as we're almost
         * certain to have the next operation be a read there.
         */
        mode = xfs_ilock_data_map_shared(ip);
        if (ip->i_d.di_nextents > 0)
                error = xfs_dir3_data_readahead(ip, 0, -1);
        xfs_iunlock(ip, mode);
        return error;
}

STATIC int
xfs_file_release(
        struct inode    *inode,
        struct file     *filp)
{
        return xfs_release(XFS_I(inode));
}

STATIC int
xfs_file_readdir(
        struct file     *file,
        struct dir_context *ctx)
{
        struct inode    *inode = file_inode(file);
        xfs_inode_t     *ip = XFS_I(inode);
        size_t          bufsize;

        /*
         * The Linux API doesn't pass down the total size of the buffer
         * we read into down to the filesystem.  With the filldir concept
         * it's not needed for correct information, but the XFS dir2 leaf
         * code wants an estimate of the buffer size to calculate it's
         * readahead window and size the buffers used for mapping to
         * physical blocks.
         *
         * Try to give it an estimate that's good enough, maybe at some
         * point we can change the ->readdir prototype to include the
         * buffer size.  For now we use the current glibc buffer size.
         */
        bufsize = (size_t)min_t(loff_t, XFS_READDIR_BUFSIZE, ip->i_d.di_size);

        return xfs_readdir(NULL, ip, ctx, bufsize);
}

STATIC loff_t
xfs_file_llseek(
        struct file     *file,
        loff_t          offset,
        int             whence)
{
        struct inode            *inode = file->f_mapping->host;

        if (XFS_FORCED_SHUTDOWN(XFS_I(inode)->i_mount))
                return -EIO;

        switch (whence) {
        default:
                return generic_file_llseek(file, offset, whence);
        case SEEK_HOLE:
                offset = iomap_seek_hole(inode, offset, &xfs_seek_iomap_ops);
                break;
        case SEEK_DATA:
                offset = iomap_seek_data(inode, offset, &xfs_seek_iomap_ops);
                break;
        }

        if (offset < 0)
                return offset;
        return vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
}

/*
 * Locking for serialisation of IO during page faults. This results in a lock
 * ordering of:
 *
 * mmap_sem (MM)
 *   sb_start_pagefault(vfs, freeze)
 *     i_mmaplock (XFS - truncate serialisation)
 *       page_lock (MM)
 *         i_lock (XFS - extent map serialisation)
 */
static vm_fault_t
__xfs_filemap_fault(
        struct vm_fault         *vmf,
        enum page_entry_size    pe_size,
        bool                    write_fault)
{
        struct inode            *inode = file_inode(vmf->vma->vm_file);
        struct xfs_inode        *ip = XFS_I(inode);
        vm_fault_t              ret;

        trace_xfs_filemap_fault(ip, pe_size, write_fault);

        if (write_fault) {
                sb_start_pagefault(inode->i_sb);
                file_update_time(vmf->vma->vm_file);
        }

        xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
        if (IS_DAX(inode)) {
                pfn_t pfn;

                ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL, &xfs_iomap_ops);
                if (ret & VM_FAULT_NEEDDSYNC)
                        ret = dax_finish_sync_fault(vmf, pe_size, pfn);
        } else {
                if (write_fault)
                        ret = iomap_page_mkwrite(vmf, &xfs_iomap_ops);
                else
                        ret = filemap_fault(vmf);
        }
        xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);

        if (write_fault)
                sb_end_pagefault(inode->i_sb);
        return ret;
}

static vm_fault_t
xfs_filemap_fault(
        struct vm_fault         *vmf)
{
        /* DAX can shortcut the normal fault path on write faults! */
        return __xfs_filemap_fault(vmf, PE_SIZE_PTE,
                        IS_DAX(file_inode(vmf->vma->vm_file)) &&
                        (vmf->flags & FAULT_FLAG_WRITE));
}

static vm_fault_t
xfs_filemap_huge_fault(
        struct vm_fault         *vmf,
        enum page_entry_size    pe_size)
{
        if (!IS_DAX(file_inode(vmf->vma->vm_file)))
                return VM_FAULT_FALLBACK;

        /* DAX can shortcut the normal fault path on write faults! */
        return __xfs_filemap_fault(vmf, pe_size,
                        (vmf->flags & FAULT_FLAG_WRITE));
}

static vm_fault_t
xfs_filemap_page_mkwrite(
        struct vm_fault         *vmf)
{
        return __xfs_filemap_fault(vmf, PE_SIZE_PTE, true);
}

/*
 * pfn_mkwrite was originally intended to ensure we capture time stamp updates
 * on write faults. In reality, it needs to serialise against truncate and
 * prepare memory for writing so handle is as standard write fault.
 */
static vm_fault_t
xfs_filemap_pfn_mkwrite(
        struct vm_fault         *vmf)
{

        return __xfs_filemap_fault(vmf, PE_SIZE_PTE, true);
}

static const struct vm_operations_struct xfs_file_vm_ops = {
        .fault          = xfs_filemap_fault,
        .huge_fault     = xfs_filemap_huge_fault,
        .map_pages      = filemap_map_pages,
        .page_mkwrite   = xfs_filemap_page_mkwrite,
        .pfn_mkwrite    = xfs_filemap_pfn_mkwrite,
};

STATIC int
xfs_file_mmap(
        struct file     *filp,
        struct vm_area_struct *vma)
{
        /*
         * We don't support synchronous mappings for non-DAX files. At least
         * until someone comes with a sensible use case.
         */
        if (!IS_DAX(file_inode(filp)) && (vma->vm_flags & VM_SYNC))
                return -EOPNOTSUPP;

        file_accessed(filp);
        vma->vm_ops = &xfs_file_vm_ops;
        if (IS_DAX(file_inode(filp)))
                vma->vm_flags |= VM_HUGEPAGE;
        return 0;
}

const struct file_operations xfs_file_operations = {
        .llseek         = xfs_file_llseek,
        .read_iter      = xfs_file_read_iter,
        .write_iter     = xfs_file_write_iter,
        .splice_read    = generic_file_splice_read,
        .splice_write   = iter_file_splice_write,
        .iopoll         = iomap_dio_iopoll,
        .unlocked_ioctl = xfs_file_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = xfs_file_compat_ioctl,
#endif
        .mmap           = xfs_file_mmap,
        .mmap_supported_flags = MAP_SYNC,
        .open           = xfs_file_open,
        .release        = xfs_file_release,
        .fsync          = xfs_file_fsync,
        .get_unmapped_area = thp_get_unmapped_area,
        .fallocate      = xfs_file_fallocate,
        .remap_file_range = xfs_file_remap_range,
};

const struct file_operations xfs_dir_file_operations = {
        .open           = xfs_dir_open,
        .read           = generic_read_dir,
        .iterate_shared = xfs_file_readdir,
        .llseek         = generic_file_llseek,
        .unlocked_ioctl = xfs_file_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = xfs_file_compat_ioctl,
#endif
        .fsync          = xfs_dir_fsync,
};