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xfs: update i_size after unwritten conversion in dio completion

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Since commit d531d91d69 ("xfs: always use unwritten extents for
direct I/O writes"), we start allocating unwritten extents for all
direct writes to allow appending aio in XFS.

But for dio writes that could extend file size we update the in-core
inode size first, then convert the unwritten extents to real
allocations at dio completion time in xfs_dio_write_end_io(). Thus a
racing direct read could see the new i_size and find the unwritten
extents first and read zeros instead of actual data, if the direct
writer also takes a shared iolock.

Fix it by updating the in-core inode size after the unwritten extent
conversion. To do this, introduce a new boolean argument to
xfs_iomap_write_unwritten() to tell if we want to update in-core
i_size or not.

Suggested-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Eryu Guan
2017-09-21 11:26:18 -07:00
committed by Darrick J. Wong
parent 546e7be824
commit ee70daaba8
5 changed files with 28 additions and 19 deletions
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33
fs/xfs/xfs_file.c
View File

@ -434,7 +434,6 @@ xfs_dio_write_end_io(
struct inode *inode = file_inode(iocb->ki_filp);
struct xfs_inode *ip = XFS_I(inode);
loff_t offset = iocb->ki_pos;
bool update_size = false;
int error = 0;
trace_xfs_end_io_direct_write(ip, offset, size);
@ -445,6 +444,21 @@ xfs_dio_write_end_io(
if (size <= 0)
return 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
@ -459,20 +473,11 @@ xfs_dio_write_end_io(
spin_lock(&ip->i_flags_lock);
if (offset + size > i_size_read(inode)) {
i_size_write(inode, offset + size);
update_size = true;
}
spin_unlock(&ip->i_flags_lock);
if (flags & IOMAP_DIO_COW) {
error = xfs_reflink_end_cow(ip, offset, size);
if (error)
return error;
}
if (flags & IOMAP_DIO_UNWRITTEN)
error = xfs_iomap_write_unwritten(ip, offset, size);
else if (update_size)
spin_unlock(&ip->i_flags_lock);
error = xfs_setfilesize(ip, offset, size);
} else {
spin_unlock(&ip->i_flags_lock);
}
return error;
}