Commit ee70daab authored by Eryu Guan's avatar Eryu Guan Committed by Darrick J. Wong
Browse files

xfs: update i_size after unwritten conversion in dio completion 



Since commit d531d91d ("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: default avatarBrian Foster <bfoster@redhat.com>
Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
Signed-off-by: default avatarEryu Guan <eguan@redhat.com>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 546e7be8

fs/xfs/xfs_aops.c

+2 −1
Original line number Diff line number Diff line
@@ -343,7 +343,8 @@ xfs_end_io( 
		error = xfs_reflink_end_cow(ip, offset, size);

		break;

	case XFS_IO_UNWRITTEN:

		error = xfs_iomap_write_unwritten(ip, offset, size);

		/* writeback should never update isize */

		error = xfs_iomap_write_unwritten(ip, offset, size, false);

		break;

	default:

		ASSERT(!xfs_ioend_is_append(ioend) || ioend->io_append_trans);

fs/xfs/xfs_file.c

+19 −14
Original line number Diff line number Diff line
@@ -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)

		error = xfs_setfilesize(ip, offset, size);

	} else {

		spin_unlock(&ip->i_flags_lock);

	}



	return error;

}

fs/xfs/xfs_iomap.c

+5 −2
Original line number Diff line number Diff line
@@ -829,7 +829,8 @@ int 
xfs_iomap_write_unwritten(

	xfs_inode_t	*ip,

	xfs_off_t	offset,

	xfs_off_t	count)

	xfs_off_t	count,

	bool		update_isize)

{

	xfs_mount_t	*mp = ip->i_mount;

	xfs_fileoff_t	offset_fsb;
@@ -840,6 +841,7 @@ xfs_iomap_write_unwritten( 
	xfs_trans_t	*tp;

	xfs_bmbt_irec_t imap;

	struct xfs_defer_ops dfops;

	struct inode	*inode = VFS_I(ip);

	xfs_fsize_t	i_size;

	uint		resblks;

	int		error;
@@ -899,7 +901,8 @@ xfs_iomap_write_unwritten( 
		i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb);

		if (i_size > offset + count)

			i_size = offset + count;



		if (update_isize && i_size > i_size_read(inode))

			i_size_write(inode, i_size);

		i_size = xfs_new_eof(ip, i_size);

		if (i_size) {

			ip->i_d.di_size = i_size;

fs/xfs/xfs_iomap.h

+1 −1
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, size_t, 
			struct xfs_bmbt_irec *, int);

int xfs_iomap_write_allocate(struct xfs_inode *, int, xfs_off_t,

			struct xfs_bmbt_irec *);

int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t);

int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool);



void xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *,

		struct xfs_bmbt_irec *);

fs/xfs/xfs_pnfs.c

+1 −1
Original line number Diff line number Diff line
@@ -274,7 +274,7 @@ xfs_fs_commit_blocks( 
					(end - 1) >> PAGE_SHIFT);

		WARN_ON_ONCE(error);



		error = xfs_iomap_write_unwritten(ip, start, length);

		error = xfs_iomap_write_unwritten(ip, start, length, false);

		if (error)

			goto out_drop_iolock;

	}

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