Commit 3b0fe478 authored by Dave Chinner's avatar Dave Chinner Committed by Dave Chinner
Browse files

xfs: Don't use reserved blocks for data blocks with DAX 



Commit 1ca19157 ("xfs: Don't use unwritten extents for DAX") enabled
the DAX allocation call to dip into the reserve pool in case it was
converting unwritten extents rather than allocating blocks. This was
a direct copy of the unwritten extent conversion code, but had an
unintended side effect of allowing normal data block allocation to
use the reserve pool. Hence normal block allocation could deplete
the reserve pool and prevent unwritten extent conversion at ENOSPC,
hence violating fallocate guarantees on preallocated space.

Fix it by checking whether the incoming map from __xfs_get_blocks()
spans an unwritten extent and only use the reserve pool if the
allocation covers an unwritten extent.

Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Tested-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent 16830985

fs/xfs/xfs_iomap.c

+8 −3
Original line number Original line Diff line number Diff line
@@ -203,15 +203,20 @@ xfs_iomap_write_direct( 
	 * this outside the transaction context, but if we commit and then crash

	 * this outside the transaction context, but if we commit and then crash

	 * we may not have zeroed the blocks and this will be exposed on

	 * we may not have zeroed the blocks and this will be exposed on

	 * recovery of the allocation. Hence we must zero before commit.

	 * recovery of the allocation. Hence we must zero before commit.

	 *

	 * Further, if we are mapping unwritten extents here, we need to zero

	 * Further, if we are mapping unwritten extents here, we need to zero

	 * and convert them to written so that we don't need an unwritten extent

	 * and convert them to written so that we don't need an unwritten extent

	 * callback for DAX. This also means that we need to be able to dip into

	 * callback for DAX. This also means that we need to be able to dip into

	 * the reserve block pool if there is no space left but we need to do

	 * the reserve block pool for bmbt block allocation if there is no space

	 * unwritten extent conversion.

	 * left but we need to do unwritten extent conversion.

	 */

	 */



	if (IS_DAX(VFS_I(ip))) {

	if (IS_DAX(VFS_I(ip))) {

		bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;

		bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;

		if (ISUNWRITTEN(imap)) {

			tp->t_flags |= XFS_TRANS_RESERVE;

			tp->t_flags |= XFS_TRANS_RESERVE;

			resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;

		}

	}

	}

	error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,

	error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,

				  resblks, resrtextents);

				  resblks, resrtextents);

CRA Git | Maintained and supported by SUSTech CRA and CCSE