On Sun, Mar 07, 2021 at 12:26:02PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> A recent log refactoring patchset from Brian Foster relaxed fsfreeze
> behavior with regards to the buffer cache -- now freeze only waits for
> pending buffer IO to finish, and does not try to drain the buffer cache
> LRU. As a result, fsfreeze should no longer stall indefinitely while
> fsmap runs. Drop the sb_start_write calls around fsmap invocations.
>
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_fsmap.c | 14 +++++---------
> 1 file changed, 5 insertions(+), 9 deletions(-)
>
>
> diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> index 9ce5e7d5bf8f..34f2b971ce43 100644
> --- a/fs/xfs/xfs_fsmap.c
> +++ b/fs/xfs/xfs_fsmap.c
> @@ -904,14 +904,6 @@ xfs_getfsmap(
> info.fsmap_recs = fsmap_recs;
> info.head = head;
>
> - /*
> - * If fsmap runs concurrently with a scrub, the freeze can be delayed
> - * indefinitely as we walk the rmapbt and iterate over metadata
> - * buffers. Freeze quiesces the log (which waits for the buffer LRU to
> - * be emptied) and that won't happen while we're reading buffers.
> - */
> - sb_start_write(mp->m_super);
> -
> /* For each device we support... */
> for (i = 0; i < XFS_GETFSMAP_DEVS; i++) {
> /* Is this device within the range the user asked for? */
> @@ -934,6 +926,11 @@ xfs_getfsmap(
> if (handlers[i].dev > head->fmh_keys[0].fmr_device)
> memset(&dkeys[0], 0, sizeof(struct xfs_fsmap));
>
> + /*
> + * Grab an empty transaction so that we can use its recursive
> + * buffer locking abilities to detect cycles in the rmapbt
> + * without deadlocking.
> + */
> error = xfs_trans_alloc_empty(mp, &tp);
> if (error)
> break;
Took me a moment to work out that this is just adding a comment
because it wasn't mentioned in the commit log. Somewhat unrelated to
the bug fix but it's harmless so I don't see any need for you to
do any extra work to respin this patch to remove it.
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
