[PATCH 5.10 CANDIDATE 0/2] Two more xfs backports for 5.10.y (from v5.11)

[PATCH 5.10 CANDIDATE 0/2] Two more xfs backports for 5.10.y (from v5.11)

[Amir Goldstein]

Darrick,

These two backports were selected by Chandan for 5.4.y, but are
currently missing from 5.10.y.

I've put them through the usual kdevops testing routine.

This is the second time that I have considered patch #2 for 5.10.y.
The last time around, I observed increased the probablity of a known
buffer corruption assertion when running xfs/076, so I suspected
a regression, and dropped it from the submission [1].

At the time, the alleged regression happened only in the kdevops setup
and neither I nor Brain were able to understand why that happens [2].
This time around, the kdevops setup did not observe that odd regression.

Thanks,
Amir.

[1] https://lore.kernel.org/linux-xfs/20220601104547.260949-1-amir73il@gmail.com/
[2] https://lore.kernel.org/linux-xfs/YpY6hUknor2S1iMd@bfoster/T/#mf1add66b8309a75a8984f28ea08718f22033bce7

Brian Foster (1):
  xfs: don't reuse busy extents on extent trim

Darrick J. Wong (1):
  xfs: shut down the filesystem if we screw up quota reservation

 fs/xfs/xfs_extent_busy.c | 14 --------------
 fs/xfs/xfs_trans_dquot.c | 13 ++++++++++---
 2 files changed, 10 insertions(+), 17 deletions(-)

-- 
2.34.1

[PATCH 5.10 CANDIDATE 1/2] xfs: shut down the filesystem if we screw up quota reservation

[Amir Goldstein]

From: "Darrick J. Wong" <djwong@kernel.org>

commit 2a4bdfa8558ca2904dc17b83497dc82aa7fc05e9 upstream.

If we ever screw up the quota reservations enough to trip the
assertions, something's wrong with the quota code.  Shut down the
filesystem when this happens, because this is corruption.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/xfs/xfs_trans_dquot.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_trans_dquot.c b/fs/xfs/xfs_trans_dquot.c
index 288ea38c43ad..5ca210e6626c 100644
--- a/fs/xfs/xfs_trans_dquot.c
+++ b/fs/xfs/xfs_trans_dquot.c
@@ -16,6 +16,7 @@
 #include "xfs_quota.h"
 #include "xfs_qm.h"
 #include "xfs_trace.h"
+#include "xfs_error.h"
 
 STATIC void	xfs_trans_alloc_dqinfo(xfs_trans_t *);
 
@@ -708,9 +709,11 @@ xfs_trans_dqresv(
 					    XFS_TRANS_DQ_RES_INOS,
 					    ninos);
 	}
-	ASSERT(dqp->q_blk.reserved >= dqp->q_blk.count);
-	ASSERT(dqp->q_rtb.reserved >= dqp->q_rtb.count);
-	ASSERT(dqp->q_ino.reserved >= dqp->q_ino.count);
+
+	if (XFS_IS_CORRUPT(mp, dqp->q_blk.reserved < dqp->q_blk.count) ||
+	    XFS_IS_CORRUPT(mp, dqp->q_rtb.reserved < dqp->q_rtb.count) ||
+	    XFS_IS_CORRUPT(mp, dqp->q_ino.reserved < dqp->q_ino.count))
+		goto error_corrupt;
 
 	xfs_dqunlock(dqp);
 	return 0;
@@ -720,6 +723,10 @@ xfs_trans_dqresv(
 	if (xfs_dquot_type(dqp) == XFS_DQTYPE_PROJ)
 		return -ENOSPC;
 	return -EDQUOT;
+error_corrupt:
+	xfs_dqunlock(dqp);
+	xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+	return -EFSCORRUPTED;
 }
 
 
-- 
2.34.1

[PATCH 5.10 CANDIDATE 2/2] xfs: don't reuse busy extents on extent trim

[Amir Goldstein]

From: Brian Foster <bfoster@redhat.com>

commit 06058bc40534530e617e5623775c53bb24f032cb upstream.

Freed extents are marked busy from the point the freeing transaction
commits until the associated CIL context is checkpointed to the log.
This prevents reuse and overwrite of recently freed blocks before
the changes are committed to disk, which can lead to corruption
after a crash. The exception to this rule is that metadata
allocation is allowed to reuse busy extents because metadata changes
are also logged.

As of commit 97d3ac75e5e0 ("xfs: exact busy extent tracking"), XFS
has allowed modification or complete invalidation of outstanding
busy extents for metadata allocations. This implementation assumes
that use of the associated extent is imminent, which is not always
the case. For example, the trimmed extent might not satisfy the
minimum length of the allocation request, or the allocation
algorithm might be involved in a search for the optimal result based
on locality.

generic/019 reproduces a corruption caused by this scenario. First,
a metadata block (usually a bmbt or symlink block) is freed from an
inode. A subsequent bmbt split on an unrelated inode attempts a near
mode allocation request that invalidates the busy block during the
search, but does not ultimately allocate it. Due to the busy state
invalidation, the block is no longer considered busy to subsequent
allocation. A direct I/O write request immediately allocates the
block and writes to it. Finally, the filesystem crashes while in a
state where the initial metadata block free had not committed to the
on-disk log. After recovery, the original metadata block is in its
original location as expected, but has been corrupted by the
aforementioned dio.

This demonstrates that it is fundamentally unsafe to modify busy
extent state for extents that are not guaranteed to be allocated.
This applies to pretty much all of the code paths that currently
trim busy extents for one reason or another. Therefore to address
this problem, drop the reuse mechanism from the busy extent trim
path. This code already knows how to return partial non-busy ranges
of the targeted free extent and higher level code tracks the busy
state of the allocation attempt. If a block allocation fails where
one or more candidate extents is busy, we force the log and retry
the allocation.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/xfs/xfs_extent_busy.c | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/fs/xfs/xfs_extent_busy.c b/fs/xfs/xfs_extent_busy.c
index 5c2695a42de1..a4075685d9eb 100644
--- a/fs/xfs/xfs_extent_busy.c
+++ b/fs/xfs/xfs_extent_busy.c
@@ -344,7 +344,6 @@ xfs_extent_busy_trim(
 	ASSERT(*len > 0);
 
 	spin_lock(&args->pag->pagb_lock);
-restart:
 	fbno = *bno;
 	flen = *len;
 	rbp = args->pag->pagb_tree.rb_node;
@@ -363,19 +362,6 @@ xfs_extent_busy_trim(
 			continue;
 		}
 
-		/*
-		 * If this is a metadata allocation, try to reuse the busy
-		 * extent instead of trimming the allocation.
-		 */
-		if (!(args->datatype & XFS_ALLOC_USERDATA) &&
-		    !(busyp->flags & XFS_EXTENT_BUSY_DISCARDED)) {
-			if (!xfs_extent_busy_update_extent(args->mp, args->pag,
-							  busyp, fbno, flen,
-							  false))
-				goto restart;
-			continue;
-		}
-
 		if (bbno <= fbno) {
 			/* start overlap */
 
-- 
2.34.1

Re: [PATCH 5.10 CANDIDATE 0/2] Two more xfs backports for 5.10.y (from v5.11)

[Darrick J. Wong]

On Sun, Mar 26, 2023 at 08:06:21PM +0300, Amir Goldstein wrote:
> Darrick,
> 
> These two backports were selected by Chandan for 5.4.y, but are
> currently missing from 5.10.y.
> 
> I've put them through the usual kdevops testing routine.
> 
> This is the second time that I have considered patch #2 for 5.10.y.
> The last time around, I observed increased the probablity of a known
> buffer corruption assertion when running xfs/076, so I suspected
> a regression, and dropped it from the submission [1].
> 
> At the time, the alleged regression happened only in the kdevops setup
> and neither I nor Brain were able to understand why that happens [2].
> This time around, the kdevops setup did not observe that odd regression.

Heh, I had a roommate once whose name got misspelled to Brain on the
water bills, and I still chuckle every time I see that. ;)

Acked-by: Darrick J. Wong <djwong@kernel.org>

--D

> 
> Thanks,
> Amir.
> 
> [1] https://lore.kernel.org/linux-xfs/20220601104547.260949-1-amir73il@gmail.com/
> [2] https://lore.kernel.org/linux-xfs/YpY6hUknor2S1iMd@bfoster/T/#mf1add66b8309a75a8984f28ea08718f22033bce7
> 
> Brian Foster (1):
>   xfs: don't reuse busy extents on extent trim
> 
> Darrick J. Wong (1):
>   xfs: shut down the filesystem if we screw up quota reservation
> 
>  fs/xfs/xfs_extent_busy.c | 14 --------------
>  fs/xfs/xfs_trans_dquot.c | 13 ++++++++++---
>  2 files changed, 10 insertions(+), 17 deletions(-)
> 
> -- 
> 2.34.1
>