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From: "Darrick J. Wong" <djwong@kernel.org>
To: sandeen@sandeen.net, djwong@kernel.org
Cc: Dave Chinner <dchinner@redhat.com>, linux-xfs@vger.kernel.org
Subject: [PATCH 22/43] xfs: rework attr2 feature and mount options
Date: Mon, 13 Sep 2021 19:42:00 -0700	[thread overview]
Message-ID: <163158732017.1604118.6704125945588625133.stgit@magnolia> (raw)
In-Reply-To: <163158719952.1604118.14415288328687941574.stgit@magnolia>

From: Dave Chinner <dchinner@redhat.com>

Source kernel commit: e23b55d537c9be60ae918fa6c3be0d699986f346

The attr2 feature is somewhat unique in that it has both a superblock
feature bit to enable it and mount options to enable and disable it.

Back when it was first introduced in 2005, attr2 was disabled unless
either the attr2 superblock feature bit was set, or the attr2 mount
option was set. If the superblock feature bit was not set but the
mount option was set, then when the first attr2 format inode fork
was created, it would set the superblock feature bit. This is as it
should be - the superblock feature bit indicated the presence of the
attr2 on disk format.

The noattr2 mount option, however, did not affect the superblock
feature bit. If noattr2 was specified, the on-disk superblock
feature bit was ignored and the code always just created attr1
format inode forks.  If neither of the attr2 or noattr2 mounts
option were specified, then the behaviour was determined by the
superblock feature bit.

This was all pretty sane.

Fast foward 3 years, and we are dealing with fallout from the
botched sb_features2 addition and having to deal with feature
mismatches between the sb_features2 and sb_bad_features2 fields. The
attr2 feature bit was one of these flags. The reconciliation was
done well after mount option parsing and, unfortunately, the feature
reconciliation had a bug where it ignored the noattr2 mount option.

For reasons lost to the mists of time, it was decided that resolving
this issue in commit 7c12f296500e ("[XFS] Fix up noattr2 so that it
will properly update the versionnum and features2 fields.") required
noattr2 to clear the superblock attr2 feature bit.  This greatly
complicated the attr2 behaviour and broke rules about feature bits
needing to be set when those specific features are present in the
filesystem.

By complicated, I mean that it introduced problems due to feature
bit interactions with log recovery. All of the superblock feature
bit checks are done prior to log recovery, but if we crash after
removing a feature bit, then on the next mount we see the feature
bit in the unrecovered superblock, only to have it go away after the
log has been replayed.  This means our mount time feature processing
could be all wrong.

Hence you can mount with noattr2, crash shortly afterwards, and
mount again without attr2 or noattr2 and still have attr2 enabled
because the second mount sees attr2 still enabled in the superblock
before recovery runs and removes the feature bit. It's just a mess.

Further, this is all legacy code as the v5 format requires attr2 to
be enabled at all times and it cannot be disabled.  i.e. the noattr2
mount option returns an error when used on v5 format filesystems.

To straighten this all out, this patch reverts the attr2/noattr2
mount option behaviour back to the original behaviour. There is no
reason for disabling attr2 these days, so we will only do this when
the noattr2 mount option is set. This will not remove the superblock
feature bit. The superblock bit will provide the default behaviour
and only track whether attr2 is present on disk or not. The attr2
mount option will enable the creation of attr2 format inode forks,
and if the superblock feature bit is not set it will be added when
the first attr2 inode fork is created.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 libxfs/xfs_format.h |    7 -------
 1 file changed, 7 deletions(-)


diff --git a/libxfs/xfs_format.h b/libxfs/xfs_format.h
index 5d8a1291..ac739e6a 100644
--- a/libxfs/xfs_format.h
+++ b/libxfs/xfs_format.h
@@ -398,13 +398,6 @@ static inline void xfs_sb_version_addattr2(struct xfs_sb *sbp)
 	sbp->sb_features2 |= XFS_SB_VERSION2_ATTR2BIT;
 }
 
-static inline void xfs_sb_version_removeattr2(struct xfs_sb *sbp)
-{
-	sbp->sb_features2 &= ~XFS_SB_VERSION2_ATTR2BIT;
-	if (!sbp->sb_features2)
-		sbp->sb_versionnum &= ~XFS_SB_VERSION_MOREBITSBIT;
-}
-
 static inline bool xfs_sb_version_hasprojid32bit(struct xfs_sb *sbp)
 {
 	return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) ||


  parent reply	other threads:[~2021-09-14  2:42 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-14  2:39 [PATCHSET 00/43] xfs: sync libxfs with 5.15 Darrick J. Wong
2021-09-14  2:40 ` [PATCH 01/43] xfs_{copy,db,logprint,repair}: pass xfs_mount pointers instead of xfs_sb pointers Darrick J. Wong
2021-09-14  2:40 ` [PATCH 02/43] xfs: remove support for disabling quota accounting on a mounted file system Darrick J. Wong
2021-09-14  2:40 ` [PATCH 03/43] xfs: remove the active vs running quota differentiation Darrick J. Wong
2021-09-14  2:40 ` [PATCH 04/43] xfs: replace kmem_alloc_large() with kvmalloc() Darrick J. Wong
2021-09-14  2:40 ` [PATCH 05/43] xfs: allow setting and clearing of log incompat feature flags Darrick J. Wong
2021-09-14  2:40 ` [PATCH 06/43] xfs: add attr state machine tracepoints Darrick J. Wong
2021-09-14  2:40 ` [PATCH 07/43] xfs: Rename __xfs_attr_rmtval_remove Darrick J. Wong
2021-09-14  2:40 ` [PATCH 08/43] xfs: make xfs_rtalloc_query_range input parameters const Darrick J. Wong
2021-09-14  2:40 ` [PATCH 09/43] xfs: make the key parameters to all btree key comparison functions const Darrick J. Wong
2021-09-14  2:40 ` [PATCH 10/43] xfs: make the key parameters to all btree query range " Darrick J. Wong
2021-09-14  2:41 ` [PATCH 11/43] xfs: make the record pointer passed to query_range " Darrick J. Wong
2021-09-14  2:41 ` [PATCH 12/43] xfs: mark the record passed into btree init_key functions as const Darrick J. Wong
2021-09-14  2:41 ` [PATCH 13/43] xfs: make the keys and records passed to btree inorder functions const Darrick J. Wong
2021-09-14  2:41 ` [PATCH 14/43] xfs: mark the record passed into xchk_btree functions as const Darrick J. Wong
2021-09-14  2:41 ` [PATCH 15/43] xfs: make the pointer passed to btree set_root functions const Darrick J. Wong
2021-09-14  2:41 ` [PATCH 16/43] xfs: make the start pointer passed to btree alloc_block " Darrick J. Wong
2021-09-14  2:41 ` [PATCH 17/43] xfs: make the start pointer passed to btree update_lastrec " Darrick J. Wong
2021-09-14  2:41 ` [PATCH 18/43] xfs: constify btree function parameters that are not modified Darrick J. Wong
2021-09-14  2:41 ` [PATCH 19/43] xfs: resolve fork names in trace output Darrick J. Wong
2021-09-14  2:41 ` [PATCH 20/43] xfs: sb verifier doesn't handle uncached sb buffer Darrick J. Wong
2021-09-14  2:41 ` [PATCH 21/43] xfs: rename xfs_has_attr() Darrick J. Wong
2021-09-14  2:42 ` Darrick J. Wong [this message]
2021-09-14  2:42 ` [PATCH 23/43] xfs: reflect sb features in xfs_mount Darrick J. Wong
2021-09-14  2:42 ` [PATCH 24/43] xfs: replace xfs_sb_version checks with feature flag checks Darrick J. Wong
2021-09-14  2:42 ` [PATCH 25/43] xfs: convert mount flags to features Darrick J. Wong
2021-09-14  2:42 ` [PATCH 26/43] xfs: convert remaining mount flags to state flags Darrick J. Wong
2021-09-14  2:42 ` [PATCH 27/43] xfs: replace XFS_FORCED_SHUTDOWN with xfs_is_shutdown Darrick J. Wong
2021-09-14  2:42 ` [PATCH 28/43] xfs: convert xfs_fs_geometry to use mount feature checks Darrick J. Wong
2021-09-14  2:42 ` [PATCH 29/43] xfs: open code sb verifier " Darrick J. Wong
2021-09-14  2:42 ` [PATCH 30/43] xfs: convert xfs_sb_version_has checks to use mount features Darrick J. Wong
2021-09-14  2:42 ` [PATCH 31/43] libxlog: replace xfs_sb_version checks with feature flag checks Darrick J. Wong
2021-09-14  2:42 ` [PATCH 32/43] libxfs: " Darrick J. Wong
2021-09-14  2:43 ` [PATCH 33/43] xfs_{copy,db,logprint,repair}: " Darrick J. Wong
2021-09-14  2:43 ` [PATCH 34/43] xfs: remove unused xfs_sb_version_has wrappers Darrick J. Wong
2021-09-14  2:43 ` [PATCH 35/43] xfs: introduce xfs_sb_is_v5 helper Darrick J. Wong
2021-09-14  2:43 ` [PATCH 36/43] xfs: kill xfs_sb_version_has_v3inode() Darrick J. Wong
2021-09-14  2:43 ` [PATCH 37/43] libxfs: use opstate flags and functions for libxfs mount options Darrick J. Wong
2021-09-14  2:43 ` [PATCH 38/43] libxfs: remove pointless *XFS_MOUNT* flags Darrick J. Wong
2021-09-14  2:43 ` [PATCH 39/43] libxfs: always initialize internal buffer map Darrick J. Wong
2021-09-14  2:43 ` [PATCH 40/43] libxfs: replace XFS_BUF_SET_ADDR with a function Darrick J. Wong
2021-09-14  2:43 ` [PATCH 41/43] xfs: introduce xfs_buf_daddr() Darrick J. Wong
2021-09-14  2:43 ` [PATCH 42/43] xfs: convert bp->b_bn references to xfs_buf_daddr() Darrick J. Wong
2021-09-14  2:43 ` [PATCH 43/43] libxfs: rename buffer cache index variable b_bn Darrick J. Wong

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