From: Leah Rumancik <leah.rumancik@gmail.com>
To: stable@vger.kernel.org
Cc: linux-xfs@vger.kernel.org, amir73il@gmail.com,
chandan.babu@oracle.com, fred@cloudflare.com,
"Darrick J. Wong" <djwong@kernel.org>,
Gao Xiang <hsiangkao@linux.alibaba.com>,
Dave Chinner <dchinner@redhat.com>,
Leah Rumancik <leah.rumancik@gmail.com>
Subject: [PATCH 6.1 14/24] xfs: invalidate block device page cache during unmount
Date: Wed, 1 May 2024 11:41:02 -0700 [thread overview]
Message-ID: <20240501184112.3799035-14-leah.rumancik@gmail.com> (raw)
In-Reply-To: <20240501184112.3799035-1-leah.rumancik@gmail.com>
From: "Darrick J. Wong" <djwong@kernel.org>
[ Upstream commit 032e160305f6872e590c77f11896fb28365c6d6c ]
Every now and then I see fstests failures on aarch64 (64k pages) that
trigger on the following sequence:
mkfs.xfs $dev
mount $dev $mnt
touch $mnt/a
umount $mnt
xfs_db -c 'path /a' -c 'print' $dev
99% of the time this succeeds, but every now and then xfs_db cannot find
/a and fails. This turns out to be a race involving udev/blkid, the
page cache for the block device, and the xfs_db process.
udev is triggered whenever anyone closes a block device or unmounts it.
The default udev rules invoke blkid to read the fs super and create
symlinks to the bdev under /dev/disk. For this, it uses buffered reads
through the page cache.
xfs_db also uses buffered reads to examine metadata. There is no
coordination between xfs_db and udev, which means that they can run
concurrently. Note there is no coordination between the kernel and
blkid either.
On a system with 64k pages, the page cache can cache the superblock and
the root inode (and hence the root dir) with the same 64k page. If
udev spawns blkid after the mkfs and the system is busy enough that it
is still running when xfs_db starts up, they'll both read from the same
page in the pagecache.
The unmount writes updated inode metadata to disk directly. The XFS
buffer cache does not use the bdev pagecache, nor does it invalidate the
pagecache on umount. If the above scenario occurs, the pagecache no
longer reflects what's on disk, xfs_db reads the stale metadata, and
fails to find /a. Most of the time this succeeds because closing a bdev
invalidates the page cache, but when processes race, everyone loses.
Fix the problem by invalidating the bdev pagecache after flushing the
bdev, so that xfs_db will see up to date metadata.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/xfs_buf.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index dde346450952..54c774af6e1c 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1945,6 +1945,7 @@ xfs_free_buftarg(
list_lru_destroy(&btp->bt_lru);
blkdev_issue_flush(btp->bt_bdev);
+ invalidate_bdev(btp->bt_bdev);
fs_put_dax(btp->bt_daxdev, btp->bt_mount);
kmem_free(btp);
--
2.45.0.rc1.225.g2a3ae87e7f-goog
next prev parent reply other threads:[~2024-05-01 18:41 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-01 18:40 [PATCH 6.1 01/24] xfs: write page faults in iomap are not buffered writes Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 02/24] xfs: punching delalloc extents on write failure is racy Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 03/24] xfs: use byte ranges for write cleanup ranges Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 04/24] xfs,iomap: move delalloc punching to iomap Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 05/24] iomap: buffered write failure should not truncate the page cache Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 06/24] xfs: xfs_bmap_punch_delalloc_range() should take a byte range Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 07/24] iomap: write iomap validity checks Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 08/24] xfs: use iomap_valid method to detect stale cached iomaps Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 09/24] xfs: drop write error injection is unfixable, remove it Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 10/24] xfs: fix off-by-one-block in xfs_discard_folio() Leah Rumancik
2024-05-01 18:40 ` [PATCH 6.1 11/24] xfs: fix incorrect error-out in xfs_remove Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 12/24] xfs: fix sb write verify for lazysbcount Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 13/24] xfs: fix incorrect i_nlink caused by inode racing Leah Rumancik
2024-05-01 18:41 ` Leah Rumancik [this message]
2024-05-01 18:41 ` [PATCH 6.1 15/24] xfs: attach dquots to inode before reading data/cow fork mappings Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 16/24] xfs: wait iclog complete before tearing down AIL Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 17/24] xfs: fix super block buf log item UAF during force shutdown Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 18/24] xfs: hoist refcount record merge predicates Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 19/24] xfs: estimate post-merge refcounts correctly Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 20/24] xfs: invalidate xfs_bufs when allocating cow extents Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 21/24] xfs: allow inode inactivation during a ro mount log recovery Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 22/24] xfs: fix log recovery when unknown rocompat bits are set Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 23/24] xfs: get root inode correctly at bulkstat Leah Rumancik
2024-05-01 18:41 ` [PATCH 6.1 24/24] xfs: short circuit xfs_growfs_data_private() if delta is zero Leah Rumancik
2024-05-04 9:16 ` [PATCH 6.1 01/24] xfs: write page faults in iomap are not buffered writes Greg KH
2024-05-04 18:17 ` Amir Goldstein
2024-05-06 17:52 ` Leah Rumancik
2024-05-22 14:11 ` Greg KH
2024-05-22 21:55 ` Leah Rumancik
2024-05-23 7:08 ` Greg KH
2024-05-23 11:06 ` Greg KH
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