From: Theodore Ts'o <tytso@mit.edu>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-ext4@vger.kernel.org
Subject: Re: [PATCH 09/19] e2fsck: correctly preserve fs flags when modifying ignore-csum-error flag
Date: Sat, 2 Aug 2014 22:48:52 -0400 [thread overview]
Message-ID: <20140803024852.GI24826@thunk.org> (raw)
In-Reply-To: <20140801181241.12496.65228.stgit@birch.djwong.org>
On Fri, Aug 01, 2014 at 11:12:41AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> When we need to modify the "ignore checksum error" behavior flag to
> get us past a library call, it's possible that the library call can
> result in other flag bits being changed. Therefore, it is not correct
> to restore unconditionally the previous flags value, since this will
> have unintended side effects on the other fs->flags; nor is it correct
> to assume that we can unconditionally set (or clear) the "ignore csum
> error" flag bit. Therefore, we must merge the previous value of the
> "ignore csum error" flag with the value of flags after the call.
>
> Note that we want to leave checksum verification on as much as
> possible because doing so exposes e2fsck bugs where two metadata
> blocks are "sharing" the same disk block, and attempting to fix one
> before relocating the other causes major filesystem damage. The
> damage is much more obvious when a previously checked piece of
> metadata suddenly fails in a subsequent pass.
>
> The modifications to the pass 2, 3, and 3A code are justified as
> follows: When e2fsck encounters a block of directory entries and
> cannot find the placeholder entry at the end that contains the
> checksum, it will try to insert the placeholder. If that fails, it
> will schedule the directory for a pass 3A reconstruction. Until that
> happens, we don't want directory block writing (pass 2), block
> iteration (pass 3), or block reading (pass 3A) to fail due to checksum
> errors, because failing to find the placeholder is itself a checksum
> verification error, which causes e2fsck to abort without fixing
> anything.
>
> The e2fsck call to ext2fs_read_bitmaps must never fail due to a
> checksum error because e2fsck subsequently (a) verifies the bitmaps
> itself; or (b) decides that they don't match what has been observed,
> and rewrites them.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Applied, thanks.
- Ted
next prev parent reply other threads:[~2014-08-03 2:48 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-01 18:11 [PATCH 00/19] e2fsprogs patchbomb 7/14, part 2.1 Darrick J. Wong
2014-08-01 18:11 ` [PATCH 01/19] e2fuzz: fix fs handle cleanup when closing fails Darrick J. Wong
2014-08-03 2:22 ` Theodore Ts'o
2014-08-01 18:11 ` [PATCH 02/19] e2fsck: never free critical metadata blocks in the block found map Darrick J. Wong
2014-08-03 2:22 ` Theodore Ts'o
2014-08-01 18:11 ` [PATCH 03/19] e2fsck: use root dir for lost+found when really desperate Darrick J. Wong
2014-08-03 2:25 ` Theodore Ts'o
2014-08-05 0:58 ` Darrick J. Wong
2014-08-05 2:06 ` Theodore Ts'o
2014-08-01 18:12 ` [PATCH 04/19] dumpe2fs: complain when checksum verification fails Darrick J. Wong
2014-08-03 2:26 ` Theodore Ts'o
2014-08-01 18:12 ` [PATCH 05/19] libext2fs: check EA block headers when reading in the block Darrick J. Wong
2014-08-03 2:33 ` Theodore Ts'o
2014-08-01 18:12 ` [PATCH 06/19] e2fsck: try to salvage extent blocks with bad checksums Darrick J. Wong
2014-08-03 2:33 ` Theodore Ts'o
2014-08-01 18:12 ` [PATCH 07/19] e2fsck: try to salvage corrupt directory entry blocks Darrick J. Wong
2014-08-03 2:33 ` Theodore Ts'o
2014-08-01 18:12 ` [PATCH 08/19] e2fsck: offer to clear inode table blocks that are insane Darrick J. Wong
2014-08-03 2:46 ` Theodore Ts'o
2014-08-01 18:12 ` [PATCH 09/19] e2fsck: correctly preserve fs flags when modifying ignore-csum-error flag Darrick J. Wong
2014-08-03 2:48 ` Theodore Ts'o [this message]
2014-08-01 18:12 ` [PATCH 10/19] libext2fs: Don't cache inodes that fail checksum verification Darrick J. Wong
2014-08-03 2:50 ` Theodore Ts'o
2014-08-01 18:12 ` [PATCH 11/19] e2fsck: disable checksum verification in a few select places Darrick J. Wong
2014-08-03 2:51 ` Theodore Ts'o
2014-08-01 18:13 ` [PATCH 12/19] e2fsck: always ask to fix an inode that fails checksum verification Darrick J. Wong
2014-08-03 2:55 ` Theodore Ts'o
2014-08-01 18:13 ` [PATCH 13/19] tests: add regression tests for EA blocks with bad checksums Darrick J. Wong
2014-08-03 3:42 ` Theodore Ts'o
2014-08-01 18:13 ` [PATCH 14/19] tests: add tests for handling of corrupt extents Darrick J. Wong
2014-08-03 3:47 ` Theodore Ts'o
2014-08-01 18:13 ` [PATCH 15/19] tests: add tests for directory entry blocks with checksum errors Darrick J. Wong
2014-08-03 3:49 ` Theodore Ts'o
2014-08-01 18:13 ` [PATCH 16/19] tests: add regression tests for MMP blocks with bad checksums Darrick J. Wong
2014-08-03 3:49 ` Theodore Ts'o
2014-08-01 18:13 ` [PATCH 17/19] tests: add regression tests for superblocks " Darrick J. Wong
2014-08-03 3:50 ` Theodore Ts'o
2014-08-01 18:13 ` [PATCH 18/19] tests: add regression tests for group descriptors " Darrick J. Wong
2014-08-03 3:51 ` Theodore Ts'o
2014-08-01 18:13 ` [PATCH 19/19] tests: add regression tests for inodes " Darrick J. Wong
2014-08-03 3:52 ` Theodore Ts'o
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