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SubjectRe: hunt for 2.6.37 dm-crypt+ext4 corruption? (was: Re: dm-crypt barrier support is effective)
On Sun, Dec 12, 2010 at 07:11:28AM -0600, Jon Nelson wrote:
> I'm glad you've been able to reproduce the problem! If you should need
> any further assistance, please do not hesitate to ask.

This patch seems to fix the problem for me. (Unless the partition is
mounted with mblk_io_submit.)

Could you confirm that it fixes it for you as well?

Thanks!

- Ted

commit a8649d85bd0ab3be6014918bd9eae319a0ffc691
Author: Theodore Ts'o <tytso@mit.edu>
Date: Sun Dec 12 20:57:19 2010 -0500

ext4: Turn off multiple page-io submission by default

Jon Nelson has found a test case which causes postgresql to fail with
the error:

psql:t.sql:4: ERROR: invalid page header in block 38269 of relation base/16384/16581

Under memory pressure, it looks like part of a file can end up getting
replaced by zero's. Until we can figure out the cause, we'll roll
back the change and use block_write_full_page() instead of
ext4_bio_write_page(). The new, more efficient writing function can
be used via the mount option mblk_io_submit, so we can test and fix
the new page I/O code.

To reproduce the problem, install postgres 8.4 or 9.0, and pin enough
memory such that the system just at the end of triggering writeback
before running the following sql script:

begin;
create temporary table foo as select x as a, ARRAY[x] as b FROM
generate_series(1, 10000000 ) AS x;
create index foo_a_idx on foo (a);
create index foo_b_idx on foo USING GIN (b);
rollback;
If the temporary table is created on a hard drive partition which is
encrypted using dm_crypt, then under memory pressure, approximately
30-40% of the time, pgsql will issue the above failure.

This patch should fix this problem, and the problem will come back if
the file system is mounted with the mblk_io_submit mount option.

Reported-by: Jon Nelson <jnelson@jamponi.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 6a5edea..6eb598b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -910,6 +910,7 @@ struct ext4_inode_info {
#define EXT4_MOUNT_JOURNAL_CHECKSUM 0x800000 /* Journal checksums */
#define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT 0x1000000 /* Journal Async Commit */
#define EXT4_MOUNT_I_VERSION 0x2000000 /* i_version support */
+#define EXT4_MOUNT_MBLK_IO_SUBMIT 0x4000000
#define EXT4_MOUNT_DELALLOC 0x8000000 /* Delalloc support */
#define EXT4_MOUNT_DATA_ERR_ABORT 0x10000000 /* Abort on file data write */
#define EXT4_MOUNT_BLOCK_VALIDITY 0x20000000 /* Block validity checking */
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index bdbe699..e659597 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2125,9 +2125,12 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
*/
if (unlikely(journal_data && PageChecked(page)))
err = __ext4_journalled_writepage(page, len);
- else
+ else if (test_opt(inode->i_sb, MBLK_IO_SUBMIT))
err = ext4_bio_write_page(&io_submit, page,
len, mpd->wbc);
+ else
+ err = block_write_full_page(page,
+ noalloc_get_block_write, mpd->wbc);

if (!err)
mpd->pages_written++;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e32195d..fb15c9c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1026,6 +1026,8 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
!(def_mount_opts & EXT4_DEFM_NODELALLOC))
seq_puts(seq, ",nodelalloc");

+ if (test_opt(sb, MBLK_IO_SUBMIT))
+ seq_puts(seq, ",mblk_io_submit");
if (sbi->s_stripe)
seq_printf(seq, ",stripe=%lu", sbi->s_stripe);
/*
@@ -1239,8 +1241,8 @@ enum {
Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
Opt_noquota, Opt_ignore, Opt_barrier, Opt_nobarrier, Opt_err,
Opt_resize, Opt_usrquota, Opt_grpquota, Opt_i_version,
- Opt_stripe, Opt_delalloc, Opt_nodelalloc,
- Opt_block_validity, Opt_noblock_validity,
+ Opt_stripe, Opt_delalloc, Opt_nodelalloc, Opt_mblk_io_submit,
+ Opt_nomblk_io_submit, Opt_block_validity, Opt_noblock_validity,
Opt_inode_readahead_blks, Opt_journal_ioprio,
Opt_dioread_nolock, Opt_dioread_lock,
Opt_discard, Opt_nodiscard,
@@ -1304,6 +1306,8 @@ static const match_table_t tokens = {
{Opt_resize, "resize"},
{Opt_delalloc, "delalloc"},
{Opt_nodelalloc, "nodelalloc"},
+ {Opt_mblk_io_submit, "mblk_io_submit"},
+ {Opt_nomblk_io_submit, "nomblk_io_submit"},
{Opt_block_validity, "block_validity"},
{Opt_noblock_validity, "noblock_validity"},
{Opt_inode_readahead_blks, "inode_readahead_blks=%u"},
@@ -1725,6 +1729,12 @@ set_qf_format:
case Opt_nodelalloc:
clear_opt(sbi->s_mount_opt, DELALLOC);
break;
+ case Opt_mblk_io_submit:
+ set_opt(sbi->s_mount_opt, MBLK_IO_SUBMIT);
+ break;
+ case Opt_nomblk_io_submit:
+ clear_opt(sbi->s_mount_opt, MBLK_IO_SUBMIT);
+ break;
case Opt_stripe:
if (match_int(&args[0], &option))
return 0;

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