On Sun 09-08-20 22:02:04, Mauricio Faria de Oliveira wrote:
> This checks during journal commit, right after calculating the
> checksum of a buffer head, whether its contents match the 'BUG'
> string (the cookie string in the test case userspace part.)
>
> If so, it sleeps 5 seconds for such contents to change (i.e.,
> so that the actual checksum changes from what was calculated.)
>
> And if it changed, set a flag to panic after committing to disk.
>
> Then, on filesystem remount/journal recovery there is an invalid
> checksum error, and recovery fails:
>
> $ sudo mount -o data=journal,journal_checksum $DEV $MNT
> [ 100.832223] EXT4-fs: Warning: mounting with data=journal disables
> delayed allocation, dioread_nolock, and O_DIRECT support!
> [ 100.837488] JBD2: Invalid checksum recovering data block 8706 in log
> [ 100.842010] JBD2: recovery failed
> [ 100.843045] EXT4-fs (loop0): error loading journal
> mount: /ext4: can't read superblock on /dev/loop0.
Nice to have this for testing but when you'll do some "official"
submission, just send this patch separately so that it's clear shouldn't be
included in the kernel...
Honza
> ---
> fs/jbd2/commit.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
> index 6d2da8ad0e6f..51f713089e35 100644
> --- a/fs/jbd2/commit.c
> +++ b/fs/jbd2/commit.c
> @@ -26,6 +26,11 @@
> #include <linux/bitops.h>
> #include <trace/events/jbd2.h>
>
> +#include <linux/printk.h>
> +#include <linux/delay.h>
> +
> +static journal_t *force_panic;
> +
> /*
> * IO end handler for temporary buffer_heads handling writes to the journal.
> */
> @@ -331,14 +336,35 @@ static void jbd2_block_tag_csum_set(journal_t *j, journal_block_tag_t *tag,
> __u32 csum32;
> __be32 seq;
>
> + // For the testcase
> + __u32 csum32_later;
> + __u8 *bh_data;
> +
> if (!jbd2_journal_has_csum_v2or3(j))
> return;
>
> seq = cpu_to_be32(sequence);
> addr = kmap_atomic(page);
> csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&seq, sizeof(seq));
> + csum32_later = csum32; // Copy csum32 to check again later
> csum32 = jbd2_chksum(j, csum32, addr + offset_in_page(bh->b_data),
> bh->b_size);
> +
> + // Check for testcase cookie 'BUG' in the buffer_head data.
> + bh_data = addr + offset_in_page(bh->b_data);
> + if (bh_data[0] == 'B' &&
> + bh_data[1] == 'U' &&
> + bh_data[2] == 'G') {
> + pr_info("TESTCASE: Cookie found. Waiting 5 seconds for changes.\n");
> + msleep(5000);
> + pr_info("TESTCASE: Cookie eaten. Resumed.\n");
> + }
> +
> + // Check the checksum again for changes/panic after commit.
> + csum32_later = jbd2_chksum(j, csum32_later, addr + offset_in_page(bh->b_data), bh->b_size);
> + if (csum32 != csum32_later)
> + force_panic = j;
> +
> kunmap_atomic(addr);
>
> if (jbd2_has_feature_csum3(j))
> @@ -885,6 +911,9 @@ void jbd2_journal_commit_transaction(journal_t *journal)
> blkdev_issue_flush(journal->j_dev, GFP_NOFS);
> }
>
> + if (force_panic == journal)
> + panic("TESTCASE: checksum changed; commit record done; panic!\n");
> +
> if (err)
> jbd2_journal_abort(journal, err);
>
> --
> 2.17.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
