On Jun 16, 2021, at 4:56 AM, Jan Kara <jack@xxxxxxx> wrote:
>
> JBD2 layer support triggers which are called when journaling layer moves
> buffer to a certain state. We can use the frozen trigger, which gets
> called when buffer data is frozen and about to be written out to the
> journal, to compute block checksums for some buffer types (similarly as
> does ocfs2). This avoids unnecessary repeated recomputation of the
> checksum (at the cost of larger window where memory corruption won't be
> caught by checksumming) and is even necessary when there are
> unsynchronized updaters of the checksummed data.
>
> So add argument to ext4_journal_get_write_access() and
> ext4_journal_get_create_access() which describes buffer type so that
> triggers can be set accordingly. This patch is mostly only a change of
> prototype of the above mentioned functions and a few small helpers. Real
> checksumming will come later.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
Comment inline.
>
> diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
> index be799040a415..f601e24b6015 100644
> --- a/fs/ext4/ext4_jbd2.c
> +++ b/fs/ext4/ext4_jbd2.c
> @@ -229,11 +231,18 @@ int __ext4_journal_get_write_access(const char *where, unsigned int line,
>
> if (ext4_handle_valid(handle)) {
> err = jbd2_journal_get_write_access(handle, bh);
> - if (err)
> + if (err) {
> ext4_journal_abort_handle(where, line, __func__, bh,
> handle, err);
> + return err;
> + }
> }
> - return err;
> + if (trigger_type == EXT4_JTR_NONE || !ext4_has_metadata_csum(sb))
> + return 0;
> + WARN_ON_ONCE(trigger_type >= EXT4_JOURNAL_TRIGGER_COUNT);
I'm not sure WARN_ON_ONCE() is enough here. This would essentially result
in executing a random (or maybe NULL) function pointer later on. Either
trigger_type should be checked early and return an error, or this should
be a BUG_ON() so that the crash happens here instead of in jbd context.
> + jbd2_journal_set_triggers(bh,
> + &EXT4_SB(sb)->s_journal_triggers[trigger_type].tr_triggers);
> + return 0;
> }
>
> /*
> @@ -304,17 +313,27 @@ int __ext4_forget(const char *where, unsigned int line,
> int __ext4_journal_get_create_access(const char *where, unsigned int line,
> - handle_t *handle, struct buffer_head *bh)
> + handle_t *handle, struct super_block *sb,
> + struct buffer_head *bh,
> + enum ext4_journal_trigger_type trigger_type)
> {
> - int err = 0;
> + int err;
>
> - if (ext4_handle_valid(handle)) {
> - err = jbd2_journal_get_create_access(handle, bh);
> - if (err)
> - ext4_journal_abort_handle(where, line, __func__,
> - bh, handle, err);
> + if (!ext4_handle_valid(handle))
> + return 0;
> +
> + err = jbd2_journal_get_create_access(handle, bh);
> + if (err) {
> + ext4_journal_abort_handle(where, line, __func__, bh, handle,
> + err);
> + return err;
> }
> - return err;
> + if (trigger_type == EXT4_JTR_NONE || !ext4_has_metadata_csum(sb))
> + return 0;
> + WARN_ON_ONCE(trigger_type >= EXT4_JOURNAL_TRIGGER_COUNT);
Same.
> + jbd2_journal_set_triggers(bh,
> + &EXT4_SB(sb)->s_journal_triggers[trigger_type].tr_triggers);
> + return 0;
> }
Cheers, Andreas
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