Re: [PATCH 1/4] ext4: Support for checksumming from journal triggers
From: Andreas Dilger <hidden>
Date: 2021-06-16 19:56:34
On Jun 16, 2021, at 4:56 AM, Jan Kara [off-list ref] 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@suse.cz> ---
Comment inline.
quoted hunk ↗ jump to hunk
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.
quoted hunk ↗ jump to hunk
+ 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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