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authorJan Kara <jack@suse.cz>2009-06-24 17:31:40 +0200
committerJan Kara <jack@suse.cz>2009-07-15 21:30:07 +0200
commit1e9fd53b783ea646de3ee09a4574afeb6778d504 (patch)
tree0b87e9ca83c612a1c3c5b91a359f8604cde48c45 /include
parent9eaaa2d5759837402ec5eee13b2a97921808c3eb (diff)
jbd: Fix a race between checkpointing code and journal_get_write_access()
The following race can happen: CPU1 CPU2 checkpointing code checks the buffer, adds it to an array for writeback do_get_write_access() ... lock_buffer() unlock_buffer() flush_batch() submits the buffer for IO __jbd_journal_file_buffer() So a buffer under writeout is returned from do_get_write_access(). Since the filesystem code relies on the fact that journaled buffers cannot be written out, it does not take the buffer lock and so it can modify buffer while it is under writeout. That can lead to a filesystem corruption if we crash at the right moment. The similar problem can happen with the journal_get_create_access() path. We fix the problem by clearing the buffer dirty bit under buffer_lock even if the buffer is on BJ_None list. Actually, we clear the dirty bit regardless the list the buffer is in and warn about the fact if the buffer is already journalled. Thanks for spotting the problem goes to dingdinghua <dingdinghua85@gmail.com>. Reported-by: dingdinghua <dingdinghua85@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
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