On Wed, Aug 02, 2017 at 11:38:36AM +0300, Alex Lyakas wrote: > Hello Dave, > > Thank you for your analysis. It sounds like this issue exists in > recent kernels as well. It's effectively a zero day bug. The two-transaction conversion to leaf form is recognisable in this commit from Jun 1995: http://oss.sgi.com/cgi-bin/gitweb.cgi?p=archive/xfs-import.git;a=commitdiff;h=d4e0d38051ce61f9d8f330f59e0a99ed710d5f9e This was about a month after attr support first shows up in the XFS commit history, so it's been there forever.... > We are reviewing some of the paths that operate xfs_buf's, but still > we don't have enough understanding on how to properly lock out the > xfs_buf from AIL grabbing it. Can you please point us at similar > flows, where such locking is done? It's simple - if the buffer is locked, the AIL can't grab it. The buffer needs to be held locked across transaction commit and then rejoined to the new transaction after it is rolled. THis is acheived by using xfs_trans_bhold() in the initial transaction context, and after commit it is rejoined to the new transaction context. See the inode chunk allocation code in xfs_dir_ialloc() for an example of how this works. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
