On Jun 4, 2015, at 2:39 AM, Jan Kara <jack@xxxxxxx> wrote: > > Hello, > > we were recently debugging an issue where customer was hitting > warnings in xfs_vm_releasepage() which was complaining that the > page it was called for has delay-allocated buffers. After some > debugging we realized that indeed try_to_release_page() call from > shrink_active_list() can happen for a page in arbitrary state (that > call happens only if buffer_heads_over_limit is set so that is > the reason why we normally don't see that). > > Hence comes my question: What are the rules for when releasepage() > can be called? And what is the expected outcome? We are certainly > guaranteed to hold page lock. try_to_release_page() also makes > sure the page isn't under writeback. But what is ->releasepage() > supposed to do with a dirty page? > Generally IFAIU we aren't supposed to discard dirty data but I > wouldn't bet on all filesystems getting it right because the > common call paths make sure page is clean. I would almost say we > should enforce !PageDirty in try_to_release_page() if it was not > for that ext3 nastyness of cleaning buffers under a dirty page - > hum, but maybe the right answer for that is ripping ext3 out of > tree (which would also allow us to get rid of some code in the > blocklayer for bouncing journaled data buffers when stable writes > are required). > > Thoughts? I've been an advocate of removing ext3 from the tree for a few years already. It doesn't do anything better than ext4, but it does a lot of things worse. Distros have been using CONFIG_EXT4_USE_FOR_EXT23 for several years now without problems AFAIK so this is safe even if users don't want to upgrade their on-disk features in case they want to be able to downgrade to an older kernel. Cheers, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
