On Thu, Apr 22, 2021 at 11:04:11AM +0200, Jan Kara wrote: > Yes, I understand that. What I was more asking about is: Does it really > matter we leave those buffer heads and journal heads unreclaimed. I > understand it could be triggering premature OOM in theory but is it a > problem in practice? Was there some observed practical case for which this > was added or was it just added due to the theoretical concern? I was doing some research, and found the mail thread which inspired bdev_try_to_free_page(): https://lore.kernel.org/linux-ext4/20081202200647.72cc5807.toshi.okajima@xxxxxxxxxxxxxx/ >From what I can tell Toshi Okajima did have a test workload which would trigger blkdev_releasepage(). He didn't specify it in the mail thread as near as I can tell, but he did use it to test the page. Thinking about it, it shouldn't be hard to trigger it via something like: find /mnt -print0 | xargs -0 touch in a memory contrained box with a large file system attached (a bookshelf NAS scenario). Under the right circumstances, I'm pretty sure a premature OOM could be demonstrated. - Ted
