Messages in this thread |  | | Date | Fri, 26 Jul 2019 18:55:08 -0400 | From | "Theodore Y. Ts'o" <> | Subject | Re: [PATCH] ext4: Fix deadlock on page reclaim |
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On Sat, Jul 27, 2019 at 08:44:23AM +1000, Dave Chinner wrote: > > > > This looks like something that could hit every file systems, so > > shouldn't we fix this in common code? We could also look into > > just using memalloc_nofs_save for the page cache allocation path > > instead of the per-mapping gfp_mask. > > I think it has to be the entire IO path - any allocation from the > underlying filesystem could recurse into the top level filesystem > and then deadlock if the memory reclaim submits IO or blocks on > IO completion from the upper filesystem. That's a bloody big hammer > for something that is only necessary when there are stacked > filesystems like this....
Yeah.... that's why using memalloc_nofs_save() probably makes the most sense, and dm_zoned should use that before it calls into ext4.
- Ted
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