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Date:   Fri, 29 Apr 2022 08:12:53 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Qu Wenruo <quwenruo.btrfs@gmx.com>
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Subject: Re: [PATCH RFC v2 04/12] btrfs: add btrfs_read_repair_ctrl to record
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On Fri, Apr 29, 2022 at 08:09:38AM +0800, Qu Wenruo wrote:
> On the other hand, we're already allocating memory inside endio
> function, for a long long time.
> 
> Check endio_readpage_release_extent(), they all need to pre-allocate
> memory for extent tree update (although using mostly ATOMIC gfp flags).
> 
> I guess it's an abuse and we would like to remove it in the long run?

Yes, we should handle it.  In practice small GFP_ATOMIC allocations do
not fail, so this probably hasn't been much of an issue.

Allocations that can be rather larger like the bitmaps on the other
hand do have a real chance of failing under enough memory pressure.