From: Dave Chinner <david@fromorbit.com>
To: linux-mm@kvack.org, linux-xfs@vger.kernel.org
Cc: akpm@linux-foundation.org, hch@lst.de, osalvador@suse.de,
elver@google.com, vbabka@suse.cz, andreyknvl@gmail.com
Subject: [PATCH 0/3] mm: fix nested allocation context filtering
Date: Tue, 30 Apr 2024 15:28:22 +1000 [thread overview]
Message-ID: <20240430054604.4169568-1-david@fromorbit.com> (raw)
This patchset is the followup to the comment I made earlier today:
https://lore.kernel.org/linux-xfs/ZjAyIWUzDipofHFJ@dread.disaster.area/
Tl;dr: Memory allocations that are done inside the public memory
allocation API need to obey the reclaim recursion constraints placed
on the allocation by the original caller, including the "don't track
recursion for this allocation" case defined by __GFP_NOLOCKDEP.
These nested allocations are generally in debug code that is
tracking something about the allocation (kmemleak, KASAN, etc) and
so are allocating private kernel objects that only that debug system
will use.
Neither the page-owner code nor the stack depot code get this right.
They also also clear GFP_ZONEMASK as a separate operation, which is
completely redundant because the constraint filter applied
immediately after guarantees that GFP_ZONEMASK bits are cleared.
kmemleak gets this filtering right. It preserves the allocation
constraints for deadlock prevention and clears all other context
flags whilst also ensuring that the nested allocation will fail
quickly, silently and without depleting emergency kernel reserves if
there is no memory available.
This can be made much more robust, immune to whack-a-mole games and
the code greatly simplified by lifting gfp_kmemleak_mask() to
include/linux/gfp.h and using that everywhere. Also document it so
that there is no excuse for not knowing about it when writing new
debug code that nests allocations.
Tested with lockdep, KASAN + page_owner=on and kmemleak=on over
multiple fstests runs with XFS.
next reply other threads:[~2024-04-30 5:46 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 5:28 Dave Chinner [this message]
2024-04-30 5:28 ` [PATCH 1/3] mm: lift gfp_kmemleak_mask() to gfp.h Dave Chinner
2024-04-30 12:39 ` Marco Elver
2024-04-30 5:28 ` [PATCH 2/3] stackdepot: use gfp_nested_mask() instead of open coded masking Dave Chinner
2024-04-30 12:39 ` Marco Elver
2024-04-30 5:28 ` [PATCH 3/3] mm/page-owner: " Dave Chinner
2024-04-30 9:35 ` [PATCH 0/3] mm: fix nested allocation context filtering Christoph Hellwig
2024-04-30 10:06 ` Vlastimil Babka
2024-05-01 8:06 ` Oscar Salvador
2024-05-02 17:05 ` Andrew Morton
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