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b=i62KZs0VBwe+7WBncDD2NIaGeytnxoCGW4Vafmq0m9+p38DyxbtEY9F5+z7w8RKUI at2jPMAUdLGsOUedUT/Qs/GhkYLvX5xwWmLR4E093NhOY2B5AsPmLMTIYd0n1b3eLE jhIHPNz/x+Rp64R6tyhnplcsec22FnQ4SrGhtQLsrwH0+Cm/NeU3z9pg0VBt9ToLhj Q7Zrc9xaStAscYiuWDpsqw2oUJ1Li0YUXbw7+rGS3g7rIksABijDxpbfG4K9ZwVYCC Z7i6jmG/FLBm6CXdF95+gRQYlDQL6tw6t5Wz5xcqudIbdlZZ1BYUfP78+H/98o7l4l QLY5FdGww5brQ== Message-ID: <0d798541-6486-44ff-ae57-f631d1465688@kernel.org> Date: Thu, 24 Sep 2026 11:36:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] netfs: Fix missing alloc tagging of direct mempool allocations Content-Language: en-US To: Hao Ge , David Howells , Paulo Alcantara , Harry Yoo , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , "Christian Brauner (Amutable)" , Suren Baghdasaryan , Christoph Hellwig Cc: netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Erhard Furtner , stable@vger.kernel.org References: <20260923063759.34667-1-hao.ge@linux.dev> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C4C3F140005 X-Stat-Signature: sag4f4tabsfdd34ae1crg8xrwn8b4g9u X-HE-Tag: 1790242585-436302 X-HE-Meta: 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 ThCMuGcT ph21okW+2wWbB/bAGXnlwwMBw9PDWvcKtpLJIacRI+bsYRJzjKLrsw890+CZtLia3dbVbt2bGJd1VKFhw2EVq3CKdJHYYIBNtDeREbHRZ0aELuellnwVqKtnGwo1alqemAXfJIS23csjFoPLoNmyq3qSV1QlE0XGbzi/I2J2X06443m0mEF9gP0HYD1V5f+epy2hs0aqBo63qR+tVo7NHe1O6a61kEYKeQfpuXvP+Et5NugH1fz6d+y+1M508OD3m52pm4aScc6pkUtKUIMDyfaYqtWblH9ykAfxhjsI9pMglQ7v5jdMLvBW5PQ4zNlLqhHUgthe/XdNFaGUeOdOTsuLu0FhzJDZMuAEOi7j5Fgb9AEUBubTPvV+iEQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: +Cc Christoph On 9/23/26 08:37, Hao Ge wrote: > Commit 1d78d56c43ef ("netfs: Fix folio_queue ENOMEM in writeback by > adding a mempool") added a mempool for the folio_queues and made the > request, subrequest and folio_queue allocations distinguish between > writeback and everything else. Writeback is part of memory reclaim > and must not fail due to ENOMEM, so it allocates under GFP_NOFS > through mempool_alloc(), which may dip into the pool's reserve and, > if that runs empty, wait for elements to be returned. The > GFP_KERNEL paths, which can return -ENOMEM to their callers, invoke > the pool's ->alloc() callback directly instead. > > The direct call, however, skips the alloc_hooks() wrapper that the > mempool_alloc() macro provides. The pool callbacks, mempool_alloc_slab() > and mempool_kmalloc(), call kmem_cache_alloc_noprof() and kmalloc_noprof() > and rely on current->alloc_tag having been set by the caller. With > CONFIG_MEM_ALLOC_PROFILING_DEBUG=y this leads to > > current->alloc_tag not set > WARNING: ./include/linux/alloc_tag.h:161 at __alloc_tagging_slab_alloc_hook > alloc_tag was not set > WARNING: ./include/linux/alloc_tag.h:166 at __alloc_tagging_slab_free_hook > > at allocation and free time respectively, as reported when reading > files on a CIFS mount. The allocations are also missing from > /proc/allocinfo. > > Wrap the direct ->alloc() invocations in alloc_hooks() with a new > mempool_alloc_noreserve() helper in include/linux/mempool.h, next to > the other alloc_hooks()-wrapped macros such as mempool_alloc(). The > GFP_KERNEL paths keep their failable allocation semantics, they just > get tagged now. > > Fixes: 1d78d56c43ef ("netfs: Fix folio_queue ENOMEM in writeback by adding a mempool") > Reported-by: Erhard Furtner > Closes: https://lore.kernel.org/all/0b004319-9ef7-437c-a4dd-174d6a9a83db@mailbox.org/ > Tested-by: Erhard Furtner > Suggested-by: Suren Baghdasaryan > Cc: stable@vger.kernel.org > Signed-off-by: Hao Ge Acked-by: Vlastimil Babka (SUSE) Seems ok enough as a hotfix. The naming perhaps isn't ideal, we have mempool_alloc_preallocated() already for the opposite case. Maybe mempool_alloc_no_preallocated() to complement it? Rather long though. I guess long-term it would be neater to have a mempool_alloc() variant with extra parameter that says if preallocated pool is allowed or not. The "gfp == GFP_KERNEL" check is probably not an universal one. mempool_alloc() is actually rather aggressive in getting objects from the pool before even attempting reclaim. Makes sense for I/O usecases but maybe not for this one? > --- > Changes in v2: > - Move the alloc_hooks() wrapper from fs/netfs/internal.h into > include/linux/mempool.h as mempool_alloc_noreserve(), per Suren's > suggestion, so it is not netfs-specific. > > v1 Link: https://lore.kernel.org/all/20260922023541.51532-1-hao.ge@linux.dev/ > --- > fs/netfs/objects.c | 4 ++-- > fs/netfs/rolling_buffer.c | 2 +- > include/linux/mempool.h | 7 +++++++ > 3 files changed, 10 insertions(+), 3 deletions(-) > > diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c > index 7f6a3e912602..ad549daa9c79 100644 > --- a/fs/netfs/objects.c > +++ b/fs/netfs/objects.c > @@ -34,7 +34,7 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping, > > rreq = mempool_alloc(mempool, gfp); > } else { > - rreq = mempool->alloc(gfp, mempool->pool_data); > + rreq = mempool_alloc_noreserve(mempool, gfp); > if (!rreq) > return ERR_PTR(-ENOMEM); > } > @@ -214,7 +214,7 @@ struct netfs_io_subrequest *netfs_alloc_subrequest(struct netfs_io_request *rreq > struct kmem_cache *cache = mempool->pool_data; > > if (rreq->gfp == GFP_KERNEL) > - subreq = mempool->alloc(rreq->gfp, mempool->pool_data); > + subreq = mempool_alloc_noreserve(mempool, rreq->gfp); > else > subreq = mempool_alloc(mempool, rreq->gfp); > if (!subreq) > diff --git a/fs/netfs/rolling_buffer.c b/fs/netfs/rolling_buffer.c > index 424e77a9a109..d30d5ef6d86e 100644 > --- a/fs/netfs/rolling_buffer.c > +++ b/fs/netfs/rolling_buffer.c > @@ -29,7 +29,7 @@ struct folio_queue *netfs_folioq_alloc(unsigned int rreq_id, gfp_t gfp, > struct folio_queue *fq; > > if (gfp == GFP_KERNEL) > - fq = netfs_folioq_pool.alloc(gfp, netfs_folioq_pool.pool_data); > + fq = mempool_alloc_noreserve(&netfs_folioq_pool, gfp); > else > fq = mempool_alloc(&netfs_folioq_pool, gfp); > if (fq) { > diff --git a/include/linux/mempool.h b/include/linux/mempool.h > index a0fa6d43e0dc..6da502aef2f7 100644 > --- a/include/linux/mempool.h > +++ b/include/linux/mempool.h > @@ -70,6 +70,13 @@ int mempool_alloc_bulk_noprof(struct mempool *pool, void **elem, > #define mempool_alloc_bulk(...) \ > alloc_hooks(mempool_alloc_bulk_noprof(__VA_ARGS__)) > > +/* > + * Allocate a new element without dipping into the pool's reserves or > + * waiting. Returns NULL on failure. > + */ > +#define mempool_alloc_noreserve(_pool, _gfp) \ > + alloc_hooks((_pool)->alloc(_gfp, (_pool)->pool_data)) > + > void *mempool_alloc_preallocated(struct mempool *pool) __malloc; > void mempool_free(void *element, struct mempool *pool); > unsigned int mempool_free_bulk(struct mempool *pool, void **elem,