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netfs: Fix missing alloc tagging of direct mempool allocations

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Commit 1d78d56c43 ("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: 1d78d56c43 ("netfs: Fix folio_queue ENOMEM in writeback by adding a mempool")
Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Closes: https://lore.kernel.org/all/0b004319-9ef7-437c-a4dd-174d6a9a83db@mailbox.org/
Tested-by: Erhard Furtner <erhard_f@mailbox.org>
Suggested-by: Suren Baghdasaryan <surenb@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Hao Ge <hao.ge@linux.dev>
Link: https://patch.msgid.link/20260923063759.34667-1-hao.ge@linux.dev
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Hao Ge 2026-09-23 14:37:59 +08:00 committed by Christian Brauner
parent 35d442ed1f
commit b78b728e21
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
3 changed files with 10 additions and 3 deletions
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4
fs/netfs/objects.c
View File

@ -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)

2
fs/netfs/rolling_buffer.c
View File

@ -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) {

7
include/linux/mempool.h
View File

@ -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,