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Linux: Never sleep in kmem_cache_alloc(..., KM_NOSLEEP) (#14926) 

When a kmem cache is exhausted and needs to be expanded a new
slab is allocated.  KM_SLEEP callers can block and wait for the
allocation, but KM_NOSLEEP callers were incorrectly allowed to
block as well.

Resolve this by attempting an emergency allocation as a best
effort.  This may fail but that's fine since any KM_NOSLEEP
consumer is required to handle an allocation failure.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Adam Moss <c@yotes.com>
Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
This commit is contained in:
Brian Behlendorf 2023-06-07 10:43:43 -07:00 committed by Tony Hutter
parent 426d07d64c
commit 837e426c1f
1 changed files with 11 additions and 1 deletions
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12
module/os/linux/spl/spl-kmem-cache.c
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@ -1020,9 +1020,19 @@ spl_cache_grow(spl_kmem_cache_t *skc, int flags, void **obj)
ASSERT0(flags & ~KM_PUBLIC_MASK); ASSERT0(flags & ~KM_PUBLIC_MASK);
ASSERT(skc->skc_magic == SKC_MAGIC); ASSERT(skc->skc_magic == SKC_MAGIC);
ASSERT((skc->skc_flags & KMC_SLAB) == 0); ASSERT((skc->skc_flags & KMC_SLAB) == 0);
might_sleep();
*obj = NULL; *obj = NULL;
/*
* Since we can't sleep attempt an emergency allocation to satisfy
* the request. The only alterative is to fail the allocation but
* it's preferable try. The use of KM_NOSLEEP is expected to be rare.
*/
if (flags & KM_NOSLEEP)
return (spl_emergency_alloc(skc, flags, obj));
might_sleep();
/* /*
* Before allocating a new slab wait for any reaping to complete and * Before allocating a new slab wait for any reaping to complete and
* then return so the local magazine can be rechecked for new objects. * then return so the local magazine can be rechecked for new objects.