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authorDavidlohr Bueso <dave@stgolabs.net>2018-08-21 22:01:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-22 10:52:52 -0700
commit2d22ecf6db1c390974476758681ba4229018e774 (patch)
treea3e555c29ee83f0cff4bfded9355802bc9df0850
parent93f976b5190df32793908d49165f78e67fcb66cf (diff)
downloadlinux-2d22ecf6db1c390974476758681ba4229018e774.tar.bz2
lib/rhashtable: guarantee initial hashtable allocation
rhashtable_init() may fail due to -ENOMEM, thus making the entire api unusable. This patch removes this scenario, however unlikely. In order to guarantee memory allocation, this patch always ends up doing GFP_KERNEL|__GFP_NOFAIL for both the tbl as well as alloc_bucket_spinlocks(). Upon the first table allocation failure, we shrink the size to the smallest value that makes sense and retry with __GFP_NOFAIL semantics. With the defaults, this means that from 64 buckets, we retry with only 4. Any later issues regarding performance due to collisions or larger table resizing (when more memory becomes available) is the least of our problems. Link: http://lkml.kernel.org/r/20180712185241.4017-9-manfred@colorfullife.com Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--lib/rhashtable.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 238c8daa9852..310e29b51507 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -178,10 +178,11 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
size = nbuckets;
- if (tbl == NULL && gfp != GFP_KERNEL) {
+ if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) {
tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
nbuckets = 0;
}
+
if (tbl == NULL)
return NULL;
@@ -1057,9 +1058,16 @@ int rhashtable_init(struct rhashtable *ht,
}
}
+ /*
+ * This is api initialization and thus we need to guarantee the
+ * initial rhashtable allocation. Upon failure, retry with the
+ * smallest possible size with __GFP_NOFAIL semantics.
+ */
tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
- if (tbl == NULL)
- return -ENOMEM;
+ if (unlikely(tbl == NULL)) {
+ size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
+ tbl = bucket_table_alloc(ht, size, GFP_KERNEL | __GFP_NOFAIL);
+ }
atomic_set(&ht->nelems, 0);