-kmem_cache_create: duplicate cache jbd_4k
-
-The jbd slab cache creation/deletion is racey. If multiple jbd based
-filesystems are mounted concurrently, and there are no other jbd based
-filesystems already mounted. Then we can race creating the slab caches
-since jbd_slab[] is not locked. This is not commonly observed because
-typically /root is mounted early with a jbd based filesystem making the
-race impossible. On our diskless systems /root does not use the jbd
-but we do have attached storage which does, and which is mounted in
-parallel. Basically our setup is similiar to what may be found in a
-NAS style appliance.
-
-This patch wraps all modifications to jbd_slab[] in the jbd_slab_lock
-to prevent this above race.
-
-LLNL Bug 291
-Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
-
-Index: linux+rh+chaos/fs/jbd/journal.c
-===================================================================
---- linux+rh+chaos.orig/fs/jbd/journal.c
-+++ linux+rh+chaos/fs/jbd/journal.c
-@@ -1979,6 +1979,7 @@ void * __jbd_kmalloc (const char *where,
- #define JBD_MAX_SLABS 5
- #define JBD_SLAB_INDEX(size) (size >> 11)
-
-+static DECLARE_RWSEM(jbd_slab_lock); /* protect jbd_slab[] */
- static kmem_cache_t *jbd_slab[JBD_MAX_SLABS];
- static const char *jbd_slab_names[JBD_MAX_SLABS] = {
- "jbd_1k", "jbd_2k", "jbd_4k", NULL, "jbd_8k"
-@@ -1988,24 +1989,27 @@ static void journal_destroy_jbd_slabs(vo
- {
- int i;
-
-+ down_write(&jbd_slab_lock);
- for (i = 0; i < JBD_MAX_SLABS; i++) {
- if (jbd_slab[i])
- kmem_cache_destroy(jbd_slab[i]);
- jbd_slab[i] = NULL;
- }
-+ up_write(&jbd_slab_lock);
- }
-
- static int journal_create_jbd_slab(size_t slab_size)
- {
-- int i = JBD_SLAB_INDEX(slab_size);
-+ int rc = 0, i = JBD_SLAB_INDEX(slab_size);
-
- BUG_ON(i >= JBD_MAX_SLABS);
-
- /*
- * Check if we already have a slab created for this size
- */
-+ down_write(&jbd_slab_lock);
- if (jbd_slab[i])
-- return 0;
-+ goto out_lock;
-
- /*
- * Create a slab and force alignment to be same as slabsize -
-@@ -2016,27 +2020,36 @@ static int journal_create_jbd_slab(size_
- slab_size, slab_size, 0, NULL, NULL);
- if (!jbd_slab[i]) {
- printk(KERN_EMERG "JBD: no memory for jbd_slab cache\n");
-- return -ENOMEM;
-+ rc = -ENOMEM;
- }
-- return 0;
-+out_lock:
-+ up_write(&jbd_slab_lock);
-+ return rc;
- }
-
- void * jbd_slab_alloc(size_t size, gfp_t flags)
- {
-+ void *ptr;
- int idx;
-
-+ down_read(&jbd_slab_lock);
- idx = JBD_SLAB_INDEX(size);
- BUG_ON(jbd_slab[idx] == NULL);
-- return kmem_cache_alloc(jbd_slab[idx], flags | __GFP_NOFAIL);
-+ ptr = kmem_cache_alloc(jbd_slab[idx], flags | __GFP_NOFAIL);
-+ up_read(&jbd_slab_lock);
-+
-+ return ptr;
- }
-
- void jbd_slab_free(void *ptr, size_t size)
- {
- int idx;
-
-+ down_read(&jbd_slab_lock);
- idx = JBD_SLAB_INDEX(size);
- BUG_ON(jbd_slab[idx] == NULL);
- kmem_cache_free(jbd_slab[idx], ptr);
-+ up_read(&jbd_slab_lock);
- }
-
- /*
-
git://git.whamcloud.com / fs / lustre-release.git / commitdiff