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author | Eric Sandeen <sandeen@redhat.com> | 2011-02-12 08:12:18 -0500 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2011-02-12 08:12:18 -0500 |
commit | 2892c15ddda6a76dc10b7499e56c0f3b892e5a69 (patch) | |
tree | bd2aa2add525d91991975e5678ef5bfe9175bdd8 /fs | |
parent | d50bdd5aa55127635fd8a5c74bd2abb256bd34e3 (diff) | |
download | lwn-2892c15ddda6a76dc10b7499e56c0f3b892e5a69.tar.gz lwn-2892c15ddda6a76dc10b7499e56c0f3b892e5a69.zip |
ext4: make grpinfo slab cache names static
In 2.6.37 I was running into oopses with repeated module
loads & unloads. I tracked this down to:
fb1813f4 ext4: use dedicated slab caches for group_info structures
(this was in addition to the features advert unload problem)
The kstrdup & subsequent kfree of the cache name was causing
a double free. In slub, at least, if I read it right it allocates
& frees the name itself, slab seems to do something different...
so in slub I think we were leaking -our- cachep->name, and double
freeing the one allocated by slub.
After getting lost in slab/slub/slob a bit, I just looked at other
sized-caches that get allocated. jbd2, biovec, sgpool all do it
more or less the way jbd2 does. Below patch follows the jbd2
method of dynamically allocating a cache at mount time from
a list of static names.
(This might also possibly fix a race creating the caches with
parallel mounts running).
[Folded in a fix from Dan Carpenter which fixed an off-by-one error in
the original patch]
Cc: stable@kernel.org
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/ext4/mballoc.c | 100 |
1 files changed, 60 insertions, 40 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 851f49b2f9d2..d1fe09aea73d 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -342,10 +342,15 @@ static struct kmem_cache *ext4_free_ext_cachep; /* We create slab caches for groupinfo data structures based on the * superblock block size. There will be one per mounted filesystem for * each unique s_blocksize_bits */ -#define NR_GRPINFO_CACHES \ - (EXT4_MAX_BLOCK_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE + 1) +#define NR_GRPINFO_CACHES 8 static struct kmem_cache *ext4_groupinfo_caches[NR_GRPINFO_CACHES]; +static const char *ext4_groupinfo_slab_names[NR_GRPINFO_CACHES] = { + "ext4_groupinfo_1k", "ext4_groupinfo_2k", "ext4_groupinfo_4k", + "ext4_groupinfo_8k", "ext4_groupinfo_16k", "ext4_groupinfo_32k", + "ext4_groupinfo_64k", "ext4_groupinfo_128k" +}; + static void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap, ext4_group_t group); static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap, @@ -2414,6 +2419,55 @@ err_freesgi: return -ENOMEM; } +static void ext4_groupinfo_destroy_slabs(void) +{ + int i; + + for (i = 0; i < NR_GRPINFO_CACHES; i++) { + if (ext4_groupinfo_caches[i]) + kmem_cache_destroy(ext4_groupinfo_caches[i]); + ext4_groupinfo_caches[i] = NULL; + } +} + +static int ext4_groupinfo_create_slab(size_t size) +{ + static DEFINE_MUTEX(ext4_grpinfo_slab_create_mutex); + int slab_size; + int blocksize_bits = order_base_2(size); + int cache_index = blocksize_bits - EXT4_MIN_BLOCK_LOG_SIZE; + struct kmem_cache *cachep; + + if (cache_index >= NR_GRPINFO_CACHES) + return -EINVAL; + + if (unlikely(cache_index < 0)) + cache_index = 0; + + mutex_lock(&ext4_grpinfo_slab_create_mutex); + if (ext4_groupinfo_caches[cache_index]) { + mutex_unlock(&ext4_grpinfo_slab_create_mutex); + return 0; /* Already created */ + } + + slab_size = offsetof(struct ext4_group_info, + bb_counters[blocksize_bits + 2]); + + cachep = kmem_cache_create(ext4_groupinfo_slab_names[cache_index], + slab_size, 0, SLAB_RECLAIM_ACCOUNT, + NULL); + + mutex_unlock(&ext4_grpinfo_slab_create_mutex); + if (!cachep) { + printk(KERN_EMERG "EXT4: no memory for groupinfo slab cache\n"); + return -ENOMEM; + } + + ext4_groupinfo_caches[cache_index] = cachep; + + return 0; +} + int ext4_mb_init(struct super_block *sb, int needs_recovery) { struct ext4_sb_info *sbi = EXT4_SB(sb); @@ -2421,9 +2475,6 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery) unsigned offset; unsigned max; int ret; - int cache_index; - struct kmem_cache *cachep; - char *namep = NULL; i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_offsets); @@ -2440,30 +2491,9 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery) goto out; } - cache_index = sb->s_blocksize_bits - EXT4_MIN_BLOCK_LOG_SIZE; - cachep = ext4_groupinfo_caches[cache_index]; - if (!cachep) { - char name[32]; - int len = offsetof(struct ext4_group_info, - bb_counters[sb->s_blocksize_bits + 2]); - - sprintf(name, "ext4_groupinfo_%d", sb->s_blocksize_bits); - namep = kstrdup(name, GFP_KERNEL); - if (!namep) { - ret = -ENOMEM; - goto out; - } - - /* Need to free the kmem_cache_name() when we - * destroy the slab */ - cachep = kmem_cache_create(namep, len, 0, - SLAB_RECLAIM_ACCOUNT, NULL); - if (!cachep) { - ret = -ENOMEM; - goto out; - } - ext4_groupinfo_caches[cache_index] = cachep; - } + ret = ext4_groupinfo_create_slab(sb->s_blocksize); + if (ret < 0) + goto out; /* order 0 is regular bitmap */ sbi->s_mb_maxs[0] = sb->s_blocksize << 3; @@ -2520,7 +2550,6 @@ out: if (ret) { kfree(sbi->s_mb_offsets); kfree(sbi->s_mb_maxs); - kfree(namep); } return ret; } @@ -2734,7 +2763,6 @@ int __init ext4_init_mballoc(void) void ext4_exit_mballoc(void) { - int i; /* * Wait for completion of call_rcu()'s on ext4_pspace_cachep * before destroying the slab cache. @@ -2743,15 +2771,7 @@ void ext4_exit_mballoc(void) kmem_cache_destroy(ext4_pspace_cachep); kmem_cache_destroy(ext4_ac_cachep); kmem_cache_destroy(ext4_free_ext_cachep); - - for (i = 0; i < NR_GRPINFO_CACHES; i++) { - struct kmem_cache *cachep = ext4_groupinfo_caches[i]; - if (cachep) { - char *name = (char *)kmem_cache_name(cachep); - kmem_cache_destroy(cachep); - kfree(name); - } - } + ext4_groupinfo_destroy_slabs(); ext4_remove_debugfs_entry(); } |