Re: mmotm 2008-12-09-15-24: memory corruption (bio slab)
From: Jens Axboe
Date: Wed Dec 10 2008 - 09:31:17 EST
On Wed, Dec 10 2008, Jens Axboe wrote:
> On Wed, Dec 10 2008, Jiri Slaby wrote:
> > Hi,
> >
> > on every bootup of this kernel, I get this (not sure if it is right after the moment when / gets mounted from md1):
> >
> > wlan0 renamed to wlan1
> > udev: renamed network interface wlan0 to wlan1
> > swap_cgroup: uses 7848 bytes of vmalloc for pointer array space and 4018176 bytes to hold mem_cgroup pointers on swap
> > swap_cgroup can be disabled by noswapaccount boot option.
> > Adding 2008084k swap on /dev/sdb6. Priority:-1 extents:1 across:2008084k
> > EXT3 FS on md1, internal journal
> > bio: create slab <bio-1> at 1
> > =============================================================================
> > BUG bio-1: Redzone overwritten
> > -----------------------------------------------------------------------------
> >
> > INFO: 0xffff88007bacf068-0xffff88007bacf06f. First byte 0x68 instead of 0xcc
> > INFO: Allocated in 0x6b6b6b6b6b6b6b6b age=10706345584330245030 cpu=1802201963 pid=1802201963
> > INFO: Freed in 0x6b6b6b6b6b6b6b6b age=6527005130130424742 cpu=1802201963 pid=1802201963
> > INFO: Slab 0xffffe20001b0dd48 objects=21 used=4 fp=0xffff88007bacf300 flags=0x40000000000000c3
> > INFO: Object 0xffff88007bacf000 @offset=0 fp=0x0000000000001000
> >
> > Object 0xffff88007bacf000: fd 6f 57 04 00 00 00 00 00 00 00 00 00 00 00 00 375oW.............
> > Object 0xffff88007bacf010: 80 86 c2 7c 00 88 ff ff 19 00 00 00 00 00 00 00 ..302|..377377........
> > Object 0xffff88007bacf020: 00 00 00 00 00 00 00 00 01 00 00 00 01 00 00 00 ................
> > Object 0xffff88007bacf030: 00 00 00 00 00 10 00 00 00 10 00 00 04 00 00 00 ................
> > Object 0xffff88007bacf040: ff ff ff ff 00 00 00 00 68 f0 ac 7b 00 88 ff ff 377377377377....h360254{..377377
> > Object 0xffff88007bacf050: b0 ad 49 80 ff ff ff ff 58 99 b7 7a 00 88 ff ff 260255I.377377377377X.267z..377377
> > Object 0xffff88007bacf060: 10 98 49 80 ff ff ff ff ..I.377377377377
> > Redzone 0xffff88007bacf068: 68 1b b1 01 00 e2 ff ff h.261..342377377
> > Padding 0xffff88007bacf0a8: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> > Padding 0xffff88007bacf0b8: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ
> > Pid: 815, comm: udevd Tainted: G W 2.6.28-rc7-mm1_64 #490
> > Call Trace:
> > <IRQ> [<ffffffff802b6ed6>] print_trailer+0x106/0x160
> > [<ffffffff802b7145>] check_bytes_and_report+0x125/0x180
> > [<ffffffff802b83d6>] check_object+0x66/0x280
> > [<ffffffff802b9e65>] __slab_free+0x225/0x370
> > [<ffffffff8028f5d2>] ? mempool_free_slab+0x12/0x20
> > [<ffffffff802bb7f2>] kmem_cache_free+0x72/0xa0
> > [<ffffffff8028f5d2>] mempool_free_slab+0x12/0x20
> > [<ffffffff8028f66a>] mempool_free+0x8a/0xa0
> > [<ffffffff802ea03d>] bio_free+0x4d/0x60
> > [<ffffffff8049981d>] dm_bio_destructor+0xd/0x10
> > [<ffffffff802e848b>] bio_put+0x2b/0x40
> > [<ffffffff8049ae39>] clone_endio+0x89/0xd0
> > [<ffffffff802e851c>] bio_endio+0x1c/0x40
> > [<ffffffff8034f42b>] req_bio_endio+0x8b/0xe0
> > [<ffffffff8034f527>] __end_that_request_first+0xa7/0x2b0
> > [<ffffffff8034f75c>] end_that_request_data+0x2c/0x70
> > [<ffffffff8034f80d>] blk_end_io+0x2d/0xb0
> > [<ffffffff8034f8be>] blk_end_request+0xe/0x10
> > [<ffffffff80418edb>] scsi_io_completion+0x13b/0x490
> > [<ffffffff8041250c>] scsi_finish_command+0xac/0xe0
> > [<ffffffff80418d1a>] scsi_softirq_done+0xba/0x140
> > [<ffffffff8043df0c>] ? ahci_interrupt+0x9c/0x5c0
> > [<ffffffff80353a85>] blk_done_softirq+0x75/0x90
> > [<ffffffff8025ab83>] ? sched_clock_cpu+0x143/0x190
> > [<ffffffff80244052>] __do_softirq+0xc2/0x190
> > [<ffffffff8020d6bc>] call_softirq+0x1c/0x30
> > [<ffffffff8020ea15>] do_softirq+0x45/0x90
> > [<ffffffff80243d9d>] irq_exit+0x8d/0xa0
> > [<ffffffff8020ecc5>] do_IRQ+0xc5/0x110
> > [<ffffffff8020cf93>] ret_from_intr+0x0/0xa
> > <EOI> <3>FIX bio-1: Restoring 0xffff88007bacf068-0xffff88007bacf06f=0xcc
> >
> > =============================================================================
> > BUG bio-1: Redzone overwritten
> > -----------------------------------------------------------------------------
> >
> > ffffffff8049981d is in dm_bio_destructor from drivers/md/dm.c.
> >
> > Inlined vecs doesn't fit to the allocated slab portion in my eyes, doesn't
> > the patch below make sense?
>
> Ah good, this looks like it's narrowing things down.
>
> > Enlarge bio slabs to include inlined vecs
> >
> > ---
> > fs/bio.c | 3 ++-
> > 1 files changed, 2 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/bio.c b/fs/bio.c
> > index 40b6488..cd1a439 100644
> > --- a/fs/bio.c
> > +++ b/fs/bio.c
> > @@ -68,7 +68,8 @@ static unsigned int bio_slab_nr, bio_slab_max;
> >
> > static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
> > {
> > - unsigned int sz = sizeof(struct bio) + extra_size;
> > + unsigned int sz = sizeof(struct bio) +
> > + sizeof(struct bio_vec) * BIO_INLINE_VECS + extra_size;
> > struct kmem_cache *slab = NULL;
> > struct bio_slab *bslab;
> > unsigned int i, entry = -1;
>
> But we already accounted for those bytes at the end. The generic setup
> does:
>
> unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
> ...
> fs_bio_set = bioset_create(BIO_POOL_SIZE, 0, back_pad);
>
> But I notice that you are seeing this with bio-1, not bio-0. So this
> must be the one of the pools created by md/dm. Does this help?
>
> I'll probably rework this a bit, perhaps we should just hide the back
> padding functionality and force it to be used for vec inlining only.
> Then it becomes invisible to the users.
Something like this, I'll fold it into the original patch.
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index b6b1b80..3326750 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1060,7 +1060,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad_page_pool;
}
- cc->bs = bioset_create(MIN_IOS, 0, 0);
+ cc->bs = bioset_create(MIN_IOS, 0);
if (!cc->bs) {
ti->error = "Cannot allocate crypt bioset";
goto bad_bs;
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index eb518b8..a343385 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -56,7 +56,7 @@ struct dm_io_client *dm_io_client_create(unsigned num_pages)
if (!client->pool)
goto bad;
- client->bios = bioset_create(16, 0, 0);
+ client->bios = bioset_create(16, 0);
if (!client->bios)
goto bad;
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 35975a4..368ffa3 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1091,7 +1091,7 @@ static struct mapped_device *alloc_dev(int minor)
if (!md->tio_pool)
goto bad_tio_pool;
- md->bs = bioset_create(16, 0, 0);
+ md->bs = bioset_create(16, 0);
if (!md->bs)
goto bad_no_bioset;
diff --git a/fs/bio.c b/fs/bio.c
index b4008e3..45ddca4 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1519,19 +1519,18 @@ void bioset_free(struct bio_set *bs)
* bioset_create - Create a bio_set
* @pool_size: Number of bio and bio_vecs to cache in the mempool
* @front_pad: Number of bytes to allocate in front of the returned bio
- * @back_pad: Number of bytes to allocate behind the returned bio
*
* Description:
* Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
- * to ask for a number of bytes to be allocated in front and back of the
- * bio. Front pad allocation is useful for embedding the bio inside
+ * to ask for a number of bytes to be allocated in front of the bio.
+ * Front pad allocation is useful for embedding the bio inside
* another structure, to avoid allocating extra data to go with the bio.
* Note that the bio must be embedded at the END of that structure always,
- * or things will break badly if back padding is also used.
+ * or things will break badly.
*/
-struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad,
- unsigned int back_pad)
+struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
{
+ unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
struct bio_set *bs;
bs = kzalloc(sizeof(*bs), GFP_KERNEL);
@@ -1584,8 +1583,6 @@ static void __init biovec_init_slabs(void)
static int __init init_bio(void)
{
- unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
-
bio_slab_max = 2;
bio_slab_nr = 0;
bio_slabs = kzalloc(bio_slab_max * sizeof(struct bio_slab), GFP_KERNEL);
@@ -1595,13 +1592,7 @@ static int __init init_bio(void)
bio_integrity_init_slab();
biovec_init_slabs();
- if (back_pad) {
- printk(KERN_INFO "bio: Using %d inlines, %u -> %u bytes\n",
- BIO_INLINE_VECS, (int) sizeof(struct bio),
- (int) sizeof(struct bio) + back_pad);
- }
-
- fs_bio_set = bioset_create(BIO_POOL_SIZE, 0, back_pad);
+ fs_bio_set = bioset_create(BIO_POOL_SIZE, 0);
if (!fs_bio_set)
panic("bio: can't allocate bios\n");
diff --git a/include/linux/bio.h b/include/linux/bio.h
index fbb62fb..76134d7 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -348,7 +348,7 @@ struct bio_pair {
extern struct bio_pair *bio_split(struct bio *bi, int first_sectors);
extern void bio_pair_release(struct bio_pair *dbio);
-extern struct bio_set *bioset_create(unsigned int, unsigned int, unsigned int);
+extern struct bio_set *bioset_create(unsigned int, unsigned int);
extern void bioset_free(struct bio_set *);
extern struct bio *bio_alloc(gfp_t, int);
--
Jens Axboe
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