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Date: Wed, 10 Dec 2008 15:11:09 +0100
From: Jens Axboe <jens.axboe@...cle.com>
To: Jiri Slaby <jirislaby@...il.com>
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org
Subject: Re: mmotm 2008-12-09-15-24: memory corruption (bio slab)
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.
diff --git a/fs/bio.c b/fs/bio.c
index b4008e3..ed9fc15 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -294,15 +294,20 @@ void bio_init(struct bio *bio)
**/
struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
{
+ unsigned int inline_vecs;
struct bio *bio = NULL;
if (bs) {
void *p = mempool_alloc(bs->bio_pool, gfp_mask);
- if (p)
+ if (p) {
bio = p + bs->front_pad;
- } else
+ inline_vecs = bs->inline_vecs;
+ }
+ } else {
bio = kmalloc(sizeof(*bio), gfp_mask);
+ inline_vecs = 0;
+ }
if (likely(bio)) {
struct bio_vec *bvl = NULL;
@@ -311,10 +316,10 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
if (likely(nr_iovecs)) {
unsigned long uninitialized_var(idx);
- if (nr_iovecs <= BIO_INLINE_VECS) {
+ if (nr_iovecs <= inline_vecs) {
idx = 0;
bvl = bio->bi_inline_vecs;
- nr_iovecs = BIO_INLINE_VECS;
+ nr_iovecs = inline_vecs;
} else {
bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx,
bs);
@@ -1605,6 +1610,8 @@ static int __init init_bio(void)
if (!fs_bio_set)
panic("bio: can't allocate bios\n");
+ fs_bio_set->inline_vecs = BIO_INLINE_VECS;
+
bio_split_pool = mempool_create_kmalloc_pool(BIO_SPLIT_ENTRIES,
sizeof(struct bio_pair));
if (!bio_split_pool)
diff --git a/include/linux/bio.h b/include/linux/bio.h
index fbb62fb..c9f8d26 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -417,6 +417,7 @@ static inline void bio_set_completion_cpu(struct bio *bio, unsigned int cpu)
struct bio_set {
struct kmem_cache *bio_slab;
unsigned int front_pad;
+ unsigned int inline_vecs;
mempool_t *bio_pool;
#if defined(CONFIG_BLK_DEV_INTEGRITY)
--
Jens Axboe
--
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