Dmitry Monakhov <dmonak...@openvz.org> writes: > If filesystem holds transaction open 'current->journal_info' it should not > performs memory allocations with __GFP_FS flag enabled otherwise this result > in fs > reentarance which lead to: > 1) reentrance to itself : deadlock or internal assertion failure due to > incorrect journal credits > 1) entrance to another fs: assertion faulure or silient corruption due to > incorrect journal I've run xfstests suite for ext4, xfs and btrfs and it is appeared that btrfs has number of issues with fs re-entrance
#BUG1: btrfs_create, btrfs_mknode, btrfs_synlink, etc
btrfs_create:
->btrfs_start_transaction
->btrfs_find_free_ino
->start_caching
->kthread_run -> try to allocate mem with GFP_KERNEL
I'm not expert in btrfs but it looks like this issue may be fixed easily by
moving
btrfs_find_free_ino out of transaction scope.
#BUG2 btrfs_ioctl_send create fake journal transaction
current->journal_info = BTRFS_SEND_TRANS_STUB
and then call vfs_write which performs various mem allocation
WARNING: CPU: 1 PID: 30532 at mm/page_alloc.c:2808
__alloc_pages_nodemask+0xca/0x65d()
Modules linked in:
CPU: 1 PID: 30532 Comm: btrfs Not tainted 3.18.0-rc2-00012-g9f89e906-dirty #219
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
0000000000000af8 ffff88007acd79d8 ffffffff816bc74b 0000000000000af8
0000000000000000 ffff88007acd7a18 ffffffff81086599 00000000000200d2
ffffffff81144d2d 00000000000200d2 0000000000000000 0000000000000000
Call Trace:
[<ffffffff816bc74b>] dump_stack+0x49/0x5e
[<ffffffff81086599>] warn_slowpath_common+0x81/0x9b
[<ffffffff81144d2d>] ? __alloc_pages_nodemask+0xca/0x65d
[<ffffffff810865cd>] warn_slowpath_null+0x1a/0x1c
[<ffffffff81144d2d>] __alloc_pages_nodemask+0xca/0x65d
[<ffffffff810bc9fa>] ? trace_hardirqs_on_caller+0x164/0x19b
[<ffffffff810bca3e>] ? trace_hardirqs_on+0xd/0xf
[<ffffffff811863d6>] ? pipe_write+0x40/0x419
[<ffffffff811863d6>] ? pipe_write+0x40/0x419
[<ffffffff8118658b>] pipe_write+0x1f5/0x419
[<ffffffff8117e80a>] new_sync_write+0x8a/0xb2
[<ffffffff8117fdb7>] vfs_write+0xb5/0x14d
[<ffffffff81375b9b>] write_buf+0x58/0x8e
[<ffffffff8137c382>] btrfs_ioctl_send+0x5fa/0xdf8
[<ffffffff810ab549>] ? sched_clock_local+0x1c/0x82
[<ffffffff810bc488>] ? mark_lock+0x2d/0x1ec
[<ffffffff810bdc0f>] ? __lock_acquire+0x3e8/0xf39
[<ffffffff810ab852>] ? sched_clock_cpu+0x8e/0xaa
[<ffffffff816c1d83>] ? _raw_spin_unlock_irqrestore+0x55/0x72
[<ffffffff8134f6f8>] btrfs_ioctl+0x1258/0x1420
[<ffffffff8104a9b1>] ? sched_clock+0x17/0x1b
[<ffffffff810ab549>] ? sched_clock_local+0x1c/0x82
[<ffffffff810ab852>] ? sched_clock_cpu+0x8e/0xaa
[<ffffffff8118e227>] do_vfs_ioctl+0x43f/0x485
[<ffffffff81197154>] ? __fget+0x8c/0x97
[<ffffffff8118e2c7>] SyS_ioctl+0x5a/0x7f
[<ffffffff816c2229>] system_call_fastpath+0x12/0x17
>
> Signed-off-by: Dmitry Monakhov <dmonak...@openvz.org>
> ---
> include/linux/kernel.h | 7 +++++++
> mm/dmapool.c | 1 +
> mm/mempool.c | 1 +
> mm/page_alloc.c | 1 +
> mm/slab.c | 1 +
> mm/slub.c | 1 +
> 6 files changed, 12 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 3d770f5..69923d4 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -232,6 +232,13 @@ void might_fault(void);
> static inline void might_fault(void) { }
> #endif
>
> +#ifdef CONFIG_PROVE_LOCKING
> +#define might_enter_fs_if(cond) \
> + WARN_ON_ONCE((cond) && current->journal_info)
> +#else
> +static inline void might_enter_fs_if(bool cond) { }
> +#endif
> +
> extern struct atomic_notifier_head panic_notifier_list;
> extern long (*panic_blink)(int state);
> __printf(1, 2)
> diff --git a/mm/dmapool.c b/mm/dmapool.c
> index fd5fe43..c543eb8 100644
> --- a/mm/dmapool.c
> +++ b/mm/dmapool.c
> @@ -324,6 +324,7 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t
> mem_flags,
> void *retval;
>
> might_sleep_if(mem_flags & __GFP_WAIT);
> + might_enter_fs_if(mem_flags & __GFP_FS);
>
> spin_lock_irqsave(&pool->lock, flags);
> list_for_each_entry(page, &pool->page_list, page_list) {
> diff --git a/mm/mempool.c b/mm/mempool.c
> index e209c98..b5bb86f 100644
> --- a/mm/mempool.c
> +++ b/mm/mempool.c
> @@ -204,6 +204,7 @@ void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
>
> VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
> might_sleep_if(gfp_mask & __GFP_WAIT);
> + might_enter_fs_if(gfp_mask & __GFP_FS);
>
> gfp_mask |= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */
> gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9cd36b8..284a699 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2805,6 +2805,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int
> order,
> lockdep_trace_alloc(gfp_mask);
>
> might_sleep_if(gfp_mask & __GFP_WAIT);
> + might_enter_fs_if(gfp_mask & __GFP_FS);
>
> if (should_fail_alloc_page(gfp_mask, order))
> return NULL;
> diff --git a/mm/slab.c b/mm/slab.c
> index eb2b2ea..43b0d2f 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -2844,6 +2844,7 @@ static inline void cache_alloc_debugcheck_before(struct
> kmem_cache *cachep,
> gfp_t flags)
> {
> might_sleep_if(flags & __GFP_WAIT);
> + might_enter_fs_if(flags & __GFP_FS);
> #if DEBUG
> kmem_flagcheck(cachep, flags);
> #endif
> diff --git a/mm/slub.c b/mm/slub.c
> index ae7b9f1..474fc53 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1238,6 +1238,7 @@ static inline int slab_pre_alloc_hook(struct kmem_cache
> *s, gfp_t flags)
> flags &= gfp_allowed_mask;
> lockdep_trace_alloc(flags);
> might_sleep_if(flags & __GFP_WAIT);
> + might_enter_fs_if(flags & __GFP_FS);
>
> return should_failslab(s->object_size, flags, s->flags);
> }
> --
> 1.7.1
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