From: Wang Shilong <[email protected]> While running balance, scrub, fsstress concurrently we hit the following kernel crash:
[56561.448845] BTRFS info (device sde): relocating block group 11005853696 flags 132 [56561.524077] BUG: unable to handle kernel NULL pointer dereference at 0000000000000078 [56561.524237] IP: [<ffffffffa038956d>] scrub_chunk.isra.12+0xdd/0x130 [btrfs] [56561.524297] PGD 9be28067 PUD 7f3dd067 PMD 0 [56561.524325] Oops: 0000 [#1] SMP [....] [56561.527237] Call Trace: [56561.527309] [<ffffffffa038980e>] scrub_enumerate_chunks+0x24e/0x490 [btrfs] [56561.527392] [<ffffffff810abe00>] ? abort_exclusive_wait+0x50/0xb0 [56561.527476] [<ffffffffa038add4>] btrfs_scrub_dev+0x1a4/0x530 [btrfs] [56561.527561] [<ffffffffa0368107>] btrfs_ioctl+0x13f7/0x2a90 [btrfs] [56561.527639] [<ffffffff811c82f0>] do_vfs_ioctl+0x2e0/0x4c0 [56561.527712] [<ffffffff8109c384>] ? vtime_account_user+0x54/0x60 [56561.527788] [<ffffffff810f768c>] ? __audit_syscall_entry+0x9c/0xf0 [56561.527870] [<ffffffff811c8551>] SyS_ioctl+0x81/0xa0 [56561.527941] [<ffffffff815707f7>] tracesys+0xdd/0xe2 [...] [56561.528304] RIP [<ffffffffa038956d>] scrub_chunk.isra.12+0xdd/0x130 [btrfs] [56561.528395] RSP <ffff88004c0f5be8> [56561.528454] CR2: 0000000000000078 This is because in btrfs_relocate_chunk(), we will free @bdev directly while scrub may still hold extent mapping, and may access freed memory. Fix this problem by wrapping freeing @bdev work into free_extent_map() which is based on reference count. Reported-by: Qu Wenruo <[email protected]> Signed-off-by: Wang Shilong <[email protected]> --- fs/btrfs/extent_map.c | 2 ++ fs/btrfs/extent_map.h | 1 + fs/btrfs/volumes.c | 10 +++------- 3 files changed, 6 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 1874aee..225302b 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -75,6 +75,8 @@ void free_extent_map(struct extent_map *em) if (atomic_dec_and_test(&em->refs)) { WARN_ON(extent_map_in_tree(em)); WARN_ON(!list_empty(&em->list)); + if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags)) + kfree(em->bdev); kmem_cache_free(extent_map_cache, em); } } diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h index e7fd8a5..b2991fd 100644 --- a/fs/btrfs/extent_map.h +++ b/fs/btrfs/extent_map.h @@ -15,6 +15,7 @@ #define EXTENT_FLAG_PREALLOC 3 /* pre-allocated extent */ #define EXTENT_FLAG_LOGGING 4 /* Logging this extent */ #define EXTENT_FLAG_FILLING 5 /* Filling in a preallocated extent */ +#define EXTENT_FLAG_FS_MAPPING 6 /* filesystem extent mapping type */ struct extent_map { struct rb_node rb_node; diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 49d7fab..a7b9e85 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2490,9 +2490,6 @@ static int btrfs_relocate_chunk(struct btrfs_root *root, remove_extent_mapping(em_tree, em); write_unlock(&em_tree->lock); - kfree(map); - em->bdev = NULL; - /* once for the tree */ free_extent_map(em); /* once for us */ @@ -4213,9 +4210,11 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans, em = alloc_extent_map(); if (!em) { + kfree(map); ret = -ENOMEM; goto error; } + set_bit(EXTENT_FLAG_FS_MAPPING, &em->flags); em->bdev = (struct block_device *)map; em->start = start; em->len = num_bytes; @@ -4258,7 +4257,6 @@ error_del_extent: /* One for the tree reference */ free_extent_map(em); error: - kfree(map); kfree(devices_info); return ret; } @@ -4470,7 +4468,6 @@ void btrfs_mapping_tree_free(struct btrfs_mapping_tree *tree) write_unlock(&tree->map_tree.lock); if (!em) break; - kfree(em->bdev); /* once for us */ free_extent_map(em); /* once for the tree */ @@ -5734,6 +5731,7 @@ static int read_one_chunk(struct btrfs_root *root, struct btrfs_key *key, return -ENOMEM; } + set_bit(EXTENT_FLAG_FS_MAPPING, &em->flags); em->bdev = (struct block_device *)map; em->start = logical; em->len = length; @@ -5758,7 +5756,6 @@ static int read_one_chunk(struct btrfs_root *root, struct btrfs_key *key, map->stripes[i].dev = btrfs_find_device(root->fs_info, devid, uuid, NULL); if (!map->stripes[i].dev && !btrfs_test_opt(root, DEGRADED)) { - kfree(map); free_extent_map(em); return -EIO; } @@ -5766,7 +5763,6 @@ static int read_one_chunk(struct btrfs_root *root, struct btrfs_key *key, map->stripes[i].dev = add_missing_dev(root, devid, uuid); if (!map->stripes[i].dev) { - kfree(map); free_extent_map(em); return -EIO; } -- 1.9.2 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
