btree_releasepage is a callback and can be passed unknown gfp flags and then they may end up in kmem_cache_alloc called from alloc_extent_state, slab allocator will BUG_ON when there is HIGHMEM or DMA32 flag set. This may happen when btrfs is mounted from a loop device, which masks out __GFP_IO flag. The check in try_release_extent_state 3399 if ((mask & GFP_NOFS) == GFP_NOFS) 3400 mask = GFP_NOFS; will not work and passes unfiltered flags further resulting in crash at mm/slab.c:2963 [<000000000024ae4c>] cache_alloc_refill+0x3b4/0x5c8 [<000000000024c810>] kmem_cache_alloc+0x204/0x294 [<00000000001fd3c2>] mempool_alloc+0x52/0x170 [<000003c000ced0b0>] alloc_extent_state+0x40/0xd4 [btrfs] [<000003c000cee5ae>] __clear_extent_bit+0x38a/0x4cc [btrfs] [<000003c000cee78c>] try_release_extent_state+0x9c/0xd4 [btrfs] [<000003c000cc4c66>] btree_releasepage+0x7e/0xd0 [btrfs] [<0000000000210d84>] shrink_page_list+0x6a0/0x724 [<0000000000211394>] shrink_inactive_list+0x230/0x578 [<0000000000211bb8>] shrink_list+0x6c/0x120 [<0000000000211e4e>] shrink_zone+0x1e2/0x228 [<0000000000211f24>] shrink_zones+0x90/0x254 [<0000000000213410>] do_try_to_free_pages+0xac/0x420 [<0000000000213ae0>] try_to_free_pages+0x13c/0x1b0 [<0000000000204e6c>] __alloc_pages_nodemask+0x5b4/0x9a8 [<00000000001fb04a>] grab_cache_page_write_begin+0x7e/0xe8 Signed-off-by: David Sterba <dsterba@suse.cz> --- fs/btrfs/disk-io.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index da4457f..4c86711 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -961,6 +961,13 @@ static int btree_releasepage(struct page *page, gfp_t gfp_flags) tree = &BTRFS_I(page->mapping->host)->io_tree; map = &BTRFS_I(page->mapping->host)->extent_tree; + /* + * We need to mask out eg. __GFP_HIGHMEM and __GFP_DMA32 as we''re doing + * slab allocation from alloc_extent_state down the callchain where + * it''d hit a BUG_ON as those flags are not allowed. + */ + gfp_flags &= ~GFP_SLAB_BUG_MASK; + ret = try_release_extent_state(map, tree, page, gfp_flags); if (!ret) return 0; -- 1.7.8 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[fixed the silly typo in subject] From: David Sterba <dsterba@suse.cz> btree_releasepage is a callback and can be passed unknown gfp flags and then they may end up in kmem_cache_alloc called from alloc_extent_state, slab allocator will BUG_ON when there is HIGHMEM or DMA32 flag set. This may happen when btrfs is mounted from a loop device, which masks out __GFP_IO flag. The check in try_release_extent_state 3399 if ((mask & GFP_NOFS) == GFP_NOFS) 3400 mask = GFP_NOFS; will not work and passes unfiltered flags further resulting in crash at mm/slab.c:2963 [<000000000024ae4c>] cache_alloc_refill+0x3b4/0x5c8 [<000000000024c810>] kmem_cache_alloc+0x204/0x294 [<00000000001fd3c2>] mempool_alloc+0x52/0x170 [<000003c000ced0b0>] alloc_extent_state+0x40/0xd4 [btrfs] [<000003c000cee5ae>] __clear_extent_bit+0x38a/0x4cc [btrfs] [<000003c000cee78c>] try_release_extent_state+0x9c/0xd4 [btrfs] [<000003c000cc4c66>] btree_releasepage+0x7e/0xd0 [btrfs] [<0000000000210d84>] shrink_page_list+0x6a0/0x724 [<0000000000211394>] shrink_inactive_list+0x230/0x578 [<0000000000211bb8>] shrink_list+0x6c/0x120 [<0000000000211e4e>] shrink_zone+0x1e2/0x228 [<0000000000211f24>] shrink_zones+0x90/0x254 [<0000000000213410>] do_try_to_free_pages+0xac/0x420 [<0000000000213ae0>] try_to_free_pages+0x13c/0x1b0 [<0000000000204e6c>] __alloc_pages_nodemask+0x5b4/0x9a8 [<00000000001fb04a>] grab_cache_page_write_begin+0x7e/0xe8 Signed-off-by: David Sterba <dsterba@suse.cz> --- fs/btrfs/disk-io.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index da4457f..4c86711 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -961,6 +961,13 @@ static int btree_releasepage(struct page *page, gfp_t gfp_flags) tree = &BTRFS_I(page->mapping->host)->io_tree; map = &BTRFS_I(page->mapping->host)->extent_tree; + /* + * We need to mask out eg. __GFP_HIGHMEM and __GFP_DMA32 as we''re doing + * slab allocation from alloc_extent_state down the callchain where + * it''d hit a BUG_ON as those flags are not allowed. + */ + gfp_flags &= ~GFP_SLAB_BUG_MASK; + ret = try_release_extent_state(map, tree, page, gfp_flags); if (!ret) return 0; -- 1.7.8 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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