[RFC 5/8] ext4: Do not fail journal due to block allocator
From: Michal Hocko mho...@suse.com Since mm: page_alloc: do not lock up GFP_NOFS allocations upon OOM memory allocator doesn't endlessly loop to satisfy low-order allocations and instead fails them to allow callers to handle them gracefully. Some of the callers are not yet prepared for this behavior though. ext4 block allocator relies solely on GFP_NOFS allocation requests and allocation failures lead to aborting yournal too easily: [ 345.028333] oom-trash: page allocation failure: order:0, mode:0x50 [ 345.028336] CPU: 1 PID: 8334 Comm: oom-trash Tainted: GW 4.0.0-nofs3-6-gdfe9931f5f68 #588 [ 345.028337] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150428_134905-gandalf 04/01/2014 [ 345.028339] 880005a17708 81538a54 8107a40f [ 345.028341] 0050 880005a17798 810fe854 00018000 [ 345.028342] 0046 81a52100 0246 [ 345.028343] Call Trace: [ 345.028348] [81538a54] dump_stack+0x4f/0x7b [ 345.028370] [810fe854] warn_alloc_failed+0x12a/0x13f [ 345.028373] [81101bd2] __alloc_pages_nodemask+0x7f3/0x8aa [ 345.028375] [810f9933] pagecache_get_page+0x12a/0x1c9 [ 345.028390] [a005bc64] ext4_mb_load_buddy+0x220/0x367 [ext4] [ 345.028414] [a006014f] ext4_free_blocks+0x522/0xa4c [ext4] [ 345.028425] [a0054e14] ext4_ext_remove_space+0x833/0xf22 [ext4] [ 345.028434] [a005677e] ext4_ext_truncate+0x8c/0xb0 [ext4] [ 345.028441] [a00342bf] ext4_truncate+0x20b/0x38d [ext4] [ 345.028462] [a003573c] ext4_evict_inode+0x32b/0x4c1 [ext4] [ 345.028464] [8116d04f] evict+0xa0/0x148 [ 345.028466] [8116dca8] iput+0x1a1/0x1f0 [ 345.028468] [811697b4] __dentry_kill+0x136/0x1a6 [ 345.028470] [81169a3e] dput+0x21a/0x243 [ 345.028472] [81157cda] __fput+0x184/0x19b [ 345.028473] [81157d29] fput+0xe/0x10 [ 345.028475] [8105a05f] task_work_run+0x8a/0xa1 [ 345.028477] [810452f0] do_exit+0x3c6/0x8dc [ 345.028482] [8104588a] do_group_exit+0x4d/0xb2 [ 345.028483] [8104eeeb] get_signal+0x5b1/0x5f5 [ 345.028488] [81002202] do_signal+0x28/0x5d0 [...] [ 345.028624] EXT4-fs error (device hdb1) in ext4_free_blocks:4879: Out of memory [ 345.033097] Aborting journal on device hdb1-8. [ 345.036339] EXT4-fs (hdb1): Remounting filesystem read-only [ 345.036344] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted [ 345.036766] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted [ 345.038583] EXT4-fs error (device hdb1) in ext4_ext_remove_space:3048: Journal has aborted [ 345.049115] EXT4-fs error (device hdb1) in ext4_ext_truncate:4669: Journal has aborted [ 345.050434] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted [ 345.053064] EXT4-fs error (device hdb1) in ext4_truncate:3668: Journal has aborted [ 345.053582] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted [ 345.053946] EXT4-fs error (device hdb1) in ext4_orphan_del:2686: Journal has aborted [ 345.055367] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted The failure is really premature because GFP_NOFS allocation context is very restricted - especially in the fs metadata heavy loads. Before we go with a more sofisticated solution, let's simply imitate the previous behavior of non-failing NOFS allocation and use __GFP_NOFAIL for the buddy block allocator. I wasn't able to trigger the issue with this patch anymore. Signed-off-by: Michal Hocko mho...@suse.com --- fs/ext4/mballoc.c | 12 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 5b1613a54307..e6361622bfd5 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -992,7 +992,8 @@ static int ext4_mb_get_buddy_page_lock(struct super_block *sb, block = group * 2; pnum = block / blocks_per_page; poff = block % blocks_per_page; - page = find_or_create_page(inode-i_mapping, pnum, GFP_NOFS); + page = find_or_create_page(inode-i_mapping, pnum, + GFP_NOFS|__GFP_NOFAIL); if (!page) return -ENOMEM; BUG_ON(page-mapping != inode-i_mapping); @@ -1006,7 +1007,8 @@ static int ext4_mb_get_buddy_page_lock(struct super_block *sb, block++; pnum = block / blocks_per_page; - page = find_or_create_page(inode-i_mapping, pnum, GFP_NOFS); + page = find_or_create_page(inode-i_mapping, pnum, + GFP_NOFS|__GFP_NOFAIL); if (!page) return -ENOMEM; BUG_ON(page-mapping != inode-i_mapping); @@ -1158,7 +1160,8 @@ ext4_mb_load_buddy(struct super_block *sb,
Re: [RFC 5/8] ext4: Do not fail journal due to block allocator
On Wed 05-08-15 11:51:21, mho...@kernel.org wrote: From: Michal Hocko mho...@suse.com Since mm: page_alloc: do not lock up GFP_NOFS allocations upon OOM memory allocator doesn't endlessly loop to satisfy low-order allocations and instead fails them to allow callers to handle them gracefully. Some of the callers are not yet prepared for this behavior though. ext4 block allocator relies solely on GFP_NOFS allocation requests and allocation failures lead to aborting yournal too easily: [ 345.028333] oom-trash: page allocation failure: order:0, mode:0x50 [ 345.028336] CPU: 1 PID: 8334 Comm: oom-trash Tainted: GW 4.0.0-nofs3-6-gdfe9931f5f68 #588 [ 345.028337] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150428_134905-gandalf 04/01/2014 [ 345.028339] 880005a17708 81538a54 8107a40f [ 345.028341] 0050 880005a17798 810fe854 00018000 [ 345.028342] 0046 81a52100 0246 [ 345.028343] Call Trace: [ 345.028348] [81538a54] dump_stack+0x4f/0x7b [ 345.028370] [810fe854] warn_alloc_failed+0x12a/0x13f [ 345.028373] [81101bd2] __alloc_pages_nodemask+0x7f3/0x8aa [ 345.028375] [810f9933] pagecache_get_page+0x12a/0x1c9 [ 345.028390] [a005bc64] ext4_mb_load_buddy+0x220/0x367 [ext4] [ 345.028414] [a006014f] ext4_free_blocks+0x522/0xa4c [ext4] [ 345.028425] [a0054e14] ext4_ext_remove_space+0x833/0xf22 [ext4] [ 345.028434] [a005677e] ext4_ext_truncate+0x8c/0xb0 [ext4] [ 345.028441] [a00342bf] ext4_truncate+0x20b/0x38d [ext4] [ 345.028462] [a003573c] ext4_evict_inode+0x32b/0x4c1 [ext4] [ 345.028464] [8116d04f] evict+0xa0/0x148 [ 345.028466] [8116dca8] iput+0x1a1/0x1f0 [ 345.028468] [811697b4] __dentry_kill+0x136/0x1a6 [ 345.028470] [81169a3e] dput+0x21a/0x243 [ 345.028472] [81157cda] __fput+0x184/0x19b [ 345.028473] [81157d29] fput+0xe/0x10 [ 345.028475] [8105a05f] task_work_run+0x8a/0xa1 [ 345.028477] [810452f0] do_exit+0x3c6/0x8dc [ 345.028482] [8104588a] do_group_exit+0x4d/0xb2 [ 345.028483] [8104eeeb] get_signal+0x5b1/0x5f5 [ 345.028488] [81002202] do_signal+0x28/0x5d0 [...] [ 345.028624] EXT4-fs error (device hdb1) in ext4_free_blocks:4879: Out of memory [ 345.033097] Aborting journal on device hdb1-8. [ 345.036339] EXT4-fs (hdb1): Remounting filesystem read-only [ 345.036344] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted [ 345.036766] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted [ 345.038583] EXT4-fs error (device hdb1) in ext4_ext_remove_space:3048: Journal has aborted [ 345.049115] EXT4-fs error (device hdb1) in ext4_ext_truncate:4669: Journal has aborted [ 345.050434] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted [ 345.053064] EXT4-fs error (device hdb1) in ext4_truncate:3668: Journal has aborted [ 345.053582] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted [ 345.053946] EXT4-fs error (device hdb1) in ext4_orphan_del:2686: Journal has aborted [ 345.055367] EXT4-fs error (device hdb1) in ext4_reserve_inode_write:4834: Journal has aborted The failure is really premature because GFP_NOFS allocation context is very restricted - especially in the fs metadata heavy loads. Before we go with a more sofisticated solution, let's simply imitate the previous behavior of non-failing NOFS allocation and use __GFP_NOFAIL for the buddy block allocator. I wasn't able to trigger the issue with this patch anymore. The patch looks good. You can add: Reviewed-by: Jan Kara j...@suse.com Honza Signed-off-by: Michal Hocko mho...@suse.com --- fs/ext4/mballoc.c | 12 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 5b1613a54307..e6361622bfd5 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -992,7 +992,8 @@ static int ext4_mb_get_buddy_page_lock(struct super_block *sb, block = group * 2; pnum = block / blocks_per_page; poff = block % blocks_per_page; - page = find_or_create_page(inode-i_mapping, pnum, GFP_NOFS); + page = find_or_create_page(inode-i_mapping, pnum, +GFP_NOFS|__GFP_NOFAIL); if (!page) return -ENOMEM; BUG_ON(page-mapping != inode-i_mapping); @@ -1006,7 +1007,8 @@ static int ext4_mb_get_buddy_page_lock(struct super_block *sb, block++; pnum = block / blocks_per_page; - page = find_or_create_page(inode-i_mapping, pnum, GFP_NOFS); + page =
