From: Wen Yang <[email protected]> The kworker has occupied 100% of the CPU for several days: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 68086 root 20 0 0 0 0 R 100.0 0.0 9718:18 kworker/u64:11
And the stack obtained through sysrq is as follows: [20613144.850426] task: ffff8800b5e08000 task.stack: ffffc9001342c000 [20613144.850427] RIP: 0010:[<ffffffffa0240743>] ^Ac [<ffffffffa0240743>] ext4_mb_discard_group_preallocations+0x1b3/0x480 [ext4] [20613144.850428] RSP: 0018:ffffc9001342f740 EFLAGS: 00000246 [20613144.850428] RAX: 0000000000000000 RBX: ffff8813bb5f72f0 RCX: 0000000000000000 [20613144.850429] RDX: 0000000000000001 RSI: ffff880268291d78 RDI: ffff880268291d98 [20613144.850430] RBP: ffffc9001342f7e8 R08: 00493b8bc070da84 R09: 0000000000000000 [20613144.850430] R10: 0000000000001800 R11: ffff880155e7c380 R12: ffff880268291d98 [20613144.850431] R13: ffff8813bb5f72e0 R14: ffff880268291d78 R15: ffff880268291d68 [20613144.850432] FS: 0000000000000000(0000) GS:ffff881fbf080000(0000) knlGS:0000000000000000 [20613144.850432] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [20613144.850433] CR2: 000000c000823010 CR3: 0000000001c08000 CR4: 00000000003606f0 [20613144.850434] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [20613144.850434] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [20613144.850435] Stack: [20613144.850435] ffff881942d6a6e8^Ac ffff8813bb5f72d0^Ac 00000001a02427cf^Ac 0000000000000140^Ac [20613144.850436] ffff880f80618000^Ac 0000000000000000^Ac ffffc9001342f770^Ac ffffc9001342f770^Ac [20613144.850437] ffffea0056360dc0^Ac ffff88158d837000^Ac ffffea0045155f80^Ac ffff88114557e000^Ac [20613144.850438] Call Trace: [20613144.850439] [<ffffffffa0244209>] ext4_mb_new_blocks+0x429/0x550 [ext4] [20613144.850439] [<ffffffffa02389ae>] ext4_ext_map_blocks+0xb5e/0xf30 [ext4] [20613144.850440] [<ffffffff811c0001>] ? numa_zonelist_order_handler+0xa1/0x1c0 [20613144.850441] [<ffffffffa0204b52>] ext4_map_blocks+0x172/0x620 [ext4] [20613144.850441] [<ffffffffa020835d>] ? ext4_writepages+0x4cd/0xf00 [ext4] [20613144.850442] [<ffffffffa0208675>] ext4_writepages+0x7e5/0xf00 [ext4] [20613144.850442] [<ffffffff811c1410>] ? wb_position_ratio+0x1f0/0x1f0 [20613144.850443] [<ffffffff811c487e>] do_writepages+0x1e/0x30 [20613144.850444] [<ffffffff81280265>] __writeback_single_inode+0x45/0x320 [20613144.850444] [<ffffffff81280ab2>] writeback_sb_inodes+0x272/0x600 [20613144.850445] [<ffffffff81280ed2>] __writeback_inodes_wb+0x92/0xc0 [20613144.850445] [<ffffffff81281238>] wb_writeback+0x268/0x300 [20613144.850446] [<ffffffff812819f4>] wb_workfn+0xb4/0x380 [20613144.850447] [<ffffffff810a5dc9>] process_one_work+0x189/0x420 [20613144.850447] [<ffffffff810a60ae>] worker_thread+0x4e/0x4b0 [20613144.850448] [<ffffffff810a6060>] ? process_one_work+0x420/0x420 [20613144.850448] [<ffffffff810ac696>] kthread+0xe6/0x100 [20613144.850449] [<ffffffff810ac5b0>] ? kthread_park+0x60/0x60 [20613144.850450] [<ffffffff81741dd9>] ret_from_fork+0x39/0x50 The cpu resources of the cloud server are precious, and the server cannot be restarted after running for a long time, so a configuration parameter is added to prevent this endless loop. Signed-off-by: Wen Yang <[email protected]> Cc: "Theodore Ts'o" <[email protected]> Cc: Andreas Dilger <[email protected]> Cc: Baoyou Xie <[email protected]> Cc: [email protected] Cc: [email protected] --- fs/ext4/ext4.h | 1 + fs/ext4/mballoc.c | 19 +++++++++++++++---- fs/ext4/mballoc.h | 2 ++ fs/ext4/sysfs.c | 2 ++ 4 files changed, 20 insertions(+), 4 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 2866d24..c238fec 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1543,6 +1543,7 @@ struct ext4_sb_info { unsigned long s_mb_last_start; unsigned int s_mb_prefetch; unsigned int s_mb_prefetch_limit; + unsigned long s_mb_max_retries_per_group; /* stats for buddy allocator */ atomic_t s_bal_reqs; /* number of reqs with len > 1 */ diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 99bf091..c126b15 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2853,6 +2853,8 @@ int ext4_mb_init(struct super_block *sb) sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD; sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS; sbi->s_mb_max_inode_prealloc = MB_DEFAULT_MAX_INODE_PREALLOC; + sbi->s_mb_max_retries_per_group = MB_DISCARD_RETRIES_FOREVER; + /* * The default group preallocation is 512, which for 4k block * sizes translates to 2 megabytes. However for bigalloc file @@ -4206,6 +4208,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac) ext4_group_t group, int needed) { struct ext4_group_info *grp = ext4_get_group_info(sb, group); + struct ext4_sb_info *sbi = EXT4_SB(sb); struct buffer_head *bitmap_bh = NULL; struct ext4_prealloc_space *pa, *tmp; struct list_head list; @@ -4213,6 +4216,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac) int err; int busy = 0; int free, free_total = 0; + int discard_retries = 0; mb_debug(sb, "discard preallocation for group %u\n", group); if (list_empty(&grp->bb_prealloc_list)) @@ -4291,11 +4295,18 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac) /* if we still need more blocks and some PAs were used, try again */ if (free_total < needed && busy) { - ext4_unlock_group(sb, group); - cond_resched(); - busy = 0; - goto repeat; + ++discard_retries; + if (sbi && sbi->s_mb_max_retries_per_group < discard_retries) { + ext4_warning(sb, "The retry count has exceeded the limit: %lu", + sbi->s_mb_max_retries_per_group); + } else { + ext4_unlock_group(sb, group); + cond_resched(); + busy = 0; + goto repeat; + } } + ext4_unlock_group(sb, group); ext4_mb_unload_buddy(&e4b); put_bh(bitmap_bh); diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h index e75b474..fa5b5a3 100644 --- a/fs/ext4/mballoc.h +++ b/fs/ext4/mballoc.h @@ -78,6 +78,8 @@ */ #define MB_DEFAULT_MAX_INODE_PREALLOC 512 +#define MB_DISCARD_RETRIES_FOREVER (-1UL) + struct ext4_free_data { /* this links the free block information from sb_info */ struct list_head efd_list; diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c index 075aa3a..3549520 100644 --- a/fs/ext4/sysfs.c +++ b/fs/ext4/sysfs.c @@ -213,6 +213,7 @@ static ssize_t journal_task_show(struct ext4_sb_info *sbi, char *buf) EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request); EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc); EXT4_RW_ATTR_SBI_UI(mb_max_inode_prealloc, s_mb_max_inode_prealloc); +EXT4_RW_ATTR_SBI_UL(mb_max_retries_per_group, s_mb_max_retries_per_group); EXT4_RW_ATTR_SBI_UI(extent_max_zeroout_kb, s_extent_max_zeroout_kb); EXT4_ATTR(trigger_fs_error, 0200, trigger_test_error); EXT4_RW_ATTR_SBI_UI(err_ratelimit_interval_ms, s_err_ratelimit_state.interval); @@ -260,6 +261,7 @@ static ssize_t journal_task_show(struct ext4_sb_info *sbi, char *buf) ATTR_LIST(mb_stream_req), ATTR_LIST(mb_group_prealloc), ATTR_LIST(mb_max_inode_prealloc), + ATTR_LIST(mb_max_retries_per_group), ATTR_LIST(max_writeback_mb_bump), ATTR_LIST(extent_max_zeroout_kb), ATTR_LIST(trigger_fs_error), -- 1.8.3.1
