• Sergey Senozhatsky's avatar
    zram/zcomp: use GFP_NOIO to allocate streams · 3d5fe03a
    Sergey Senozhatsky authored
    We can end up allocating a new compression stream with GFP_KERNEL from
    within the IO path, which may result is nested (recursive) IO
    operations.  That can introduce problems if the IO path in question is a
    reclaimer, holding some locks that will deadlock nested IOs.
    
    Allocate streams and working memory using GFP_NOIO flag, forbidding
    recursive IO and FS operations.
    
    An example:
    
      inconsistent {IN-RECLAIM_FS-W} -> {RECLAIM_FS-ON-W} usage.
      git/20158 [HC0[0]:SC0[0]:HE1:SE1] takes:
       (jbd2_handle){+.+.?.}, at:  start_this_handle+0x4ca/0x555
      {IN-RECLAIM_FS-W} state was registered at:
         __lock_acquire+0x8da/0x117b
         lock_acquire+0x10c/0x1a7
         start_this_handle+0x52d/0x555
         jbd2__journal_start+0xb4/0x237
         __ext4_journal_start_sb+0x108/0x17e
         ext4_dirty_inode+0x32/0x61
         __mark_inode_dirty+0x16b/0x60c
         iput+0x11e/0x274
         __dentry_kill+0x148/0x1b8
         shrink_dentry_list+0x274/0x44a
         prune_dcache_sb+0x4a/0x55
         super_cache_scan+0xfc/0x176
         shrink_slab.part.14.constprop.25+0x2a2/0x4d3
         shrink_zone+0x74/0x140
         kswapd+0x6b7/0x930
         kthread+0x107/0x10f
         ret_from_fork+0x3f/0x70
      irq event stamp: 138297
      hardirqs last  enabled at (138297):  debug_check_no_locks_freed+0x113/0x12f
      hardirqs last disabled at (138296):  debug_check_no_locks_freed+0x33/0x12f
      softirqs last  enabled at (137818):  __do_softirq+0x2d3/0x3e9
      softirqs last disabled at (137813):  irq_exit+0x41/0x95
    
                   other info that might help us debug this:
       Possible unsafe locking scenario:
             CPU0
             ----
        lock(jbd2_handle);
        <Interrupt>
          lock(jbd2_handle);
    
                    *** DEADLOCK ***
      5 locks held by git/20158:
       #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff81155411>] mnt_want_write+0x24/0x4b
       #1:  (&type->i_mutex_dir_key#2/1){+.+.+.}, at: [<ffffffff81145087>] lock_rename+0xd9/0xe3
       #2:  (&sb->s_type->i_mutex_key#11){+.+.+.}, at: [<ffffffff8114f8e2>] lock_two_nondirectories+0x3f/0x6b
       #3:  (&sb->s_type->i_mutex_key#11/4){+.+.+.}, at: [<ffffffff8114f909>] lock_two_nondirectories+0x66/0x6b
       #4:  (jbd2_handle){+.+.?.}, at: [<ffffffff811e31db>] start_this_handle+0x4ca/0x555
    
                   stack backtrace:
      CPU: 2 PID: 20158 Comm: git Not tainted 4.1.0-rc7-next-20150615-dbg-00016-g8bdf555-dirty #211
      Call Trace:
        dump_stack+0x4c/0x6e
        mark_lock+0x384/0x56d
        mark_held_locks+0x5f/0x76
        lockdep_trace_alloc+0xb2/0xb5
        kmem_cache_alloc_trace+0x32/0x1e2
        zcomp_strm_alloc+0x25/0x73 [zram]
        zcomp_strm_multi_find+0xe7/0x173 [zram]
        zcomp_strm_find+0xc/0xe [zram]
        zram_bvec_rw+0x2ca/0x7e0 [zram]
        zram_make_request+0x1fa/0x301 [zram]
        generic_make_request+0x9c/0xdb
        submit_bio+0xf7/0x120
        ext4_io_submit+0x2e/0x43
        ext4_bio_write_page+0x1b7/0x300
        mpage_submit_page+0x60/0x77
        mpage_map_and_submit_buffers+0x10f/0x21d
        ext4_writepages+0xc8c/0xe1b
        do_writepages+0x23/0x2c
        __filemap_fdatawrite_range+0x84/0x8b
        filemap_flush+0x1c/0x1e
        ext4_alloc_da_blocks+0xb8/0x117
        ext4_rename+0x132/0x6dc
        ? mark_held_locks+0x5f/0x76
        ext4_rename2+0x29/0x2b
        vfs_rename+0x540/0x636
        SyS_renameat2+0x359/0x44d
        SyS_rename+0x1e/0x20
        entry_SYSCALL_64_fastpath+0x12/0x6f
    
    [minchan@kernel.org: add stable mark]
    Signed-off-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
    Acked-by: default avatarMinchan Kim <minchan@kernel.org>
    Cc: Kyeongdon Kim <kyeongdon.kim@lge.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    3d5fe03a
zcomp_lzo.c 1.11 KB