Hi, I have the problem that too many delayed refs block a btrfs storage. I have one thread that does work:
[<ffffffff810a3956>] io_schedule+0x16/0x40 [<ffffffff8117bff6>] wait_on_page_bit+0x116/0x150 [<ffffffff81359b65>] read_extent_buffer_pages+0x1c5/0x290 [<ffffffff81329dcd>] btree_read_extent_buffer_pages+0x9d/0x100 [<ffffffff8132b262>] read_tree_block+0x32/0x50 [<ffffffff8130a810>] read_block_for_search.isra.30+0x120/0x2e0 [<ffffffff8130c865>] btrfs_search_slot+0x385/0x990 [<ffffffff8130e501>] btrfs_insert_empty_items+0x71/0xc0 [<ffffffff8131186b>] insert_extent_data_ref.isra.49+0x11b/0x2a0 [<ffffffff8131608e>] __btrfs_inc_extent_ref.isra.59+0x1ee/0x220 [<ffffffff813197d4>] __btrfs_run_delayed_refs+0x924/0x12c0 [<ffffffff8131d17a>] btrfs_run_delayed_refs+0x7a/0x260 [<ffffffff81332da4>] create_pending_snapshot+0x5e4/0xf00 [<ffffffff81333757>] create_pending_snapshots+0x97/0xc0 [<ffffffff81333e95>] btrfs_commit_transaction+0x395/0x930 [<ffffffff8136bcf6>] btrfs_mksubvol+0x4a6/0x4f0 [<ffffffff8136bec5>] btrfs_ioctl_snap_create_transid+0x185/0x190 [<ffffffff8136c064>] btrfs_ioctl_snap_create_v2+0x104/0x150 [<ffffffff8136f891>] btrfs_ioctl+0x5e1/0x23b0 [<ffffffff812231c2>] do_vfs_ioctl+0x92/0x5a0 [<ffffffff81223749>] SyS_ioctl+0x79/0x9 the others are in 'D' state e.g. with [<ffffffff81798b57>] call_rwsem_down_write_failed+0x17/0x30 [<ffffffff8121f04b>] filename_create+0x6b/0x150 [<ffffffff8121ffa4>] SyS_mkdir+0x44/0xe0 Slabtop shows 2423910 btrfs_delayed_ref_head structs, slowly decreasing. What I think is happening is that delayed refs are added without throttling them with btrfs_should_throttle_delayed_refs . Maybe by creating a snapshot of a file and then modifying it (some action that creates delayed refs, is not truncate which is already throttled and does not commit a transaction which is also throttled). Regards, Martin Raiber -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
