kernel.git/fs/btrfs/backref.c, branch linux-3.18.y

Btrfs: fix hang on extent buffer lock caused by the inode_paths ioctl

2016-03-02T20:18:57Z

[ Upstream commit 0c0fe3b0fa45082cd752553fdb3a4b42503a118e ] While doing some tests I ran into an hang on an extent buffer's rwlock that produced the following trace: [39389.800012] NMI watchdog: BUG: soft lockup - CPU#15 stuck for 22s! [fdm-stress:32166] [39389.800016] NMI watchdog: BUG: soft lockup - CPU#14 stuck for 22s! [fdm-stress:32165] [39389.800016] Modules linked in: btrfs dm_mod ppdev xor sha256_generic hmac raid6_pq drbg ansi_cprng aesni_intel i2c_piix4 acpi_cpufreq aes_x86_64 ablk_helper tpm_tis parport_pc i2c_core sg cryptd evdev psmouse lrw tpm parport gf128mul serio_raw pcspkr glue_helper processor button loop autofs4 ext4 crc16 mbcache jbd2 sd_mod sr_mod cdrom ata_generic virtio_scsi ata_piix libata virtio_pci virtio_ring crc32c_intel scsi_mod e1000 virtio floppy [last unloaded: btrfs] [39389.800016] irq event stamp: 0 [39389.800016] hardirqs last enabled at (0): [< (null)>] (null) [39389.800016] hardirqs last disabled at (0): [] copy_process+0x638/0x1a35 [39389.800016] softirqs last enabled at (0): [] copy_process+0x638/0x1a35 [39389.800016] softirqs last disabled at (0): [< (null)>] (null) [39389.800016] CPU: 14 PID: 32165 Comm: fdm-stress Not tainted 4.4.0-rc6-btrfs-next-18+ #1 [39389.800016] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS by qemu-project.org 04/01/2014 [39389.800016] task: ffff880175b1ca40 ti: ffff8800a185c000 task.ti: ffff8800a185c000 [39389.800016] RIP: 0010:[] [] queued_spin_lock_slowpath+0x57/0x158 [39389.800016] RSP: 0018:ffff8800a185fb80 EFLAGS: 00000202 [39389.800016] RAX: 0000000000000101 RBX: ffff8801710c4e9c RCX: 0000000000000101 [39389.800016] RDX: 0000000000000100 RSI: 0000000000000001 RDI: 0000000000000001 [39389.800016] RBP: ffff8800a185fb98 R08: 0000000000000001 R09: 0000000000000000 [39389.800016] R10: ffff8800a185fb68 R11: 6db6db6db6db6db7 R12: ffff8801710c4e98 [39389.800016] R13: ffff880175b1ca40 R14: ffff8800a185fc10 R15: ffff880175b1ca40 [39389.800016] FS: 00007f6d37fff700(0000) GS:ffff8802be9c0000(0000) knlGS:0000000000000000 [39389.800016] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [39389.800016] CR2: 00007f6d300019b8 CR3: 0000000037c93000 CR4: 00000000001406e0 [39389.800016] Stack: [39389.800016] ffff8801710c4e98 ffff8801710c4e98 ffff880175b1ca40 ffff8800a185fbb0 [39389.800016] ffffffff81091e11 ffff8801710c4e98 ffff8800a185fbc8 ffffffff81091895 [39389.800016] ffff8801710c4e98 ffff8800a185fbe8 ffffffff81486c5c ffffffffa067288c [39389.800016] Call Trace: [39389.800016] [] queued_read_lock_slowpath+0x46/0x60 [39389.800016] [] do_raw_read_lock+0x3e/0x41 [39389.800016] [] _raw_read_lock+0x3d/0x44 [39389.800016] [] ? btrfs_tree_read_lock+0x54/0x125 [btrfs] [39389.800016] [] btrfs_tree_read_lock+0x54/0x125 [btrfs] [39389.800016] [] ? btrfs_find_item+0xa7/0xd2 [btrfs] [39389.800016] [] btrfs_ref_to_path+0xd6/0x174 [btrfs] [39389.800016] [] inode_to_path+0x53/0xa2 [btrfs] [39389.800016] [] paths_from_inode+0x117/0x2ec [btrfs] [39389.800016] [] btrfs_ioctl+0xd5b/0x2793 [btrfs] [39389.800016] [] ? arch_local_irq_save+0x9/0xc [39389.800016] [] ? __this_cpu_preempt_check+0x13/0x15 [39389.800016] [] ? arch_local_irq_save+0x9/0xc [39389.800016] [] ? rcu_read_unlock+0x3e/0x5d [39389.800016] [] do_vfs_ioctl+0x42b/0x4ea [39389.800016] [] ? __fget_light+0x62/0x71 [39389.800016] [] SyS_ioctl+0x57/0x79 [39389.800016] [] entry_SYSCALL_64_fastpath+0x12/0x6f [39389.800016] Code: b9 01 01 00 00 f7 c6 00 ff ff ff 75 32 83 fe 01 89 ca 89 f0 0f 45 d7 f0 0f b1 13 39 f0 74 04 89 c6 eb e2 ff ca 0f 84 fa 00 00 00 <8b> 03 84 c0 74 04 f3 90 eb f6 66 c7 03 01 00 e9 e6 00 00 00 e8 [39389.800012] Modules linked in: btrfs dm_mod ppdev xor sha256_generic hmac raid6_pq drbg ansi_cprng aesni_intel i2c_piix4 acpi_cpufreq aes_x86_64 ablk_helper tpm_tis parport_pc i2c_core sg cryptd evdev psmouse lrw tpm parport gf128mul serio_raw pcspkr glue_helper processor button loop autofs4 ext4 crc16 mbcache jbd2 sd_mod sr_mod cdrom ata_generic virtio_scsi ata_piix libata virtio_pci virtio_ring crc32c_intel scsi_mod e1000 virtio floppy [last unloaded: btrfs] [39389.800012] irq event stamp: 0 [39389.800012] hardirqs last enabled at (0): [< (null)>] (null) [39389.800012] hardirqs last disabled at (0): [] copy_process+0x638/0x1a35 [39389.800012] softirqs last enabled at (0): [] copy_process+0x638/0x1a35 [39389.800012] softirqs last disabled at (0): [< (null)>] (null) [39389.800012] CPU: 15 PID: 32166 Comm: fdm-stress Tainted: G L 4.4.0-rc6-btrfs-next-18+ #1 [39389.800012] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS by qemu-project.org 04/01/2014 [39389.800012] task: ffff880179294380 ti: ffff880034a60000 task.ti: ffff880034a60000 [39389.800012] RIP: 0010:[] [] queued_write_lock_slowpath+0x62/0x72 [39389.800012] RSP: 0018:ffff880034a639f0 EFLAGS: 00000206 [39389.800012] RAX: 0000000000000101 RBX: ffff8801710c4e98 RCX: 0000000000000000 [39389.800012] RDX: 00000000000000ff RSI: 0000000000000000 RDI: ffff8801710c4e9c [39389.800012] RBP: ffff880034a639f8 R08: 0000000000000001 R09: 0000000000000000 [39389.800012] R10: ffff880034a639b0 R11: 0000000000001000 R12: ffff8801710c4e98 [39389.800012] R13: 0000000000000001 R14: ffff880172cbc000 R15: ffff8801710c4e00 [39389.800012] FS: 00007f6d377fe700(0000) GS:ffff8802be9e0000(0000) knlGS:0000000000000000 [39389.800012] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [39389.800012] CR2: 00007f6d3d3c1000 CR3: 0000000037c93000 CR4: 00000000001406e0 [39389.800012] Stack: [39389.800012] ffff8801710c4e98 ffff880034a63a10 ffffffff81091963 ffff8801710c4e98 [39389.800012] ffff880034a63a30 ffffffff81486f1b ffffffffa0672cb3 ffff8801710c4e00 [39389.800012] ffff880034a63a78 ffffffffa0672cb3 ffff8801710c4e00 ffff880034a63a58 [39389.800012] Call Trace: [39389.800012] [] do_raw_write_lock+0x72/0x8c [39389.800012] [] _raw_write_lock+0x3a/0x41 [39389.800012] [] ? btrfs_tree_lock+0x119/0x251 [btrfs] [39389.800012] [] btrfs_tree_lock+0x119/0x251 [btrfs] [39389.800012] [] ? rcu_read_unlock+0x5b/0x5d [btrfs] [39389.800012] [] ? btrfs_root_node+0xda/0xe6 [btrfs] [39389.800012] [] btrfs_lock_root_node+0x22/0x42 [btrfs] [39389.800012] [] btrfs_search_slot+0x1b8/0x758 [btrfs] [39389.800012] [] ? time_hardirqs_on+0x15/0x28 [39389.800012] [] btrfs_lookup_inode+0x31/0x95 [btrfs] [39389.800012] [] ? trace_hardirqs_on+0xd/0xf [39389.800012] [] ? mutex_lock_nested+0x397/0x3bc [39389.800012] [] __btrfs_update_delayed_inode+0x59/0x1c0 [btrfs] [39389.800012] [] __btrfs_commit_inode_delayed_items+0x194/0x5aa [btrfs] [39389.800012] [] ? _raw_spin_unlock+0x31/0x44 [39389.800012] [] __btrfs_run_delayed_items+0xa4/0x15c [btrfs] [39389.800012] [] btrfs_run_delayed_items+0x11/0x13 [btrfs] [39389.800012] [] btrfs_commit_transaction+0x234/0x96e [btrfs] [39389.800012] [] btrfs_sync_fs+0x145/0x1ad [btrfs] [39389.800012] [] btrfs_ioctl+0x11d2/0x2793 [btrfs] [39389.800012] [] ? arch_local_irq_save+0x9/0xc [39389.800012] [] ? __might_fault+0x4c/0xa7 [39389.800012] [] ? __might_fault+0x4c/0xa7 [39389.800012] [] ? arch_local_irq_save+0x9/0xc [39389.800012] [] ? rcu_read_unlock+0x3e/0x5d [39389.800012] [] do_vfs_ioctl+0x42b/0x4ea [39389.800012] [] ? __fget_light+0x62/0x71 [39389.800012] [] SyS_ioctl+0x57/0x79 [39389.800012] [] entry_SYSCALL_64_fastpath+0x12/0x6f [39389.800012] Code: f0 0f b1 13 85 c0 75 ef eb 2a f3 90 8a 03 84 c0 75 f8 f0 0f b0 13 84 c0 75 f0 ba ff 00 00 00 eb 0a f0 0f b1 13 ff c8 74 0b f3 90 <8b> 03 83 f8 01 75 f7 eb ed c6 43 04 00 5b 5d c3 0f 1f 44 00 00 This happens because in the code path executed by the inode_paths ioctl we end up nesting two calls to read lock a leaf's rwlock when after the first call to read_lock() and before the second call to read_lock(), another task (running the delayed items as part of a transaction commit) has already called write_lock() against the leaf's rwlock. This situation is illustrated by the following diagram: Task A Task B btrfs_ref_to_path() btrfs_commit_transaction() read_lock(&eb->lock); btrfs_run_delayed_items() __btrfs_commit_inode_delayed_items() __btrfs_update_delayed_inode() btrfs_lookup_inode() write_lock(&eb->lock); --> task waits for lock read_lock(&eb->lock); --> makes this task hang forever (and task B too of course) So fix this by avoiding doing the nested read lock, which is easily avoidable. This issue does not happen if task B calls write_lock() after task A does the second call to read_lock(), however there does not seem to exist anything in the documentation that mentions what is the expected behaviour for recursive locking of rwlocks (leaving the idea that doing so is not a good usage of rwlocks). Also, as a side effect necessary for this fix, make sure we do not needlessly read lock extent buffers when the input path has skip_locking set (used when called from send). Cc: stable@vger.kernel.org Signed-off-by: Filipe Manana Signed-off-by: Sasha Levin

btrfs: fix use after free iterating extrefs

2015-11-13T18:18:11Z

[ Upstream commit dc6c5fb3b514221f2e9d21ee626a9d95d3418dff ] The code for btrfs inode-resolve has never worked properly for files with enough hard links to trigger extrefs. It was trying to get the leaf out of a path after freeing the path: btrfs_release_path(path); leaf = path->nodes[0]; item_size = btrfs_item_size_nr(leaf, slot); The fix here is to use the extent buffer we cloned just a little higher up to avoid deadlocks caused by using the leaf in the path. Signed-off-by: Chris Mason cc: stable@vger.kernel.org # v3.7+ cc: Mark Fasheh Reviewed-by: Filipe Manana Reviewed-by: Mark Fasheh Signed-off-by: Sasha Levin

btrfs: remove parameter blocksize from read_tree_block

2014-10-02T15:14:50Z

We know the tree block size, no need to pass it around. Signed-off-by: David Sterba

Btrfs: make fiemap not blow when you have lots of snapshots

2014-09-17T20:38:24Z

We have been iterating all references for each extent we have in a file when we do fiemap to see if it is shared. This is fine when you have a few clones or a few snapshots, but when you have 5k snapshots suddenly fiemap just sits there and stares at you. So add btrfs_check_shared which will use the backref walking code but will short circuit as soon as it finds a root or inode that doesn't match the one we currently have. This makes fiemap on my testbox go from looking at me blankly for a day to spitting out actual output in a reasonable amount of time. Thanks, Signed-off-by: Josef Bacik Signed-off-by: Chris Mason

btrfs: use nodesize everywhere, kill leafsize

2014-09-17T20:37:14Z

The nodesize and leafsize were never of different values. Unify the usage and make nodesize the one. Cleanup the redundant checks and helpers. Shaves a few bytes from .text: text data bss dec hex filename 852418 24560 23112 900090 dbbfa btrfs.ko.before 851074 24584 23112 898770 db6d2 btrfs.ko.after Signed-off-by: David Sterba Signed-off-by: Chris Mason

btrfs: kill the key type accessor helpers

2014-09-17T20:37:12Z

btrfs_set_key_type and btrfs_key_type are used inconsistently along with open coded variants. Other members of btrfs_key are accessed directly without any helpers anyway. Signed-off-by: David Sterba Signed-off-by: Chris Mason

Btrfs: Fix memory corruption by ulist_add_merge() on 32bit arch

2014-08-15T14:43:19Z

We've got bug reports that btrfs crashes when quota is enabled on 32bit kernel, typically with the Oops like below: BUG: unable to handle kernel NULL pointer dereference at 00000004 IP: [] find_parent_nodes+0x360/0x1380 [btrfs] *pde = 00000000 Oops: 0000 [#1] SMP CPU: 0 PID: 151 Comm: kworker/u8:2 Tainted: G S W 3.15.2-1.gd43d97e-default #1 Workqueue: btrfs-qgroup-rescan normal_work_helper [btrfs] task: f1478130 ti: f147c000 task.ti: f147c000 EIP: 0060:[] EFLAGS: 00010213 CPU: 0 EIP is at find_parent_nodes+0x360/0x1380 [btrfs] EAX: f147dda8 EBX: f147ddb0 ECX: 00000011 EDX: 00000000 ESI: 00000000 EDI: f147dda4 EBP: f147ddf8 ESP: f147dd38 DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 CR0: 8005003b CR2: 00000004 CR3: 00bf3000 CR4: 00000690 Stack: 00000000 00000000 f147dda4 00000050 00000001 00000000 00000001 00000050 00000001 00000000 d3059000 00000001 00000022 000000a8 00000000 00000000 00000000 000000a1 00000000 00000000 00000001 00000000 00000000 11800000 Call Trace: [] __btrfs_find_all_roots+0x9d/0xf0 [btrfs] [] btrfs_qgroup_rescan_worker+0x401/0x760 [btrfs] [] normal_work_helper+0xc8/0x270 [btrfs] [] process_one_work+0x11b/0x390 [] worker_thread+0x101/0x340 [] kthread+0x9b/0xb0 [] ret_from_kernel_thread+0x21/0x30 [] kthread_create_on_node+0x110/0x110 This indicates a NULL corruption in prefs_delayed list. The further investigation and bisection pointed that the call of ulist_add_merge() results in the corruption. ulist_add_merge() takes u64 as aux and writes a 64bit value into old_aux. The callers of this function in backref.c, however, pass a pointer of a pointer to old_aux. That is, the function overwrites 64bit value on 32bit pointer. This caused a NULL in the adjacent variable, in this case, prefs_delayed. Here is a quick attempt to band-aid over this: a new function, ulist_add_merge_ptr() is introduced to pass/store properly a pointer value instead of u64. There are still ugly void ** cast remaining in the callers because void ** cannot be taken implicitly. But, it's safer than explicit cast to u64, anyway. Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=887046 Cc: [v3.11+] Signed-off-by: Takashi Iwai Signed-off-by: Chris Mason

Btrfs: read lock extent buffer while walking backrefs

2014-08-15T14:43:13Z

Before processing the extent buffer, acquire a read lock on it, so that we're safe against concurrent updates on the extent buffer. Signed-off-by: Filipe Manana Signed-off-by: Chris Mason

Btrfs: fix scrub_print_warning to handle skinny metadata extents

2014-06-10T00:21:17Z

The skinny extents are intepreted incorrectly in scrub_print_warning(), and end up hitting the BUG() in btrfs_extent_inline_ref_size. Reported-by: Konstantinos Skarlatos Signed-off-by: Liu Bo Signed-off-by: Chris Mason

Btrfs: use right type to get real comparison

2014-06-10T00:21:15Z

We want to make sure the point is still within the extent item, not to verify the memory it's pointing to. Signed-off-by: Liu Bo Signed-off-by: Chris Mason