| Message ID | dd0cb649510537a495bc64d91e09da5a8119d2e3.1725950283.git.jth@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] btrfs: don't take dev_replace rwsem on task already holding it | expand |
This is to fold in if we decide to go by pid instead of a task_struct.
---
fs/btrfs/dev-replace.c | 4 ++--
fs/btrfs/fs.h | 3 ++-
fs/btrfs/volumes.c | 8 +++++---
3 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 604399e59a3d..a1efb8de8170 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -641,7 +641,7 @@ static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
return ret;
down_write(&dev_replace->rwsem);
- dev_replace->replace_task = current;
+ dev_replace->replace_task = current->pid;
switch (dev_replace->replace_state) {
case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
@@ -995,7 +995,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list);
fs_devices->rw_devices++;
- dev_replace->replace_task = NULL;
+ dev_replace->replace_task = 0;
up_write(&dev_replace->rwsem);
btrfs_rm_dev_replace_blocked(fs_info);
diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index cbfb225858a5..a30978f29a59 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -3,6 +3,7 @@
#ifndef BTRFS_FS_H
#define BTRFS_FS_H
+#include "linux/types.h"
#include <linux/blkdev.h>
#include <linux/sizes.h>
#include <linux/time64.h>
@@ -318,7 +319,7 @@ struct btrfs_dev_replace {
struct percpu_counter bio_counter;
wait_queue_head_t replace_wait;
- struct task_struct *replace_task;
+ pid_t replace_task;
};
/*
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 995b0647f538..c3f53a59cbf3 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6480,7 +6480,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
max_len = btrfs_max_io_len(map, map_offset, &io_geom);
*length = min_t(u64, map->chunk_len - map_offset, max_len);
- if (dev_replace->replace_task != current)
+ if (dev_replace->replace_task != current->pid)
down_read(&dev_replace->rwsem);
dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace);
@@ -6488,7 +6488,8 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
* Hold the semaphore for read during the whole operation, write is
* requested at commit time but must wait.
*/
- if (!dev_replace_is_ongoing && dev_replace->replace_task != current)
+ if (!dev_replace_is_ongoing &&
+ dev_replace->replace_task != current->pid)
up_read(&dev_replace->rwsem);
switch (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
@@ -6628,7 +6629,8 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
bioc->mirror_num = io_geom.mirror_num;
out:
- if (dev_replace_is_ongoing && dev_replace->replace_task != current) {
+ if (dev_replace_is_ongoing &&
+ dev_replace->replace_task != current->pid) {
lockdep_assert_held(&dev_replace->rwsem);
/* Unlock and let waiting writers proceed */
up_read(&dev_replace->rwsem);
On Tue, Sep 10, 2024 at 8:55 AM Johannes Thumshirn <jth@kernel.org> wrote: > > From: Johannes Thumshirn <johannes.thumshirn@wdc.com> > > Running fstests btrfs/011 with MKFS_OPTIONS="-O rst" to force the usage of > the RAID stripe-tree, we get the following splat from lockdep: > > BTRFS info (device sdd): dev_replace from /dev/sdd (devid 1) to /dev/sdb started > > ============================================ > WARNING: possible recursive locking detected > 6.11.0-rc3-btrfs-for-next #599 Not tainted > -------------------------------------------- > btrfs/2326 is trying to acquire lock: > ffff88810f215c98 (&fs_info->dev_replace.rwsem){++++}-{3:3}, at: btrfs_map_block+0x39f/0x2250 > > but task is already holding lock: > ffff88810f215c98 (&fs_info->dev_replace.rwsem){++++}-{3:3}, at: btrfs_map_block+0x39f/0x2250 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&fs_info->dev_replace.rwsem); > lock(&fs_info->dev_replace.rwsem); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 1 lock held by btrfs/2326: > #0: ffff88810f215c98 (&fs_info->dev_replace.rwsem){++++}-{3:3}, at: btrfs_map_block+0x39f/0x2250 > > stack backtrace: > CPU: 1 UID: 0 PID: 2326 Comm: btrfs Not tainted 6.11.0-rc3-btrfs-for-next #599 > Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > Call Trace: > <TASK> > dump_stack_lvl+0x5b/0x80 > __lock_acquire+0x2798/0x69d0 > ? __pfx___lock_acquire+0x10/0x10 > ? __pfx___lock_acquire+0x10/0x10 > lock_acquire+0x19d/0x4a0 > ? btrfs_map_block+0x39f/0x2250 > ? __pfx_lock_acquire+0x10/0x10 > ? find_held_lock+0x2d/0x110 > ? lock_is_held_type+0x8f/0x100 > down_read+0x8e/0x440 > ? btrfs_map_block+0x39f/0x2250 > ? __pfx_down_read+0x10/0x10 > ? do_raw_read_unlock+0x44/0x70 > ? _raw_read_unlock+0x23/0x40 > btrfs_map_block+0x39f/0x2250 > ? btrfs_dev_replace_by_ioctl+0xd69/0x1d00 > ? btrfs_bio_counter_inc_blocked+0xd9/0x2e0 > ? __kasan_slab_alloc+0x6e/0x70 > ? __pfx_btrfs_map_block+0x10/0x10 > ? __pfx_btrfs_bio_counter_inc_blocked+0x10/0x10 > ? kmem_cache_alloc_noprof+0x1f2/0x300 > ? mempool_alloc_noprof+0xed/0x2b0 > btrfs_submit_chunk+0x28d/0x17e0 > ? __pfx_btrfs_submit_chunk+0x10/0x10 > ? bvec_alloc+0xd7/0x1b0 > ? bio_add_folio+0x171/0x270 > ? __pfx_bio_add_folio+0x10/0x10 > ? __kasan_check_read+0x20/0x20 > btrfs_submit_bio+0x37/0x80 > read_extent_buffer_pages+0x3df/0x6c0 > btrfs_read_extent_buffer+0x13e/0x5f0 > read_tree_block+0x81/0xe0 > read_block_for_search+0x4bd/0x7a0 > ? __pfx_read_block_for_search+0x10/0x10 > btrfs_search_slot+0x78d/0x2720 > ? __pfx_btrfs_search_slot+0x10/0x10 > ? lock_is_held_type+0x8f/0x100 > ? kasan_save_track+0x14/0x30 > ? __kasan_slab_alloc+0x6e/0x70 > ? kmem_cache_alloc_noprof+0x1f2/0x300 > btrfs_get_raid_extent_offset+0x181/0x820 > ? __pfx_lock_acquire+0x10/0x10 > ? __pfx_btrfs_get_raid_extent_offset+0x10/0x10 > ? down_read+0x194/0x440 > ? __pfx_down_read+0x10/0x10 > ? do_raw_read_unlock+0x44/0x70 > ? _raw_read_unlock+0x23/0x40 > btrfs_map_block+0x5b5/0x2250 > ? __pfx_btrfs_map_block+0x10/0x10 > scrub_submit_initial_read+0x8fe/0x11b0 > ? __pfx_scrub_submit_initial_read+0x10/0x10 > submit_initial_group_read+0x161/0x3a0 > ? lock_release+0x20e/0x710 > ? __pfx_submit_initial_group_read+0x10/0x10 > ? __pfx_lock_release+0x10/0x10 > scrub_simple_mirror.isra.0+0x3eb/0x580 > scrub_stripe+0xe4d/0x1440 > ? lock_release+0x20e/0x710 > ? __pfx_scrub_stripe+0x10/0x10 > ? __pfx_lock_release+0x10/0x10 > ? do_raw_read_unlock+0x44/0x70 > ? _raw_read_unlock+0x23/0x40 > scrub_chunk+0x257/0x4a0 > scrub_enumerate_chunks+0x64c/0xf70 > ? __mutex_unlock_slowpath+0x147/0x5f0 > ? __pfx_scrub_enumerate_chunks+0x10/0x10 > ? bit_wait_timeout+0xb0/0x170 > ? __up_read+0x189/0x700 > ? scrub_workers_get+0x231/0x300 > ? up_write+0x490/0x4f0 > btrfs_scrub_dev+0x52e/0xcd0 > ? create_pending_snapshots+0x230/0x250 > ? __pfx_btrfs_scrub_dev+0x10/0x10 > btrfs_dev_replace_by_ioctl+0xd69/0x1d00 > ? lock_acquire+0x19d/0x4a0 > ? __pfx_btrfs_dev_replace_by_ioctl+0x10/0x10 > ? lock_release+0x20e/0x710 > ? btrfs_ioctl+0xa09/0x74f0 > ? __pfx_lock_release+0x10/0x10 > ? do_raw_spin_lock+0x11e/0x240 > ? __pfx_do_raw_spin_lock+0x10/0x10 > btrfs_ioctl+0xa14/0x74f0 > ? lock_acquire+0x19d/0x4a0 > ? find_held_lock+0x2d/0x110 > ? __pfx_btrfs_ioctl+0x10/0x10 > ? lock_release+0x20e/0x710 > ? do_sigaction+0x3f0/0x860 > ? __pfx_do_vfs_ioctl+0x10/0x10 > ? do_raw_spin_lock+0x11e/0x240 > ? lockdep_hardirqs_on_prepare+0x270/0x3e0 > ? _raw_spin_unlock_irq+0x28/0x50 > ? do_sigaction+0x3f0/0x860 > ? __pfx_do_sigaction+0x10/0x10 > ? __x64_sys_rt_sigaction+0x18e/0x1e0 > ? __pfx___x64_sys_rt_sigaction+0x10/0x10 > ? __x64_sys_close+0x7c/0xd0 > __x64_sys_ioctl+0x137/0x190 > do_syscall_64+0x71/0x140 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > RIP: 0033:0x7f0bd1114f9b > Code: Unable to access opcode bytes at 0x7f0bd1114f71. > RSP: 002b:00007ffc8a8c3130 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f0bd1114f9b > RDX: 00007ffc8a8c35e0 RSI: 00000000ca289435 RDI: 0000000000000003 > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000007 > R10: 0000000000000008 R11: 0000000000000246 R12: 00007ffc8a8c6c85 > R13: 00000000398e72a0 R14: 0000000000004361 R15: 0000000000000004 > </TASK> > > This happens because on RAID stripe-tree filesystems we recurse back into > btrfs_map_block() on scrub to perform the logical to device physical > mapping. > > But as the device replace task is already holding the dev_replace::rwsem > we deadlock. > > So don't take the dev_replace::rwsem in case our task is the task performing > the device replace. > > Suggested-by: Filipe Manana <fdmanana@suse.com> > Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Filipe Manana <fdmanana@suse.com> Looks good, thanks. The review applies regardless of using task_struct or pid_t. > --- > fs/btrfs/dev-replace.c | 2 ++ > fs/btrfs/fs.h | 2 ++ > fs/btrfs/volumes.c | 8 +++++--- > 3 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c > index 83d5cdd77f29..604399e59a3d 100644 > --- a/fs/btrfs/dev-replace.c > +++ b/fs/btrfs/dev-replace.c > @@ -641,6 +641,7 @@ static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info, > return ret; > > down_write(&dev_replace->rwsem); > + dev_replace->replace_task = current; > switch (dev_replace->replace_state) { > case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED: > case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED: > @@ -994,6 +995,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, > list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list); > fs_devices->rw_devices++; > > + dev_replace->replace_task = NULL; > up_write(&dev_replace->rwsem); > btrfs_rm_dev_replace_blocked(fs_info); > > diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h > index 79f64e383edd..cbfb225858a5 100644 > --- a/fs/btrfs/fs.h > +++ b/fs/btrfs/fs.h > @@ -317,6 +317,8 @@ struct btrfs_dev_replace { > > struct percpu_counter bio_counter; > wait_queue_head_t replace_wait; > + > + struct task_struct *replace_task; > }; > > /* > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 8f340ad1d938..995b0647f538 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -6480,13 +6480,15 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, > max_len = btrfs_max_io_len(map, map_offset, &io_geom); > *length = min_t(u64, map->chunk_len - map_offset, max_len); > > - down_read(&dev_replace->rwsem); > + if (dev_replace->replace_task != current) > + down_read(&dev_replace->rwsem); > + > dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace); > /* > * Hold the semaphore for read during the whole operation, write is > * requested at commit time but must wait. > */ > - if (!dev_replace_is_ongoing) > + if (!dev_replace_is_ongoing && dev_replace->replace_task != current) > up_read(&dev_replace->rwsem); > > switch (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) { > @@ -6626,7 +6628,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, > bioc->mirror_num = io_geom.mirror_num; > > out: > - if (dev_replace_is_ongoing) { > + if (dev_replace_is_ongoing && dev_replace->replace_task != current) { > lockdep_assert_held(&dev_replace->rwsem); > /* Unlock and let waiting writers proceed */ > up_read(&dev_replace->rwsem); > -- > 2.43.0 > >
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 83d5cdd77f29..604399e59a3d 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -641,6 +641,7 @@ static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info, return ret; down_write(&dev_replace->rwsem); + dev_replace->replace_task = current; switch (dev_replace->replace_state) { case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED: case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED: @@ -994,6 +995,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list); fs_devices->rw_devices++; + dev_replace->replace_task = NULL; up_write(&dev_replace->rwsem); btrfs_rm_dev_replace_blocked(fs_info); diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h index 79f64e383edd..cbfb225858a5 100644 --- a/fs/btrfs/fs.h +++ b/fs/btrfs/fs.h @@ -317,6 +317,8 @@ struct btrfs_dev_replace { struct percpu_counter bio_counter; wait_queue_head_t replace_wait; + + struct task_struct *replace_task; }; /* diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 8f340ad1d938..995b0647f538 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -6480,13 +6480,15 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, max_len = btrfs_max_io_len(map, map_offset, &io_geom); *length = min_t(u64, map->chunk_len - map_offset, max_len); - down_read(&dev_replace->rwsem); + if (dev_replace->replace_task != current) + down_read(&dev_replace->rwsem); + dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace); /* * Hold the semaphore for read during the whole operation, write is * requested at commit time but must wait. */ - if (!dev_replace_is_ongoing) + if (!dev_replace_is_ongoing && dev_replace->replace_task != current) up_read(&dev_replace->rwsem); switch (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) { @@ -6626,7 +6628,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, bioc->mirror_num = io_geom.mirror_num; out: - if (dev_replace_is_ongoing) { + if (dev_replace_is_ongoing && dev_replace->replace_task != current) { lockdep_assert_held(&dev_replace->rwsem); /* Unlock and let waiting writers proceed */ up_read(&dev_replace->rwsem);