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Subject[PATCH AUTOSEL 4.19 078/167] btrfs: scrub: move scrub_setup_ctx allocation out of device_list_mutex
Date
From: David Sterba <dsterba@suse.com>

[ Upstream commit 0e94c4f45d14cf89d1f40c91b0a8517e791672a7 ]

The scrub context is allocated with GFP_KERNEL and called from
btrfs_scrub_dev under the fs_info::device_list_mutex. This is not safe
regarding reclaim that could try to flush filesystem data in order to
get the memory. And the device_list_mutex is held during superblock
commit, so this would cause a lockup.

Move the alocation and initialization before any changes that require
the mutex.

Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/scrub.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index efaad3e1b295a..56c4d2236484f 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -3837,13 +3837,18 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
return -EINVAL;
}

+ /* Allocate outside of device_list_mutex */
+ sctx = scrub_setup_ctx(fs_info, is_dev_replace);
+ if (IS_ERR(sctx))
+ return PTR_ERR(sctx);

mutex_lock(&fs_info->fs_devices->device_list_mutex);
dev = btrfs_find_device(fs_info, devid, NULL, NULL);
if (!dev || (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) &&
!is_dev_replace)) {
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
- return -ENODEV;
+ ret = -ENODEV;
+ goto out_free_ctx;
}

if (!is_dev_replace && !readonly &&
@@ -3851,7 +3856,8 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
btrfs_err_in_rcu(fs_info, "scrub: device %s is not writable",
rcu_str_deref(dev->name));
- return -EROFS;
+ ret = -EROFS;
+ goto out_free_ctx;
}

mutex_lock(&fs_info->scrub_lock);
@@ -3859,7 +3865,8 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &dev->dev_state)) {
mutex_unlock(&fs_info->scrub_lock);
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
- return -EIO;
+ ret = -EIO;
+ goto out_free_ctx;
}

btrfs_dev_replace_read_lock(&fs_info->dev_replace);
@@ -3869,7 +3876,8 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
mutex_unlock(&fs_info->scrub_lock);
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
- return -EINPROGRESS;
+ ret = -EINPROGRESS;
+ goto out_free_ctx;
}
btrfs_dev_replace_read_unlock(&fs_info->dev_replace);

@@ -3877,16 +3885,9 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
if (ret) {
mutex_unlock(&fs_info->scrub_lock);
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
- return ret;
+ goto out_free_ctx;
}

- sctx = scrub_setup_ctx(fs_info, is_dev_replace);
- if (IS_ERR(sctx)) {
- mutex_unlock(&fs_info->scrub_lock);
- mutex_unlock(&fs_info->fs_devices->device_list_mutex);
- scrub_workers_put(fs_info);
- return PTR_ERR(sctx);
- }
sctx->readonly = readonly;
dev->scrub_ctx = sctx;
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
@@ -3939,6 +3940,11 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,

scrub_put_ctx(sctx);

+ return ret;
+
+out_free_ctx:
+ scrub_free_ctx(sctx);
+
return ret;
}

--
2.20.1
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