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btrfs: scrub: move scrub_setup_ctx allocation out of device_list_mutex 

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>
This commit is contained in:
David Sterba 2018-12-04 16:11:56 +01:00
parent 92f7ba434f
commit 0e94c4f45d
1 changed files with 18 additions and 12 deletions
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30
fs/btrfs/scrub.c
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@ -3835,13 +3835,18 @@ 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 &&
@ -3849,7 +3854,8 @@ 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);
@ -3857,7 +3863,8 @@ 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;
}
down_read(&fs_info->dev_replace.rwsem);
@ -3867,7 +3874,8 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
up_read(&fs_info->dev_replace.rwsem);
mutex_unlock(&fs_info->scrub_lock);
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
return -EINPROGRESS;
ret = -EINPROGRESS;
goto out_free_ctx;
}
up_read(&fs_info->dev_replace.rwsem);
@ -3875,16 +3883,9 @@ 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);
@ -3937,6 +3938,11 @@ 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;
}