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btrfs: lift uuid_mutex to callers of btrfs_scan_one_device

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Prepartory work to fix race between mount and device scan.

The callers will have to manage the critical section, eg. mount wants to
scan and then call btrfs_open_devices without the ioctl scan walking in
and modifying the fs devices in the meantime.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2018-06-19 16:37:36 +02:00
parent 7bcb8164ad
commit 899f9307c3
2 changed files with 13 additions and 3 deletions
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12
fs/btrfs/super.c
View file

@ -915,8 +915,10 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
error = -ENOMEM;
goto out;
}
mutex_lock(&uuid_mutex);
error = btrfs_scan_one_device(device_name,
flags, holder, fs_devices);
mutex_unlock(&uuid_mutex);
kfree(device_name);
if (error)
goto out;
@ -1537,7 +1539,9 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
return ERR_PTR(error);
}
mutex_lock(&uuid_mutex);
error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
mutex_unlock(&uuid_mutex);
if (error)
goto error_sec_opts;
@ -2232,15 +2236,21 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
switch (cmd) {
case BTRFS_IOC_SCAN_DEV:
mutex_lock(&uuid_mutex);
ret = btrfs_scan_one_device(vol->name, FMODE_READ,
&btrfs_root_fs_type, &fs_devices);
mutex_unlock(&uuid_mutex);
break;
case BTRFS_IOC_DEVICES_READY:
mutex_lock(&uuid_mutex);
ret = btrfs_scan_one_device(vol->name, FMODE_READ,
&btrfs_root_fs_type, &fs_devices);
if (ret)
if (ret) {
mutex_unlock(&uuid_mutex);
break;
}
ret = !(fs_devices->num_devices == fs_devices->total_devices);
mutex_unlock(&uuid_mutex);
break;
case BTRFS_IOC_GET_SUPPORTED_FEATURES:
ret = btrfs_ioctl_get_supported_features((void __user*)arg);

4
fs/btrfs/volumes.c
View file

@ -1224,6 +1224,8 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
int ret = 0;
u64 bytenr;
lockdep_assert_held(&uuid_mutex);
/*
* we would like to check all the supers, but that would make
* a btrfs mount succeed after a mkfs from a different FS.
@ -1242,7 +1244,6 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
goto error_bdev_put;
}
mutex_lock(&uuid_mutex);
device = device_list_add(path, disk_super, &new_device_added);
if (IS_ERR(device)) {
ret = PTR_ERR(device);
@ -1251,7 +1252,6 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
if (new_device_added)
btrfs_free_stale_devices(path, device);
}
mutex_unlock(&uuid_mutex);
btrfs_release_disk_super(page);