On 06/21/2018 01:51 AM, David Sterba wrote:
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.
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx>
Thanks, Anand
---
fs/btrfs/super.c | 12 +++++++++++-
fs/btrfs/volumes.c | 4 ++--
2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 81107ad49f3a..735402ed3154 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -917,8 +917,10 @@ 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;
@@ -1539,7 +1541,9 @@ 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;
@@ -2234,15 +2238,21 @@ 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);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 02246f9af0a3..958bfe1a725c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1226,6 +1226,8 @@ 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.
@@ -1244,13 +1246,11 @@ 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);
if (IS_ERR(device))
ret = PTR_ERR(device);
else
*fs_devices_ret = device->fs_devices;
- mutex_unlock(&uuid_mutex);
btrfs_release_disk_super(page);
--
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