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Subject[PATCH 4.18 148/197] btrfs: lift uuid_mutex to callers of btrfs_scan_one_device
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Sterba <dsterba@suse.com>

[ Upstream commit 899f9307c33ce4758c30a076b10ed54d5c91c6e7 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/super.c | 12 +++++++++++-
fs/btrfs/volumes.c | 4 ++--
2 files changed, 13 insertions(+), 3 deletions(-)

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -917,8 +917,10 @@ static int btrfs_parse_early_options(con
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(s
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;

@@ -2236,15 +2240,21 @@ static long btrfs_control_ioctl(struct f

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);
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1241,6 +1241,8 @@ int btrfs_scan_one_device(const char *pa
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.
@@ -1259,7 +1261,6 @@ int btrfs_scan_one_device(const char *pa
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);
@@ -1268,7 +1269,6 @@ int btrfs_scan_one_device(const char *pa
if (new_device_added)
btrfs_free_stale_devices(path, device);
}
- mutex_unlock(&uuid_mutex);

btrfs_release_disk_super(page);


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