We allow recursive mounts with subvol options such as [1]
[1]
mount -o rw,compress=lzo /dev/sdc /btrfs1
mount -o ro,subvol=sv2 /dev/sdc /btrfs2
And except for the btrfs-specific subvol and subvolid options
all-other options are just ignored in the subsequent mounts.
In the below example [2] the effect compression is only zlib,
even though there was no error for the option -o compress=lzo.
[2]
----
# mount -o compress=zlib /dev/sdc /btrfs1
#echo $?
0
# mount -o compress=lzo /dev/sdc /btrfs
#echo $?
0
#cat /proc/self/mounts
::
/dev/sdc /btrfs1 btrfs
rw,relatime,compress=zlib,space_cache,subvolid=5,subvol=/ 0 0
/dev/sdc /btrfs btrfs
rw,relatime,compress=zlib,space_cache,subvolid=5,subvol=/ 0 0
----
Further, random string .. has no error as well.
-----
# mount -o compress=zlib /dev/sdc /btrfs1
#echo $?
0
# mount -o something /dev/sdc /btrfs
#echo $?
0
-----
This patch fixes the above issue, by checking the if the passed
options are only subvol or subvolid in the subsequent mount.
Signed-off-by: Anand Jain <anand.j...@oracle.com>
---
fs/btrfs/super.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 9530a333d302..e0e542345c38 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -389,6 +389,44 @@ static const match_table_t tokens = {
{Opt_err, NULL},
};
+static int parse_recursive_mount_options(char *data)
+{
+ substring_t args[MAX_OPT_ARGS];
+ char *options, *orig;
+ char *p;
+ int ret = 0;
+
+ /*
+ * This is not a remount thread, but we allow recursive mounts
+ * with varying RO/RW flag to support subvol-mounts. So error-out
+ * if any other option being passed in here.
+ */
+
+ options = kstrdup(data, GFP_NOFS);
+ if (!options)
+ return -ENOMEM;
+
+ orig = options;
+
+ while ((p = strsep(&options, ",")) != NULL) {
+ int token;
+ if (!*p)
+ continue;
+
+ token = match_token(p, tokens, args);
+ switch(token) {
+ case Opt_subvol:
+ case Opt_subvolid:
+ break;
+ default:
+ ret = -EBUSY;
+ }
+ }
+
+ kfree(orig);
+ return ret;
+}
+
/*
* Regular mount options parser. Everything that is needed only when
* reading in a new superblock is parsed here.
@@ -1611,6 +1649,8 @@ static struct dentry *btrfs_mount(struct file_system_type
*fs_type, int flags,
free_fs_info(fs_info);
if ((flags ^ s->s_flags) & MS_RDONLY)
error = -EBUSY;
+ if (parse_recursive_mount_options(data))
+ error = -EBUSY;
} else {
snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
btrfs_sb(s)->bdev_holder = fs_type;
--
2.10.0
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