28.04.2017 12:14, Anand Jain пишет: > 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;
But if subvol= was passed, it should not reach this place at all - btrfs_mount() returns earlier in if (subvol_name || subvol_objectid != BTRFS_FS_TREE_OBJECTID) { /* mount_subvol() will free subvol_name. */ return mount_subvol(subvol_name, subvol_objectid, flags, device_name, data); } So check for subvol here seems redundant. > } else { > snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev); > btrfs_sb(s)->bdev_holder = fs_type; > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html