Re: [PATCH 4/7] btrfs-progs: Allow parse_qgroupid() to resolve subvolume path into qgroupid.

[Qu Wenruo]

-------- Original Message  --------
Subject: Re: [PATCH 4/7] btrfs-progs: Allow parse_qgroupid() to resolve 
subvolume path into qgroupid.
From: Wang Shilong <wangshilong1...@gmail.com>
To: Qu Wenruo <quwen...@cn.fujitsu.com>
Date: 2015年02月27日 16:41



Now parse_qgroupid() can resolve subvolume path into qgroupid.
This is quite handy for handling level 0 qgroupid, and user don't need
to resolve rootid by hand now.

oh, not sure if this is safe, for example, if user do something like:

# btrfs sub create 258(subvolume id = 300)

if 258 is passing, so it will be treated as subvolume id?
Immediate number has higher privilege than path, so 258 is first 
considered as a subvolid and path will not be resolved, just as the old 
days.

If user really want to do things like that, passing "./258" will be the 
best method.

Thanks,
Qu



Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
utils.c | 46 ++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 42 insertions(+), 4 deletions(-)

diff --git a/utils.c b/utils.c
index fc2791b..509c5ec 100644
--- a/utils.c
+++ b/utils.c
@@ -1708,6 +1708,25 @@ scan_again:
}

/*
+ * Unsafe subvolume check.
+ *
+ * This only checks ino == BTRFS_FIRST_FREE_OBJECTID, even it is not in a
+ * btrfs mount point.
+ * Must use together with other reliable method like btrfs ioctl.
+ */
+static int __is_subvol(char *path)
+{
+       struct stat st;
+       int ret;
+
+       ret = lstat(path, &st);
+       if (ret < 0)
+               return ret;
+
+       return st.st_ino == BTRFS_FIRST_FREE_OBJECTID;
+}
+
+/*
  * A not-so-good version fls64. No fascinating optimization since
  * no one except parse_size use it
  */
@@ -1802,24 +1821,43 @@ u64 parse_qgroupid(char *p)
        char *ptr_parse_end = NULL;
        u64 level;
        u64 id;
+       int fd;
+       int ret = 0;

+       if (p[0] == '/')
+               goto path;
+
+       /* Numeric format like '0/257' is the primary case */
        if (!s) {
                id = strtoull(p, &ptr_parse_end, 10);
                if (ptr_parse_end != ptr_src_end)
-                       goto err;
+                       goto path;
                return id;
        }
        level = strtoull(p, &ptr_parse_end, 10);
        if (ptr_parse_end != s)
-               goto err;
+               goto path;

        id = strtoull(s+1, &ptr_parse_end, 10);
        if (ptr_parse_end != ptr_src_end)
-               goto  err;
+               goto path;

        return (level << BTRFS_QGROUP_LEVEL_SHIFT) | id;
+path:
+       /* Path format like subv at 'my_subvol' is the fallback case */
+       ret = __is_subvol(p);
+       if (ret < 0 || !ret)
+               goto err;
+       fd = open(p, O_RDONLY);
+       if (fd < 0)
+               goto err;
+       ret = lookup_ino_rootid(fd, &id);
+       close(fd);
+       if (ret < 0)
+               goto err;
+       return id;
err:
-       fprintf(stderr, "ERROR:invalid qgroupid\n");
+       fprintf(stderr, "ERROR:invalid qgroupid or subvolume path\n");
        exit(-1);
}

--
2.3.0

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Best Regards,
Wang Shilong

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