-------- Original Message --------
Subject: [PATCH 3/3] Btrfs: show subvol= and subvolid= in /proc/mounts
From: Omar Sandoval <osan...@osandov.com>
To: Chris Mason <c...@fb.com>, Josef Bacik <jba...@fb.com>, David Sterba
<dste...@suse.cz>, <linux-bt...@vger.kernel.org>
Date: 2015年04月08日 13:34
Currently, userspace has no way to know which subvolume is mounted.But,
now that we're guaranteed to have a meaningful root dentry, we can just
export and use seq_dentry() in btrfs_show_options(). The subvolume ID is
easy to get, so put that in there, too.
Oh, I sent patch like this long long ago but still not merged.
http://comments.gmane.org/gmane.comp.file-systems.btrfs/36997
My patch doesn't do it in mount options, but add it to /proc/self/mountinfo.
In fact, if you mount subvolume with "-o subvol=", then
/proc/self/mountinfo should has the result like below:
73 33 0:35 / /mnt/test rw,relatime shared:57 - btrfs /dev/sdb rw,space_cache
75 33 0:35 /test /mnt/scratch rw,relatime shared:59 - btrfs /dev/sdb
rw,space_cache
The only problem is, if you mount with "-o subvolid=" as the *FIRST*
mount of the fs, then mountinfo can't show it.
My patch will fix the above problem but not merged yet...
Thanks,
Qu
Signed-off-by: Omar Sandoval <osan...@osandov.com>
---
fs/btrfs/super.c | 4 ++++
fs/seq_file.c | 1 +
2 files changed, 5 insertions(+)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 5ab9801..5e14bb6 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1193,6 +1193,10 @@ static int btrfs_show_options(struct seq_file *seq,
struct dentry *dentry)
seq_puts(seq, ",fatal_errors=panic");
if (info->commit_interval != BTRFS_DEFAULT_COMMIT_INTERVAL)
seq_printf(seq, ",commit=%d", info->commit_interval);
+ seq_puts(seq, ",subvol=");
+ seq_dentry(seq, dentry, " \t\n\\");
+ seq_printf(seq, ",subvolid=%llu",
+ BTRFS_I(d_inode(dentry))->root->root_key.objectid);
return 0;
}
diff --git a/fs/seq_file.c b/fs/seq_file.c
index 555f821..52b4927 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -538,6 +538,7 @@ int seq_dentry(struct seq_file *m, struct dentry *dentry,
const char *esc)
return res;
}
+EXPORT_SYMBOL(seq_dentry);
static void *single_start(struct seq_file *p, loff_t *pos)
{
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