Re: [PATCH] Trim extra slash in v4 nfs_path

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Hi Anna,

On 20 Jun 2016, at 11:38, Benjamin Coddington wrote:

On 20 Jun 2016, at 11:08, Anna Schumaker wrote:

Hi Ben,

On 06/15/2016 03:02 PM, Benjamin Coddington wrote:
A NFSv4 mount of a subdirectory will show an extra slash (as in
'server://path') in proc's mountinfo which will not match the device name and path. This can cause problems for programs searching for the mount. Fix this by checking for a leading slash in the dentry path, if so trim
away any trailing slashes in the device name.

Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
---
 fs/nfs/namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index c8162c660c44..5551e8ef67fd 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -98,7 +98,7 @@ rename_retry:
 		return end;
 	}
 	namelen = strlen(base);
-	if (flags & NFS_PATH_CANONICAL) {
+	if (*end == '/') {

Are we getting here through nfs_show_devname()? Because it looks like that function is passing 0 for flags instead of NFS_PATH_CANONICAL.

We can get here with or withount NFS_PATH_CANONICAL, through
nfs_show_devname() or nfs4_path() or nfs_do_submount().


Earlier in this function we have a check for:
    if ((flags & NFS_PATH_CANONICAL) && *end != '/')

Should we be checking if NFS_PATH_CANONICAL is set here, too?

I don't think we need it.

The "if (flags & NFS_PATH_CANONICAL) {" was meant to cover the case where NFS_PATH_CANONICAL had earlier added a leading '/' to the path, and so would trim away any trailing '/' from the base. So, don't combine server:/ and
/path into server://path after adding a leading '/' to the path.

The logic here is simplified such that we should _never_ concat these two:
a base:/ and a /path, otherwise we'll have server://path.

Further confusing the matter is that for v3 mounts, the base is server:/path
and the path is '/' (which is added by NFS_PATH_CANONICAL), but for v4
mounts the base is server:/ and the path is /path/to/export

Did this make any sense, or should I try to make it clearer or rework this?

This patch seems like just a minor fix, but the double slashes breaks some mount parsing in tests we have.

Ben
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