Re: mkstemp fails on cifs linux-2.6.31-rc1 / samba-3.3.6

On Tue, Jun 30, 2009 at 8:40 AM, Jeff Layton<[email protected]> wrote:
> On Tue, 2009-06-30 at 08:27 -0500, Shirish Pargaonkar wrote:
>> On Tue, Jun 30, 2009 at 8:01 AM, Jeff Layton<[email protected]> wrote:
>> > On Tue, 2009-06-30 at 13:00 +0200, Wilhelm Meier wrote:
>> >> Hi,
>> >>
>> >> I made a simple test with cifs in linux-2.6.31-rc1 to see if the so called
>> >> kmail-problem (cifs-user-homes are totally unusable for kmail-mail-cache)
>> >> still remains. Than I ran into a strange problem using "sed -i <command> <file-
>> >> on-cifs>". "sed" uses mkstemp libc-funktion and fails with EEXIST, writing
>> >> therefore tons of files onto the cifs-share.
>> >>
>> >> You can reproduce it with:
>> >>
>> >> strace mktemp -p . abcXXXXXX 2>&1 | more
>> >>
>> >> giving
>> >>
>> >> stat64(".", {st_mode=S_IFDIR|0700, st_size=0, ...}) = 0
>> >> open("./abcUJcKWM", O_RDWR|O_CREAT|O_EXCL, 0600) = -1 EEXIST (File exists)
>> >> stat64(".", {st_mode=S_IFDIR|0700, st_size=0, ...}) = 0
>> >> open("./abcUGJaiA", O_RDWR|O_CREAT|O_EXCL, 0600) = -1 EEXIST (File exists)
>> >> stat64(".", {st_mode=S_IFDIR|0700, st_size=0, ...}) = 0
>> >> open("./abcWfKacs", O_RDWR|O_CREAT|O_EXCL, 0600) = -1 EEXIST (File exists)
>> >> stat64(".", {st_mode=S_IFDIR|0700, st_size=0, ...}) = 0
>> >> open("./abcBaGjWM", O_RDWR|O_CREAT|O_EXCL, 0600) = -1 EEXIST (File exists)
>> >>
>> >> This is the same on 2.6.31-rc1-git6.
>> >>
>> >> This is not the case in 2.6.26-2-vserver-686 (debian).
>> >>
>> >> The Samba-Server is lenny with samba-enterprise:
>> >> kmux-fs:/# dpkg -l | grep samba
>> >> ii  sernet-samba                    3.3.6-24                 a LanManager-like
>> >> file and printer server fo
>> >> ii  sernet-samba-common             3.3.6-24                 Samba common files
>> >> used by both the server a
>> >> ii  sernet-samba-keyring            1.1                      GnuPG archive
>> >> keys of the SerNet Samba archi
>> >>
>> >> If I change Samba to the lenny-version
>> >>
>> >> ii  samba                           2:3.2.5-4lenny6          a LanManager-like
>> >> file and printer server fo
>> >> ii  samba-common                    2:3.2.5-4lenny6          Samba common files
>> >> used by both the server a
>> >>
>> >> the described test-case is fine.
>> >>
>> >>
>> >
>> > I can reproduce this too.
>> >
>> > Looks like another regression from the create-on-lookup patches. I
>> > commented the relevant chunk out of cifs_lookup and that fixes the
>> > issue.
>> >
>> > Shirish, thoughts?
>> >
>> > --
>> > Jeff Layton <[email protected]>
>> >
>> >
>>
>> Jeff, Wilhelm,
>>
>> I will spend some time later in the day on this but one thought came to mind,
>> Jeff, we took out a line where if there was exclusive create, we would let
>> vfs handle it, not sure if putting it back would help!
>>
>
> Probably...it does seem to be related to O_EXCL. Rather than just
> blindly putting that back though, I'd like to see some understanding
> about why this is failing, and a consistent idea about how this is code
> is intended to work.
>
> Skipping create on lookup for the O_EXCL case seems ass-backwards to me.
> Doing it on lookup should help atomicity, and that's just what you want
> for O_EXCL.
>
> --
> Jeff Layton <[email protected]>
>
>

So adding this back helps, this is what I had initially.  The reason I
did put this was because I
was not sure how to handle exclusive create then when I added lookup
intent code to cifs.
It sounds correct that a Samba server would handle the case of
exclusive create for cifs
and return an appropriate code (EEXISTS) in the response, may be cifs
is not handling it.

This is what I get with this patch in

# mktemp -p . abcXXXXXX
./abcWpeApL

I am debugging further to identify what the exact problem is.


diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 7dc6b74..d6f9ecd 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -673,6 +673,8 @@ cifs_lookup(struct inode *parent_dir_inode, struct
dentry *direntry,
                if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY)) &&
                     (nd->flags & LOOKUP_OPEN) && !pTcon->broken_posix_open &&
                     (nd->intent.open.flags & O_CREAT)) {
+                       if (!((nd->intent.open.flags & O_CREAT) &&
+                               (nd->intent.open.flags & O_EXCL))) {
                        rc = cifs_posix_open(full_path, &newInode,
                                        parent_dir_inode->i_sb,
                                        nd->intent.open.create_mode,
@@ -689,6 +691,7 @@ cifs_lookup(struct inode *parent_dir_inode, struct
dentry *direntry,
                                posix_open = true;
                        else if ((rc == -EINVAL) || (rc != -EOPNOTSUPP))
                                pTcon->broken_posix_open = true;
+                       }
                }
                if (!posix_open)
                        rc = cifs_get_inode_info_unix(&newInode, full_path,