linux-kernel - Re: Fix lookup so we don't try to open, just create

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Date:	Sat, 23 May 2009 10:56:44 -0500
From:	Steve French <smfrench@...il.com>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	Shirish Pargaonkar <shirishpargaonkar@...il.com>,
	Jeremy Allison <jra@...ba.org>,
	"linux-cifs-client@...ts.samba.org" 
	<linux-cifs-client@...ts.samba.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Fix lookup so we don't try to open, just create

On Sat, May 23, 2009 at 3:43 AM, Jeff Layton <jlayton@...hat.com> wrote:
> It's also preferable not to break up an if block like that. That is, the
> comment should be moved up outside of the if block and to the left.
>
> --
> Jeff Layton <jlayton@...hat.com>

OK - simplified per Jeff's suggestions, and also simplified the error
check so it falls through to old unix query path on everything but rc
== 0 or rc == -ENOENT  (which avoids having to worry about future
EISDIR vs. EACCES anyway).  Will begin testing, but with a change this
small, looks lower risk to not map the errors (per Jeff's suggestion).
 Most of the change size is reformatting the comments and the one
level of now superfluous indentation.

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index f49d684..3758965 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -657,31 +657,36 @@ cifs_lookup(struct inode *parent_dir_inode,
struct dentry *direntry,
 	}
 	cFYI(1, ("Full path: %s inode = 0x%p", full_path, direntry->d_inode));

+	/* Posix open is only called (at lookup time) for file create now.
+	 * For opens (rather than creates), because we do not know if it
+	 * is a file or directory yet, and current Samba no longer allows
+	 * us to do posix open on dirs, we could end up wasting an open call
+	 * on what turns out to be a dir. For file opens, we wait to call posix
+	 * open till cifs_open.  It could be added here (lookup) in the future
+	 * but the performance tradeoff of the extra network request when EISDIR
+	 * or EACCES is returned would have to be weighed against the 50%
+	 * reduction in network traffic in the other paths.
+	 */
 	if (pTcon->unix_ext) {
 		if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY)) &&
-		     (nd->flags & LOOKUP_OPEN) && !pTcon->broken_posix_open) {
-			if (!((nd->intent.open.flags & O_CREAT) &&
-					(nd->intent.open.flags & O_EXCL))) {
-				rc = cifs_posix_open(full_path, &newInode,
+		     (nd->flags & LOOKUP_OPEN) && !pTcon->broken_posix_open &&
+		     (nd->intent.open.flags & O_CREAT)) {
+			rc = cifs_posix_open(full_path, &newInode,
 					parent_dir_inode->i_sb,
 					nd->intent.open.create_mode,
 					nd->intent.open.flags, &oplock,
 					&fileHandle, xid);
-				/*
-				 * This code works around a bug in
-				 * samba posix open in samba versions 3.3.1
-				 * and earlier where create works
-				 * but open fails with invalid parameter.
-				 * If either of these error codes are
-				 * returned, follow the normal lookup.
-				 * Otherwise, the error during posix open
-				 * is handled.
-				 */
-				if ((rc != -EINVAL) && (rc != -EOPNOTSUPP))
-					posix_open = true;
-				else
-					pTcon->broken_posix_open = true;
-			}
+			/*
+			 * The check below works around a bug in POSIX
+			 * open in samba versions 3.3.1 and earlier where
+			 * open could incorrectly fail with invalid parameter.
+			 * If either that or op not supported returned, follow
+			 * the normal lookup.
+			 */
+			if ((rc == 0) || (rc == -ENOENT))
+				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,



See attached:




-- 
Thanks,

Steve

View attachment "posix-open-only-on-create-and-fix-isdir-error-mapping-ver2.patch" of type "text/x-diff" (2458 bytes)