[PATCH] autofs4 needs to force fail return revalidate

For a long time now I have had a problem with not being able to return a lookup failure on an existsing directory. In autofs this corresponds to a mount failure on a autofs managed mount entry that is browsable (and so the mount point directory exists). While this problem has been present for a long time I've avoided resolving it because it was not very visible. But now that autofs v5 has "mount and expire on demand" of nested multiple mounts, such as is found when mounting an export list from a server, solving the problem cannot be avoided any longer. I've tried very hard to find a way to do this entirely within the autofs4 module but have not been able to find a satisfactory way to achieve it. So, I need to propose a change to the VFS. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] autofs4 needs to force fail return revalidate
For a long time now I have had a problem with not being able to return a lookup failure on an existsing directory. In autofs this corresponds to a mount failure on a autofs managed mount entry that is browsable (and so the mount point directory exists). While this problem has been present for a long time I've avoided resolving it because it was not very visible. But now that autofs v5 has "mount and expire on demand" of nested multiple mounts, such as is found when mounting an export list from a server, solving the problem cannot be avoided any longer. I've tried very hard to find a way to do this entirely within the autofs4 module but have not been able to find a satisfactory way to achieve it. So, I need to propose a change to the VFS. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Ian Kent · Linus Torvalds
1 parent 1183dc943c
Showing 2 changed files with 65 additions and 23 deletions Side-by-side Diff
fs/autofs4/root.c
fs/namei.c
@@ -137,7 +137,9 @@
 		nd.flags = LOOKUP_DIRECTORY;
 		ret = (dentry->d_op->d_revalidate)(dentry, &nd);
  
-		if (!ret) {
+		if (ret <= 0) {
+			if (ret < 0)
+				status = ret;
 			dcache_dir_close(inode, file);
 			goto out;
 		}
  
@@ -400,13 +402,23 @@
 	struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 	int oz_mode = autofs4_oz_mode(sbi);
 	int flags = nd ? nd->flags : 0;
-	int status = 0;
+	int status = 1;
  
 	/* Pending dentry */
 	if (autofs4_ispending(dentry)) {
-		if (!oz_mode)
-			status = try_to_fill_dentry(dentry, flags);
-		return !status;
+		/* The daemon never causes a mount to trigger */
+		if (oz_mode)
+			return 1;
+
+		/*
+		 * A zero status is success otherwise we have a
+		 * negative error code.
+		 */
+		status = try_to_fill_dentry(dentry, flags);
+		if (status == 0)
+				return 1;
+
+		return status;
 	}
  
 	/* Negative dentry.. invalidate if "old" */
@@ -421,9 +433,19 @@
 		DPRINTK("dentry=%p %.*s, emptydir",
 			 dentry, dentry->d_name.len, dentry->d_name.name);
 		spin_unlock(&dcache_lock);
-		if (!oz_mode)
-			status = try_to_fill_dentry(dentry, flags);
-		return !status;
+		/* The daemon never causes a mount to trigger */
+		if (oz_mode)
+			return 1;
+
+		/*
+		 * A zero status is success otherwise we have a
+		 * negative error code.
+		 */
+		status = try_to_fill_dentry(dentry, flags);
+		if (status == 0)
+			return 1;
+
+		return status;
 	}
 	spin_unlock(&dcache_lock);
  
@@ -372,6 +372,30 @@
 		fput(nd->intent.open.file);
 }
  
+static inline struct dentry *
+do_revalidate(struct dentry *dentry, struct nameidata *nd)
+{
+	int status = dentry->d_op->d_revalidate(dentry, nd);
+	if (unlikely(status <= 0)) {
+		/*
+		 * The dentry failed validation.
+		 * If d_revalidate returned 0 attempt to invalidate
+		 * the dentry otherwise d_revalidate is asking us
+		 * to return a fail status.
+		 */
+		if (!status) {
+			if (!d_invalidate(dentry)) {
+				dput(dentry);
+				dentry = NULL;
+			}
+		} else {
+			dput(dentry);
+			dentry = ERR_PTR(status);
+		}
+	}
+	return dentry;
+}
+
 /*
  * Internal lookup() using the new generic dcache.
  * SMP-safe
@@ -386,12 +410,9 @@
 	if (!dentry)
 		dentry = d_lookup(parent, name);
  
-	if (dentry && dentry->d_op && dentry->d_op->d_revalidate) {
-		if (!dentry->d_op->d_revalidate(dentry, nd) && !d_invalidate(dentry)) {
-			dput(dentry);
-			dentry = NULL;
-		}
-	}
+	if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
+		dentry = do_revalidate(dentry, nd);
+
 	return dentry;
 }
  
  
@@ -484,10 +505,9 @@
 	 */
 	mutex_unlock(&dir->i_mutex);
 	if (result->d_op && result->d_op->d_revalidate) {
-		if (!result->d_op->d_revalidate(result, nd) && !d_invalidate(result)) {
-			dput(result);
+		result = do_revalidate(result, nd);
+		if (!result)
 			result = ERR_PTR(-ENOENT);
-		}
 	}
 	return result;
 }
@@ -767,12 +787,12 @@
 	goto done;
  
 need_revalidate:
-	if (dentry->d_op->d_revalidate(dentry, nd))
-		goto done;
-	if (d_invalidate(dentry))
-		goto done;
-	dput(dentry);
-	goto need_lookup;
+	dentry = do_revalidate(dentry, nd);
+	if (!dentry)
+		goto need_lookup;
+	if (IS_ERR(dentry))
+		goto fail;
+	goto done;
  
 fail:
 	return PTR_ERR(dentry);
...	...	@@ -137,7 +137,9 @@
137	137	nd.flags = LOOKUP_DIRECTORY;
138	138	ret = (dentry->d_op->d_revalidate)(dentry, &nd);
139	139
140		- if (!ret) {
	140	+ if (ret <= 0) {
	141	+ if (ret < 0)
	142	+ status = ret;
141	143	dcache_dir_close(inode, file);
142	144	goto out;
143	145	}
144	146
...	...	@@ -400,13 +402,23 @@
400	402	struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
401	403	int oz_mode = autofs4_oz_mode(sbi);
402	404	int flags = nd ? nd->flags : 0;
403		- int status = 0;
	405	+ int status = 1;
404	406
405	407	/* Pending dentry */
406	408	if (autofs4_ispending(dentry)) {
407		- if (!oz_mode)
408		- status = try_to_fill_dentry(dentry, flags);
409		- return !status;
	409	+ /* The daemon never causes a mount to trigger */
	410	+ if (oz_mode)
	411	+ return 1;
	412	+
	413	+ /*
	414	+ * A zero status is success otherwise we have a
	415	+ * negative error code.
	416	+ */
	417	+ status = try_to_fill_dentry(dentry, flags);
	418	+ if (status == 0)
	419	+ return 1;
	420	+
	421	+ return status;
410	422	}
411	423
412	424	/* Negative dentry.. invalidate if "old" */
...	...	@@ -421,9 +433,19 @@
421	433	DPRINTK("dentry=%p %.*s, emptydir",
422	434	dentry, dentry->d_name.len, dentry->d_name.name);
423	435	spin_unlock(&dcache_lock);
424		- if (!oz_mode)
425		- status = try_to_fill_dentry(dentry, flags);
426		- return !status;
	436	+ /* The daemon never causes a mount to trigger */
	437	+ if (oz_mode)
	438	+ return 1;
	439	+
	440	+ /*
	441	+ * A zero status is success otherwise we have a
	442	+ * negative error code.
	443	+ */
	444	+ status = try_to_fill_dentry(dentry, flags);
	445	+ if (status == 0)
	446	+ return 1;
	447	+
	448	+ return status;
427	449	}
428	450	spin_unlock(&dcache_lock);
429	451
...	...	@@ -372,6 +372,30 @@
372	372	fput(nd->intent.open.file);
373	373	}
374	374
	375	+static inline struct dentry *
	376	+do_revalidate(struct dentry dentry, struct nameidata nd)
	377	+{
	378	+ int status = dentry->d_op->d_revalidate(dentry, nd);
	379	+ if (unlikely(status <= 0)) {
	380	+ /*
	381	+ * The dentry failed validation.
	382	+ * If d_revalidate returned 0 attempt to invalidate
	383	+ * the dentry otherwise d_revalidate is asking us
	384	+ * to return a fail status.
	385	+ */
	386	+ if (!status) {
	387	+ if (!d_invalidate(dentry)) {
	388	+ dput(dentry);
	389	+ dentry = NULL;
	390	+ }
	391	+ } else {
	392	+ dput(dentry);
	393	+ dentry = ERR_PTR(status);
	394	+ }
	395	+ }
	396	+ return dentry;
	397	+}
	398	+
375	399	/*
376	400	* Internal lookup() using the new generic dcache.
377	401	* SMP-safe
...	...	@@ -386,12 +410,9 @@
386	410	if (!dentry)
387	411	dentry = d_lookup(parent, name);
388	412
389		- if (dentry && dentry->d_op && dentry->d_op->d_revalidate) {
390		- if (!dentry->d_op->d_revalidate(dentry, nd) && !d_invalidate(dentry)) {
391		- dput(dentry);
392		- dentry = NULL;
393		- }
394		- }
	413	+ if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
	414	+ dentry = do_revalidate(dentry, nd);
	415	+
395	416	return dentry;
396	417	}
397	418
398	419
...	...	@@ -484,10 +505,9 @@
484	505	*/
485	506	mutex_unlock(&dir->i_mutex);
486	507	if (result->d_op && result->d_op->d_revalidate) {
487		- if (!result->d_op->d_revalidate(result, nd) && !d_invalidate(result)) {
488		- dput(result);
	508	+ result = do_revalidate(result, nd);
	509	+ if (!result)
489	510	result = ERR_PTR(-ENOENT);
490		- }
491	511	}
492	512	return result;
493	513	}
...	...	@@ -767,12 +787,12 @@
767	787	goto done;
768	788
769	789	need_revalidate:
770		- if (dentry->d_op->d_revalidate(dentry, nd))
771		- goto done;
772		- if (d_invalidate(dentry))
773		- goto done;
774		- dput(dentry);
775		- goto need_lookup;
	790	+ dentry = do_revalidate(dentry, nd);
	791	+ if (!dentry)
	792	+ goto need_lookup;
	793	+ if (IS_ERR(dentry))
	794	+ goto fail;
	795	+ goto done;
776	796
777	797	fail:
778	798	return PTR_ERR(dentry);