Here's another try at this.
On Tue, 20 Jun 2006, Andrew Morton wrote:
> On Wed, 21 Jun 2006 14:18:15 +0800
> Ian Kent <[email protected]> wrote:
>
> >
> > Hi Andrew,
> >
> > I didn't get any adverse (or other feedback) for this patch after posting
> > an RFC to LKML so here it is.
> >
> > 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.
> >
snip ...
>
> Also, did you consider broadening the ->d_revalidate() semantics? It
> appears that all implementations return 0 or 1. You could teach the VFS to
> also recognise and act upon a -ve return value, and do this trickery within
> the autofs d_revalidate(), perhaps?
>
Yep and I've now done this.
I think this is in fact the only way to do it.
Signed-off-by: Ian Kent <[email protected]>
--
--- linux-2.6.17-mm1/include/linux/dcache.h.dcache-revalidate-return-fail 2006-06-22 11:51:18.000000000 +0800
+++ linux-2.6.17-mm1/include/linux/dcache.h 2006-06-22 11:51:38.000000000 +0800
@@ -175,7 +175,6 @@ d_iput: no no no yes
#define DCACHE_UNHASHED 0x0010
#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */
-#define DCACHE_REVAL_FORCE_FAIL 0x0040 /* Force revalidate fail on valid dentry */
extern spinlock_t dcache_lock;
--- linux-2.6.17-mm1/fs/autofs4/root.c.dcache-revalidate-return-fail 2006-06-22 11:54:24.000000000 +0800
+++ linux-2.6.17-mm1/fs/autofs4/root.c 2006-06-22 22:50:32.000000000 +0800
@@ -137,7 +137,9 @@ static int autofs4_dir_open(struct inode
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 @@ static int autofs4_revalidate(struct den
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" */
@@ -421,16 +433,19 @@ static int autofs4_revalidate(struct den
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);
- if (status) {
- spin_lock(&dentry->d_lock);
- dentry->d_flags |= DCACHE_REVAL_FORCE_FAIL;
- spin_unlock(&dentry->d_lock);
- return 0;
- }
- }
- 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);
--- linux-2.6.17-mm1/fs/namei.c.dcache-revalidate-return-fail 2006-06-22 11:50:13.000000000 +0800
+++ linux-2.6.17-mm1/fs/namei.c 2006-06-22 13:01:02.000000000 +0800
@@ -365,6 +365,29 @@ void release_open_intent(struct nameidat
fput(nd->intent.open.file);
}
+static __always_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
@@ -379,27 +402,9 @@ static struct dentry * cached_lookup(str
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)) {
- if (!d_invalidate(dentry)) {
- dput(dentry);
- return NULL;
- }
- /*
- * As well as the normal validation, check if we need
- * to force a fail on a valid dentry (autofs4 browsable
- * mounts).
- */
- spin_lock(&dentry->d_lock);
- if (dentry->d_flags & DCACHE_REVAL_FORCE_FAIL) {
- dentry->d_flags &= ~DCACHE_REVAL_FORCE_FAIL;
- spin_unlock(&dentry->d_lock);
- dput(dentry);
- return ERR_PTR(-ENOENT);
- }
- spin_unlock(&dentry->d_lock);
- }
- }
+ if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
+ dentry = do_revalidate(dentry, nd);
+
return dentry;
}
@@ -492,25 +497,9 @@ static struct dentry * real_lookup(struc
*/
mutex_unlock(&dir->i_mutex);
if (result->d_op && result->d_op->d_revalidate) {
- if (!result->d_op->d_revalidate(result, nd)) {
- if (!d_invalidate(result)) {
- dput(result);
- return ERR_PTR(-ENOENT);
- }
- /*
- * d_revalidate failed but the dentry is still valid so
- * check if we need to force a fail on the dentry (autofs4
- * browsable mounts).
- */
- spin_lock(&result->d_lock);
- if (result->d_flags & DCACHE_REVAL_FORCE_FAIL) {
- result->d_flags &= ~DCACHE_REVAL_FORCE_FAIL;
- spin_unlock(&result->d_lock);
- dput(result);
- return ERR_PTR(-ENOENT);
- }
- spin_unlock(&result->d_lock);
- }
+ result = do_revalidate(result, nd);
+ if (!result)
+ result = ERR_PTR(-ENOENT);
}
return result;
}
@@ -790,25 +779,12 @@ need_lookup:
goto done;
need_revalidate:
- if (dentry->d_op->d_revalidate(dentry, nd))
- goto done;
- if (d_invalidate(dentry)) {
- /*
- * d_revalidate failed but the dentry is still valid so check
- * if we need to return a fail (autofs4 browsable mounts).
- */
- spin_lock(&dentry->d_lock);
- if (dentry->d_flags & DCACHE_REVAL_FORCE_FAIL) {
- dentry->d_flags &= ~DCACHE_REVAL_FORCE_FAIL;
- spin_unlock(&dentry->d_lock);
- dput(dentry);
- return -ENOENT;
- }
- spin_unlock(&dentry->d_lock);
- 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);
-
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