commit cfbb71ecbe5ab3096ca5e33cc3396e57d5f224bb
Author: Erez_Zadok <[EMAIL PROTECTED]>
Date: Sat Nov 17 22:33:46 2007 -0500
Unionfs: unionfs_lookup locking consistency
Ensure that our lookup locking is consistent and symmetric: if a lock
existed before calling lookup_backend, it should remain so; only if
performing a lookup of a known new dentry, should lookup_backend return a
newly-locked dentry-inode info (and only if there was no error). Document
this behavior. This cleanup allowed us to remove two unnecessary int
declarations.
Signed-off-by: Erez Zadok <[EMAIL PROTECTED]>
diff --git a/fs/unionfs/inode.c b/fs/unionfs/inode.c
index eace050..2ebf7d8 100644
--- a/fs/unionfs/inode.c
+++ b/fs/unionfs/inode.c
@@ -151,7 +151,10 @@ static struct dentry *unionfs_lookup(struct inode *parent,
path_save.mnt = nd->mnt;
}
- /* The locking is done by unionfs_lookup_backend. */
+ /*
+ * unionfs_lookup_backend returns a locked dentry upon success,
+ * so we'll have to unlock it below.
+ */
ret = unionfs_lookup_backend(dentry, nd, INTERPOSE_LOOKUP);
/* restore the dentry & vfsmnt in namei */
@@ -164,6 +167,7 @@ static struct dentry *unionfs_lookup(struct inode *parent,
dentry = ret;
/* parent times may have changed */
unionfs_copy_attr_times(dentry->d_parent->d_inode);
+ unionfs_unlock_dentry(dentry);
}
unionfs_check_inode(parent);
diff --git a/fs/unionfs/lookup.c b/fs/unionfs/lookup.c
index e820c31..92f7f3b 100644
--- a/fs/unionfs/lookup.c
+++ b/fs/unionfs/lookup.c
@@ -27,6 +27,11 @@ static int realloc_dentry_private_data(struct dentry
*dentry);
*
* Returns: NULL (ok), ERR_PTR if an error occurred, or a non-null non-error
* PTR if d_splice returned a different dentry.
+ *
+ * If lookupmode is INTERPOSE_PARTIAL/REVAL/REVAL_NEG, the passed dentry's
+ * inode info must be locked. If lookupmode is INTERPOSE_LOOKUP (i.e., a
+ * newly looked-up dentry), then unionfs_lookup_backend will return a locked
+ * dentry's info, which the caller must unlock.
*/
struct dentry *unionfs_lookup_backend(struct dentry *dentry,
struct nameidata *nd, int lookupmode)
@@ -43,8 +48,6 @@ struct dentry *unionfs_lookup_backend(struct dentry *dentry,
struct dentry *first_lower_dentry = NULL;
struct vfsmount *first_lower_mnt = NULL;
int locked_parent = 0;
- int locked_child = 0;
- int allocated_new_info = 0;
const char *name;
int namelen;
struct nameidata new_nd;
@@ -57,24 +60,21 @@ struct dentry *unionfs_lookup_backend(struct dentry *dentry,
if (lookupmode == INTERPOSE_PARTIAL || lookupmode == INTERPOSE_REVAL ||
lookupmode == INTERPOSE_REVAL_NEG)
verify_locked(dentry);
- else {
+ else /* this could only be INTERPOSE_LOOKUP */
BUG_ON(UNIONFS_D(dentry) != NULL);
- locked_child = 1;
- }
- switch(lookupmode) {
- case INTERPOSE_PARTIAL:
- break;
- case INTERPOSE_LOOKUP:
- if ((err = new_dentry_private_data(dentry)))
- goto out;
- allocated_new_info = 1;
- break;
- default:
- if ((err = realloc_dentry_private_data(dentry)))
- goto out;
- allocated_new_info = 1;
- break;
+ switch (lookupmode) {
+ case INTERPOSE_PARTIAL:
+ break;
+ case INTERPOSE_LOOKUP:
+ if ((err = new_dentry_private_data(dentry)))
+ goto out;
+ break;
+ default:
+ /* default: can only be INTERPOSE_REVAL/REVAL_NEG */
+ if ((err = realloc_dentry_private_data(dentry)))
+ goto out;
+ break;
}
/* must initialize dentry operations */
@@ -352,7 +352,7 @@ out:
if (locked_parent)
unionfs_unlock_dentry(parent_dentry);
dput(parent_dentry);
- if (locked_child || (err && allocated_new_info))
+ if (err && (lookupmode == INTERPOSE_LOOKUP))
unionfs_unlock_dentry(dentry);
if (!err && d_interposed)
return d_interposed;
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