LU-9868 llite: handle DCACHE_PAR_LOOKUP in ll_dcompare

[fs/lustre-release.git] / lustre / llite / dcache.c

diff --git a/lustre/llite/dcache.c b/lustre/llite/dcache.c
index 6a026f0..5790afb 100644 (file)
--- a/lustre/llite/dcache.c
+++ b/lustre/llite/dcache.c
@@ -77,7 +77,14 @@ static void ll_release(struct dentry *de)
  * This avoids a race where ll_lookup_it() instantiates a dentry, but we get
  * an AST before calling d_revalidate_it().  The dentry still exists (marked
  * INVALID) so d_lookup() matches it, but we have no lock on it (so
- * lock_match() fails) and we spin around real_lookup(). */
+ * lock_match() fails) and we spin around real_lookup().
+ *
+ * This race doesn't apply to lookups in d_alloc_parallel(), and for
+ * those we want to ensure that only one dentry with a given name is
+ * in ll_lookup_nd() at a time.  So allow invalid dentries to match
+ * while d_in_lookup().  We will be called again when the lookup
+ * completes, and can give a different answer then.
+ */
 #ifdef HAVE_D_COMPARE_7ARGS
 static int ll_dcompare(const struct dentry *parent, const struct inode *pinode,
                       const struct dentry *dentry, const struct inode *inode,
@@ -117,6 +124,10 @@ static int ll_dcompare(struct dentry *parent, struct qstr *d_name,
        if (d_mountpoint((struct dentry *)dentry))
                RETURN(0);
 
+       /* ensure exclusion against parallel lookup of the same name */
+       if (d_in_lookup((struct dentry *)dentry))
+               return 0;
+
        if (d_lustre_invalid(dentry))
                RETURN(1);