#define MAX_ERRNO 1000L
#endif
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,34)
+/* Enable our workaround for a race with d_splice_alias. The race was fixed in
+ * 2.6.34, so don't do it after that point. */
+# define D_SPLICE_ALIAS_RACE
+#endif
+
int cachefs_noreadpage = 0;
extern struct backing_dev_info *afs_backing_dev_info;
return hgetlo(pvcp->f.m.DataVersion);
}
+#ifdef D_SPLICE_ALIAS_RACE
+/* Leave some trace that this code is enabled; otherwise it's pretty hard to
+ * tell. */
+static __attribute__((used)) const char dentry_race_marker[] = "d_splice_alias race workaround enabled";
+
+static int
+check_dentry_race(struct dentry *dp)
+{
+ int raced = 0;
+ if (!dp->d_inode) {
+ struct dentry *parent = dget_parent(dp);
+
+ /* In Linux, before commit 4919c5e45a91b5db5a41695fe0357fbdff0d5767,
+ * d_splice_alias can momentarily hash a dentry before it's fully
+ * populated. This only happens for a moment, since it's unhashed again
+ * right after (in d_move), but this can make the dentry be found by
+ * __d_lookup, and then given to us.
+ *
+ * So check if the dentry is unhashed; if it is, then the dentry is not
+ * valid. We lock the parent inode to ensure that d_splice_alias is no
+ * longer running (the inode mutex will be held during
+ * afs_linux_lookup). Locking d_lock is required to check the dentry's
+ * flags, so lock that, too.
+ */
+ afs_linux_lock_inode(parent->d_inode);
+ spin_lock(&dp->d_lock);
+ if (d_unhashed(dp)) {
+ raced = 1;
+ }
+ spin_unlock(&dp->d_lock);
+ afs_linux_unlock_inode(parent->d_inode);
+
+ dput(parent);
+ }
+ return raced;
+}
+#endif /* D_SPLICE_ALIAS_RACE */
+
/* Validate a dentry. Return 1 if unchanged, 0 if VFS layer should re-evaluate.
* In kernels 2.2.10 and above, we are passed an additional flags var which
* may have either the LOOKUP_FOLLOW OR LOOKUP_DIRECTORY set in which case
return -ECHILD;
#endif
+#ifdef D_SPLICE_ALIAS_RACE
+ if (check_dentry_race(dp)) {
+ valid = 0;
+ return valid;
+ }
+#endif
+
AFS_GLOCK();
afs_InitFakeStat(&fakestate);