[PATCH v1 RESEND 01/12] vfs: add a retry_estale helper function to handle retries on ESTALE

[Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

This function is expected to be called from path-based syscalls to help
them decide whether to try the lookup and call again in the event that
they got an -ESTALE return back on an earier try.

Currently, we only retry the call once on an ESTALE error, but in the
event that we decide that that's not enough in the future, we should be
able to change the logic in this helper without too much effort.

Signed-off-by: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 include/linux/fs.h |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8de6755..3c0bcda 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2026,6 +2026,27 @@ extern struct file * dentry_open(struct dentry *, struct vfsmount *, int,
 extern int filp_close(struct file *, fl_owner_t id);
 extern char * getname(const char __user *);
 
+/**
+ * retry_estale - determine whether the caller should retry an operation
+ *
+ * @error: the error we'll be returning
+ * @try: number of retries already performed
+ *
+ * Check to see if the error code was -ESTALE, and then determine whether
+ * to retry the call based on the number of retries so far. Currently, we only
+ * retry the call once.
+ *
+ * Returns true if the caller should try again.
+ */
+static inline bool
+retry_estale(const long error, const unsigned int try)
+{
+	if (likely(error != -ESTALE))
+		return false;
+
+	return !try;
+}
+
 /* fs/ioctl.c */
 
 extern int ioctl_preallocate(struct file *filp, void __user *argp);
-- 
1.7.7.6

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