[Xen-devel] [PATCH v2] tools/xenstore: Do not abort xenstore-ls if a node disappears while iterating

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

From: David Woodhouse <dwmw@xxxxxxxxxxxx>

When recursing, a node sometimes disappears. Deal with it and move on
instead of aborting and failing to print the rest of what was
requested.

Either EACCES or ENOENT may occur as the result of race conditions with
updates; any other error should abort as before.

Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
And thus did an extremely sporadic "not going to delete that device
because it already doesn't exist" failure mode become painfully obvious
in retrospect...

 tools/xenstore/xenstore_client.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/xenstore/xenstore_client.c b/tools/xenstore/xenstore_client.c
index 3afc630ab8..9fcd3d2f9e 100644
--- a/tools/xenstore/xenstore_client.c
+++ b/tools/xenstore/xenstore_client.c
@@ -148,14 +148,20 @@ static void do_ls(struct xs_handle *h, char *path, int 
cur_depth, int show_perms
     int i;
     unsigned int num, len;
 
+    e = xs_directory(h, XBT_NULL, path, &num);
+    if (e == NULL) {
+        if (cur_depth && (errno == ENOENT || errno == EACCES)) {
+            /* If a node disappears while recursing, silently move on. */
+            return;
+        }
+
+        err(1, "xs_directory (%s)", path);
+    }
+
     newpath = malloc(STRING_MAX);
     if (!newpath)
       err(1, "malloc in do_ls");
 
-    e = xs_directory(h, XBT_NULL, path, &num);
-    if (e == NULL)
-        err(1, "xs_directory (%s)", path);
-
     for (i = 0; i<num; i++) {
         char buf[MAX_STRLEN(unsigned int)+1];
         struct xs_permissions *perms;

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