[PATCH] One more -x to not traverse cyclic bind-mounts

[Jeff Hansen]

This patch allows one to repeat the '-x' option a third time to stop rsync from traversing potentially cyclic bind mounts that are on the same filesystem.

su
cd
mkdir ~/cycle
touch ~/cycle/file.txt
mkdir ~/cycle/cycle
mount -o bind ~/cycle ~/cycle/cycle
rsync -avxx ~/cycle ~/cycle2



-Jeff

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//Jeff Hansen
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--- ./rsync.1.orig	2011-01-13 11:10:23.000000000 -0700
+++ ./rsync.1	2011-01-13 11:12:37.000000000 -0700
@@ -1255,6 +1255,10 @@
 the copy.  Otherwise, it includes an empty directory at each mount-point it
 encounters (using the attributes of the mounted directory because those of
 the underlying mount-point directory are inaccessible).
+.IP
+If this option is repeated twice, rsync omits all mount-point directories,
+even if it is the same filesystem, as is potentially the case in a cyclic
+bind mount.
 .IP 
 If rsync has been told to collapse symlinks (via \fB\-\-copy\-links\fP or
 \fB\-\-copy\-unsafe\-links\fP), a symlink to a directory on another device is
--- ./rsync.yo.orig	2011-01-13 11:07:53.000000000 -0700
+++ ./rsync.yo	2011-01-13 11:12:44.000000000 -0700
@@ -1096,6 +1096,10 @@
 encounters (using the attributes of the mounted directory because those of
 the underlying mount-point directory are inaccessible).
 
+If this option is repeated twice, rsync omits all mount-point directories,
+even if it is the same filesystem, as is potentially the case in a cyclic 
+bind mount.
+
 If rsync has been told to collapse symlinks (via bf(--copy-links) or
 bf(--copy-unsafe-links)), a symlink to a directory on another device is
 treated like a mount-point.  Symlinks to non-directories are unaffected
--- ./flist.c.orig	2011-01-13 10:59:03.000000000 -0700
+++ ./flist.c	2011-01-13 11:06:55.000000000 -0700
@@ -1153,9 +1153,10 @@
 		/* -x only affects dirs because we need to avoid recursing
 		 * into a mount-point directory, not to avoid copying a
 		 * symlinked file if -L (or similar) was specified. */
-		if (one_file_system && st.st_dev != filesystem_dev
+		if (one_file_system
 		 && BITS_SETnUNSET(flags, FLAG_CONTENT_DIR, FLAG_TOP_DIR)) {
-			if (one_file_system > 1) {
+			if (one_file_system > 2) {
+ofs_skip:
 				if (verbose > 1) {
 					rprintf(FINFO,
 					    "[%s] skipping mount-point dir %s\n",
@@ -1163,8 +1164,12 @@
 				}
 				return NULL;
 			}
-			flags |= FLAG_MOUNT_DIR;
-			flags &= ~FLAG_CONTENT_DIR;
+			if (st.st_dev != filesystem_dev) {
+				if (one_file_system > 1)
+					goto ofs_skip;
+				flags |= FLAG_MOUNT_DIR;
+				flags &= ~FLAG_CONTENT_DIR;
+			}
 		}
 	} else
 		flags &= ~FLAG_CONTENT_DIR;
--- ./options.c.orig	2011-01-13 11:19:20.000000000 -0700
+++ ./options.c	2011-01-13 11:19:30.000000000 -0700
@@ -1808,6 +1808,8 @@
 		argstr[x++] = 'x';
 		if (one_file_system > 1)
 			argstr[x++] = 'x';
+		if (one_file_system > 2)
+			argstr[x++] = 'x';
 	}
 	if (sparse_files)
 		argstr[x++] = 'S';

For example, the following scenario would cyclically traverse the bind mounts until the OS (Linux in this case) hits a maximum traversal count, thank goodness. Other OSes may traverse the bind mount indefinitely... Please let me if there is any feedback on this patch and when/if this patch can be merged. Thanks!

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