From d30cae217b9c1e02c2c144a810b1448722761a19 Mon Sep 17 00:00:00 2001
From: Antonio SJ Musumeci <trapexit@spawn.link>
Date: Sat, 7 Feb 2015 18:27:47 -0500
Subject: [PATCH] add user.mergerfs.allpaths and user.mergerfs.relpath to
 getxattr

---
 README.md        | 11 +++++++++--
 src/fs.cpp       | 21 +++++++++++++++++++++
 src/fs.hpp       |  4 ++++
 src/getxattr.cpp | 49 +++++++++++++++++++++++++++++++++++++++++++-----
 4 files changed, 78 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 9b5b1afb..d968191e 100644
--- a/README.md
+++ b/README.md
@@ -148,8 +148,10 @@ For **user.mergerfs.srcmounts** there are several instructions available for man
 
 While they won't show up when using [listxattr](http://linux.die.net/man/2/listxattr) mergerfs offers a number of special xattrs to query information about the files served. To access the values you will need to issue a [getxattr](http://linux.die.net/man/2/getxattr) for one of the following:
 
-* user.mergerfs.basepath : gives you the base mount point for the file given the current search policy
-* user.mergerfs.fullpath : gives you the full path of the original file given the search policy
+* user.mergerfs.basepath: the base mount point for the file given the current search policy
+* user.mergerfs.relpath: the relative path of the file from the perspective of the mount point
+* user.mergerfs.fullpath: the full path of the original file given the search policy
+* user.mergerfs.allpaths: a NUL ('\0') separated list of full paths to all files found
 
 ```
 [trapexit:/tmp/mount] $ ls
@@ -158,4 +160,9 @@ A B C
 /mnt/a/full/path/to/A
 [trapexit:/tmp/mount] $ xattr -p user.mergerfs.basepath A
 /mnt/a
+[trapexit:/tmp/mount] $ xattr -p user.mergerfs.relpath A
+/full/path/to/A
+[trapexit:/tmp/mount] $ xattr -p user.mergerfs.allpaths A | tr '\0' '\n'
+/mnt/a/full/path/to/A
+/mnt/b/full/path/to/A
 ```
diff --git a/src/fs.cpp b/src/fs.cpp
index 76813f88..93f18b7c 100644
--- a/src/fs.cpp
+++ b/src/fs.cpp
@@ -162,6 +162,27 @@ namespace fs
                        fusepath);
   }
 
+  void
+  findallfiles(const vector<string> &srcmounts,
+               const string         &fusepath,
+               vector<string>       &paths)
+  {
+    for(vector<string>::const_iterator
+          iter = srcmounts.begin(), eiter = srcmounts.end();
+        iter != eiter;
+        ++iter)
+      {
+        int rv;
+        string fullpath;
+        struct stat st;
+
+        fullpath = fs::make_path(*iter,fusepath);
+        rv = ::lstat(fullpath.c_str(),&st);
+        if(rv == 0)
+          paths.push_back(fullpath);
+      }
+  }
+
   int
   listxattr(const string &path,
             vector<char> &attrs)
diff --git a/src/fs.hpp b/src/fs.hpp
index e87a0ff6..588b960a 100644
--- a/src/fs.hpp
+++ b/src/fs.hpp
@@ -64,6 +64,10 @@ namespace fs
   bool path_exists(const vector<string>           &srcmounts,
                    const string                   &fusepath);
 
+  void findallfiles(const vector<string> &srcmounts,
+                    const string         &fusepath,
+                    vector<string>       &paths);
+
   int clonepath(const string &srcfrom,
                 const string &srcto,
                 const string &relative);
diff --git a/src/getxattr.cpp b/src/getxattr.cpp
index 5e1c4dfd..a67529c4 100644
--- a/src/getxattr.cpp
+++ b/src/getxattr.cpp
@@ -94,6 +94,46 @@ _getxattr_from_string(char         *destbuf,
   return srcbufsize;
 }
 
+static
+int
+_getxattr_user_mergerfs_allpaths(const vector<string> &srcmounts,
+                                 const string         &fusepath,
+                                 char                 *buf,
+                                 const size_t          count)
+{
+  string concated;
+  vector<string> paths;
+
+  fs::findallfiles(srcmounts,fusepath,paths);
+
+  concated = str::join(paths,'\0');
+
+  return ::_getxattr_from_string(buf,count,concated);
+}
+
+static
+int
+_getxattr_user_mergerfs(const fs::Path       &path,
+                        const vector<string> &srcmounts,
+                        const string         &fusepath,
+                        const char           *attrname,
+                        char                 *buf,
+                        const size_t          count)
+{
+  const char *attrbasename = &attrname[sizeof("user.mergerfs")];
+
+  if(!strcmp(attrbasename,"basepath"))
+    return ::_getxattr_from_string(buf,count,path.base);
+  else if(!strcmp(attrbasename,"fullpath"))
+    return ::_getxattr_from_string(buf,count,path.full);
+  else if(!strcmp(attrbasename,"relpath"))
+    return ::_getxattr_from_string(buf,count,fusepath);
+  else if(!strcmp(attrbasename,"allpaths"))
+    return ::_getxattr_user_mergerfs_allpaths(srcmounts,fusepath,buf,count);
+
+  return (errno=ENOATTR,-1);
+}
+
 static
 int
 _getxattr(const fs::SearchFunc  searchFunc,
@@ -111,11 +151,10 @@ _getxattr(const fs::SearchFunc  searchFunc,
   if(rv == -1)
     return -errno;
 
-  if(!strcmp(attrname,"user.mergerfs.basepath"))
-    rv = ::_getxattr_from_string(buf,count,path.base);
-  else if(!strcmp(attrname,"user.mergerfs.fullpath"))
-    rv = ::_getxattr_from_string(buf,count,path.full);
-  else
+  if(!strncmp("user.mergerfs.",attrname,sizeof("user.mergerfs.")-1))
+    rv = _getxattr_user_mergerfs(path,srcmounts,fusepath,attrname,buf,count);
+
+  if(rv == -1 && errno == ENOATTR)
     rv = ::lgetxattr(path.full.c_str(),attrname,buf,count);
 
   return ((rv == -1) ? -errno : rv);