sysfs: sysfs_add_one WARNs with full path to duplicate filename

sysfs: sysfs_add_one WARNs with full path to duplicate filename

As a debugging aid, it can be useful to know the full path to a
duplicate file being created in sysfs.

We now will display warnings such as:

	sysfs: cannot create duplicate filename '/foo'

when attempting to create multiple files named 'foo' in the sysfs
root, or:

	sysfs: cannot create duplicate filename '/bus/pci/slots/5/foo'

when attempting to create multiple files named 'foo' under a
given directory in sysfs.

The path displayed is always a relative path to sysfs_root. The
leading '/' in the path name refers to the sysfs_root mount
point, and should not be confused with the "real" '/'.

Thanks to Alex Williamson for essentially writing sysfs_pathname.

Cc: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 30 insertions, 2 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 82d3b79d0e08..f13d852ab3c1 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -434,6 +434,26 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
 }
 
 /**
+ *      sysfs_pathname - return full path to sysfs dirent
+ *      @sd: sysfs_dirent whose path we want
+ *      @path: caller allocated buffer
+ *
+ *      Gives the name "/" to the sysfs_root entry; any path returned
+ *      is relative to wherever sysfs is mounted.
+ *
+ *      XXX: does no error checking on @path size
+ */
+static char *sysfs_pathname(struct sysfs_dirent *sd, char *path)
+{
+        if (sd->s_parent) {
+                sysfs_pathname(sd->s_parent, path);
+                strcat(path, "/");
+        }
+        strcat(path, sd->s_name);
+        return path;
+}
+
+/**
  *      sysfs_add_one - add sysfs_dirent to parent
  *      @acxt: addrm context to use
  *      @sd: sysfs_dirent to be added
@@ -458,8 +478,16 @@ int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
         int ret;
 
         ret = __sysfs_add_one(acxt, sd);
-        WARN(ret == -EEXIST, KERN_WARNING "sysfs: duplicate filename '%s' "
-                       "can not be created\n", sd->s_name);
+        if (ret == -EEXIST) {
+                char *path = kzalloc(PATH_MAX, GFP_KERNEL);
+                WARN(1, KERN_WARNING
+                     "sysfs: cannot create duplicate filename '%s'\n",
+                     (path == NULL) ? sd->s_name :
+                     strcat(strcat(sysfs_pathname(acxt->parent_sd, path), "/"),
+                            sd->s_name));
+                kfree(path);
+        }
+
         return ret;
 }