linux-kernel - Re: [PATCH] sysfs: sysfs_add_one tells you _where

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Message-ID: <20090212175659.GC20654@ldl.fc.hp.com>
Date:	Thu, 12 Feb 2009 10:56:59 -0700
From:	Alex Chiang <achiang@...com>
To:	Greg KH <gregkh@...e.de>
Cc:	Kay Sievers <kay.sievers@...y.org>, arjan@...ux.intel.com,
	alex.williamson@...com, linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sysfs: sysfs_add_one tells you _where_ the duplicate
	file is

* Greg KH <gregkh@...e.de>:
> On Thu, Feb 12, 2009 at 10:38:35AM -0700, Alex Chiang wrote:
> > +	if (ret == -EEXIST) {
> > +		char *path = kzalloc(PATH_MAX, GFP_KERNEL);
> 
> You forgot to check the return value of kzalloc().
> 
> Another try?
> 
> 8th time's a charm?  :)

Yeah, you're too fast for me. I thought about that just as I
walked away from my desk. ;)

What are we on, v6?

From: Alex Chiang <achiang@...com>

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@...com>
Signed-off-by: Alex Chiang <achiang@...com>
---
 dir.c |   32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)
---
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 82d3b79..f13d852 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;
 }
 
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