Patch "mtd: Avoid probe failures when mtd->dbg.dfs_dir is invalid" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

    mtd: Avoid probe failures when mtd->dbg.dfs_dir is invalid

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mtd-avoid-probe-failures-when-mtd-dbg.dfs_dir-is-invalid.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Boris Brezillon <[email protected]>
Date: Sat, 11 Nov 2017 16:08:34 +0100
Subject: mtd: Avoid probe failures when mtd->dbg.dfs_dir is invalid

From: Boris Brezillon <[email protected]>

commit 1530578abdac4edce9244c7a1962ded3ffdb58ce upstream.

Commit e8e3edb95ce6 ("mtd: create per-device and module-scope debugfs entries") tried to make MTD related debugfs stuff consistent across the MTD framework by creating a root <debugfs>/mtd/ directory containing one directory per MTD device.

The problem is that, by default, the MTD layer only registers the master device if no partitions are defined for this master. This behavior breaks all drivers that expect mtd->dbg.dfs_dir to be filled correctly after calling mtd_device_register() in order to add their own debugfs entries.

The only way we can force all MTD masters to be registered no matter if they expose partitions or not is by enabling the CONFIG_MTD_PARTITIONED_MASTER option.

In such situations, there's no other solution but to accept skipping debugfs initialization when dbg.dfs_dir is invalid, and when this happens, inform the user that he should consider enabling CONFIG_MTD_PARTITIONED_MASTER.

---
 drivers/mtd/devices/docg3.c |    7 ++++++-
 drivers/mtd/nand/nandsim.c  |   13 +++++++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

@@ -1814,8 +1814,13 @@ static void __init doc_dbg_register(stru
 	struct dentry *root = floor->dbg.dfs_dir;
 	struct docg3 *docg3 = floor->priv;
 
-	if (IS_ERR_OR_NULL(root))
+	if (IS_ERR_OR_NULL(root)) {
+		if (IS_ENABLED(CONFIG_DEBUG_FS) &&
+		    !IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))
+			dev_warn(floor->dev.parent,
+				 "CONFIG_MTD_PARTITIONED_MASTER must be enabled to expose debugfs stuff\n");
 		return;
+	}
 
 	debugfs_create_file("docg3_flashcontrol", S_IRUSR, root, docg3,
 			    &flashcontrol_fops);

@@ -520,11 +520,16 @@ static int nandsim_debugfs_create(struct
 	struct dentry *root = nsmtd->dbg.dfs_dir;
 	struct dentry *dent;
 
-	if (!IS_ENABLED(CONFIG_DEBUG_FS))
+	/*
+	 * Just skip debugfs initialization when the debugfs directory is
+	 * missing.
+	 */
+	if (IS_ERR_OR_NULL(root)) {
+		if (IS_ENABLED(CONFIG_DEBUG_FS) &&
+		    !IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))
+			NS_WARN("CONFIG_MTD_PARTITIONED_MASTER must be enabled to expose debugfs stuff\n");
 		return 0;
-
-	if (IS_ERR_OR_NULL(root))
-		return -1;
+	}
 
 	dent = debugfs_create_file("nandsim_wear_report", S_IRUSR,
 				   root, dev, &dfs_fops);

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/mtd-nand-fix-writing-mtdoops-to-nand-flash.patch queue-4.14/mtd-nand-export-nand_reset-symbol.patch queue-4.14/mtd-nand-mtk-fix-infinite-ecc-decode-irq-issue.patch queue-4.14/mtd-nand-atmel-actually-use-the-pm-ops.patch queue-4.14/mtd-nand-omap2-fix-subpage-write.patch queue-4.14/mtd-avoid-probe-failures-when-mtd-dbg.dfs_dir-is-invalid.patch