linux-kernel - [PATCH V2] mm/cma_debug: show complete cma name in debugfs directories

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Date:   Thu, 11 Aug 2022 18:45:29 +0530
From:   Charan Teja Kalla <quic_charante@...cinc.com>
To:     <akpm@...ux-foundation.org>, <david@...hat.com>, <vbabka@...e.cz>,
        <quic_pkondeti@...cinc.com>, <minchan@...nel.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Charan Teja Kalla <quic_charante@...cinc.com>
Subject: [PATCH V2] mm/cma_debug: show complete cma name in debugfs directories

Currently only 12 characters of the cma name is being used as the debug
directories where as the cma name can be of length CMA_MAX_NAME(=64)
characters. One side problem with this is having 2 cma's with first
common 12 characters would end up in trying to create directories with
same name and fails with -EEXIST thus can limit cma debug functionality.

The 'cma-' prefix is used initially where cma areas don't have any names
and are represented by simple integer values. Since now each cma would
be having its own name, drop 'cma-' prefix for the cma debug directories
as they are clearly evident that they are for cma debug through creating
them in /sys/kernel/debug/cma/ path.

Signed-off-by: Charan Teja Kalla <quic_charante@...cinc.com>
---
V2:
 o Updated the cma_debugfs.rst documentation.
Vl:
 o https://lore.kernel.org/all/1660152485-17684-1-git-send-email-quic_charante@quicinc.com/

 Documentation/admin-guide/mm/cma_debugfs.rst | 10 +++++-----
 mm/cma_debug.c                               |  5 +----
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/Documentation/admin-guide/mm/cma_debugfs.rst b/Documentation/admin-guide/mm/cma_debugfs.rst
index 4e06ffa..7367e62 100644
--- a/Documentation/admin-guide/mm/cma_debugfs.rst
+++ b/Documentation/admin-guide/mm/cma_debugfs.rst
@@ -5,10 +5,10 @@ CMA Debugfs Interface
 The CMA debugfs interface is useful to retrieve basic information out of the
 different CMA areas and to test allocation/release in each of the areas.
 
-Each CMA zone represents a directory under <debugfs>/cma/, indexed by the
-kernel's CMA index. So the first CMA zone would be:
+Each CMA area represents a directory under <debugfs>/cma/, represented by
+its CMA name like below:
 
-	<debugfs>/cma/cma-0
+	<debugfs>/cma/<cma_name>
 
 The structure of the files created under that directory is as follows:
 
@@ -18,8 +18,8 @@ The structure of the files created under that directory is as follows:
  - [RO] bitmap: The bitmap of page states in the zone.
  - [WO] alloc: Allocate N pages from that CMA area. For example::
 
-	echo 5 > <debugfs>/cma/cma-2/alloc
+	echo 5 > <debugfs>/cma/<cma_name>/alloc
 
-would try to allocate 5 pages from the cma-2 area.
+would try to allocate 5 pages from the 'cma_name' area.
 
  - [WO] free: Free N pages from that CMA area, similar to the above.
diff --git a/mm/cma_debug.c b/mm/cma_debug.c
index 2e77049..602fff8 100644
--- a/mm/cma_debug.c
+++ b/mm/cma_debug.c
@@ -163,11 +163,8 @@ DEFINE_DEBUGFS_ATTRIBUTE(cma_alloc_fops, NULL, cma_alloc_write, "%llu\n");
 static void cma_debugfs_add_one(struct cma *cma, struct dentry *root_dentry)
 {
 	struct dentry *tmp;
-	char name[16];
 
-	scnprintf(name, sizeof(name), "cma-%s", cma->name);
-
-	tmp = debugfs_create_dir(name, root_dentry);
+	tmp = debugfs_create_dir(cma->name, root_dentry);
 
 	debugfs_create_file("alloc", 0200, tmp, cma, &cma_alloc_fops);
 	debugfs_create_file("free", 0200, tmp, cma, &cma_free_fops);
-- 
2.7.4