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mm/cma_debug: show complete cma name in debugfs directories
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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.

Link: https://lkml.kernel.org/r/1660223729-22461-1-git-send-email-quic_charante@quicinc.com
Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Pavan Kondeti <quic_pkondeti@quicinc.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Charan Teja Kalla authored and Andrew Morton committed Sep 12, 2022
1 parent cf1e3fe commit 9a79443
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10 changes: 5 additions & 5 deletions Documentation/admin-guide/mm/cma_debugfs.rst
Original file line number Diff line number Diff line change
Expand Up @@ -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:

Expand All @@ -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.
5 changes: 1 addition & 4 deletions mm/cma_debug.c
Original file line number Diff line number Diff line change
Expand Up @@ -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[CMA_MAX_NAME];

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);
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