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Commit 3ea2f2b9 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
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perf: Do not waste PAGE_SIZE bytes for ALIGN(8) in perf_event_mmap_event() 



perf_event_mmap_event() does kzalloc(PATH_MAX + sizeof(u64)) to
ensure we can align the size later. However this means that we
actually allocate PAGE_SIZE * 2 buffer, seems too much.

Change this code to allocate PATH_MAX==PAGE_SIZE bytes, but tell
d_path() to not use the last sizeof(u64) bytes.

Note: it is not clear why do we need __GFP_ZERO, see the next patch.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131016201004.GC23214@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 32c5fb7e

kernel/events/core.c

+8 −7
Original line number Diff line number Diff line
@@ -5113,17 +5113,18 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) 
	if (file) {

		struct inode *inode;

		dev_t dev;

		/*

		 * d_path works from the end of the rb backwards, so we

		 * need to add enough zero bytes after the string to handle

		 * the 64bit alignment we do later.

		 */

		buf = kzalloc(PATH_MAX + sizeof(u64), GFP_KERNEL);



		buf = kzalloc(PATH_MAX, GFP_KERNEL);

		if (!buf) {

			name = strncpy(tmp, "//enomem", sizeof(tmp));

			goto got_name;

		}

		name = d_path(&file->f_path, buf, PATH_MAX);

		/*

		 * d_path() works from the end of the rb backwards, so we

		 * need to add enough zero bytes after the string to handle

		 * the 64bit alignment we do later.

		 */

		name = d_path(&file->f_path, buf, PATH_MAX - sizeof(u64));

		if (IS_ERR(name)) {

			name = strncpy(tmp, "//toolong", sizeof(tmp));

			goto got_name;