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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2015-06-25 15:02:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-25 17:00:40 -0700
commitff14417c0a00c9a906b4ba79fbecb79bd2435207 (patch)
tree5dd37412bb97ada4dea19c6dc0a01eacd1da3c49
parent1bb564718f298dfd7c435819d3bc902e6be666c6 (diff)
downloadlinux-linaro-stable-ff14417c0a00c9a906b4ba79fbecb79bd2435207.tar.gz
kernel/trace/blktrace.c: use strreplace() in do_blk_trace_setup()
Part of the disassembly of do_blk_trace_setup: 231b: e8 00 00 00 00 callq 2320 <do_blk_trace_setup+0x50> 231c: R_X86_64_PC32 strlen+0xfffffffffffffffc 2320: eb 0a jmp 232c <do_blk_trace_setup+0x5c> 2322: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1) 2328: 48 83 c3 01 add $0x1,%rbx 232c: 48 39 d8 cmp %rbx,%rax 232f: 76 47 jbe 2378 <do_blk_trace_setup+0xa8> 2331: 41 80 3c 1c 2f cmpb $0x2f,(%r12,%rbx,1) 2336: 75 f0 jne 2328 <do_blk_trace_setup+0x58> 2338: 41 c6 04 1c 5f movb $0x5f,(%r12,%rbx,1) 233d: 4c 89 e7 mov %r12,%rdi 2340: e8 00 00 00 00 callq 2345 <do_blk_trace_setup+0x75> 2341: R_X86_64_PC32 strlen+0xfffffffffffffffc 2345: eb e1 jmp 2328 <do_blk_trace_setup+0x58> Yep, that's right: gcc isn't smart enough to realize that replacing '/' by '_' cannot change the strlen(), so we call it again and again (at least when a '/' is found). Even if gcc were that smart, this construction would still loop over the string twice, once for the initial strlen() call and then the open-coded loop. Let's simply use strreplace() instead. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Acked-by: Steven Rostedt <rostedt@goodmis.org> Liked-by: Jens Axboe <axboe@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/trace/blktrace.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 483cecfa5c17..4eeae4674b5a 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -439,7 +439,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
{
struct blk_trace *old_bt, *bt = NULL;
struct dentry *dir = NULL;
- int ret, i;
+ int ret;
if (!buts->buf_size || !buts->buf_nr)
return -EINVAL;
@@ -451,9 +451,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
* some device names have larger paths - convert the slashes
* to underscores for this to work as expected
*/
- for (i = 0; i < strlen(buts->name); i++)
- if (buts->name[i] == '/')
- buts->name[i] = '_';
+ strreplace(buts->name, '/', '_');
bt = kzalloc(sizeof(*bt), GFP_KERNEL);
if (!bt)