Commit ff14417c authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Linus Torvalds

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: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Liked-by: default avatarJens Axboe <axboe@fb.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1bb56471
...@@ -439,7 +439,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, ...@@ -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 blk_trace *old_bt, *bt = NULL;
struct dentry *dir = NULL; struct dentry *dir = NULL;
int ret, i; int ret;
if (!buts->buf_size || !buts->buf_nr) if (!buts->buf_size || !buts->buf_nr)
return -EINVAL; return -EINVAL;
...@@ -451,9 +451,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, ...@@ -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 * some device names have larger paths - convert the slashes
* to underscores for this to work as expected * to underscores for this to work as expected
*/ */
for (i = 0; i < strlen(buts->name); i++) strreplace(buts->name, '/', '_');
if (buts->name[i] == '/')
buts->name[i] = '_';
bt = kzalloc(sizeof(*bt), GFP_KERNEL); bt = kzalloc(sizeof(*bt), GFP_KERNEL);
if (!bt) if (!bt)
......
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