The patch titled
Subject: kernel/trace/blktrace.c: use strreplace() in do_blk_trace_setup()
has been added to the -mm tree. Its filename is
blktrace-use-strreplace-in-do_blk_trace_setup.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/blktrace-use-strreplace-in-do_blk_trace_setup.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/blktrace-use-strreplace-in-do_blk_trace_setup.patch
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The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/trace/blktrace.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff -puN kernel/trace/blktrace.c~blktrace-use-strreplace-in-do_blk_trace_setup kernel/trace/blktrace.c
--- a/kernel/trace/blktrace.c~blktrace-use-strreplace-in-do_blk_trace_setup
+++ a/kernel/trace/blktrace.c
@@ -439,7 +439,7 @@ int do_blk_trace_setup(struct request_qu
{
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_qu
* 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)
_
Patches currently in -mm which might be from linux@xxxxxxxxxxxxxxxxxx are
linux-slabh-fix-three-off-by-one-typos-in-comment.patch
mm-only-define-hashdist-variable-when-needed.patch
__bitmap_parselist-fix-bug-in-empty-string-handling.patch
lib-sort-add-64-bit-swap-function.patch
lib-sort-add-64-bit-swap-function-v2.patch
lib-sort-add-64-bit-swap-function-v2-fix.patch
lib-string-introduce-strreplace.patch
kernel-trace-trace_events_filterc-use-strreplace.patch
blktrace-use-strreplace-in-do_blk_trace_setup.patch
lib-kobjectc-use-strreplace.patch
drivers-base-corec-use-strreplace.patch
drivers-md-mdc-use-strreplace.patch
fs-jbd2-journalc-use-strreplace.patch
fs-ext4-superc-use-strreplace-in-ext4_fill_super.patch
checkpatch-avoid-not_unified_diff-errors-on-cover-letterpatch-files.patch
linux-next.patch
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