• Rasmus Villemoes's avatar
    kernel/trace/blktrace.c: use strreplace() in do_blk_trace_setup() · ff14417c
    Rasmus Villemoes authored
    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>
    ff14417c
blktrace.c 42.3 KB