On 06/08/2015 05:26 PM, Rasmus Villemoes wrote:
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.
Patch looks fine to me, but there's no strreplace in in Linus' tree. Dependencies like that should be noted in the patch. Please send followup patches like this when the main patch is in Linus tree, and I'd be happy to apply it.
-- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
