diff options
| author | Mateusz Guzik <mjguzik@gmail.com> | 2025-03-01 11:43:56 +0100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-03-05 18:25:36 +0100 |
| commit | 23e490336467fcdaf95e1efcf8f58067b59f647b (patch) | |
| tree | b7c1de648d05cb960b86cd0150a98815c35c6836 /fs/open.c | |
| parent | 2014c95afecee3e76ca4a56956a936e23283f05b (diff) | |
fs: predict no error in close()
Vast majority of the time the system call returns 0.
Letting the compiler know shortens the routine (119 -> 116) and the fast
path.
Disasm starting at the call to __fput_sync():
before:
<+55>: call 0xffffffff816b0da0 <__fput_sync>
<+60>: lea 0x201(%rbx),%eax
<+66>: cmp $0x1,%eax
<+69>: jbe 0xffffffff816ab707 <__x64_sys_close+103>
<+71>: mov %ebx,%edx
<+73>: movslq %ebx,%rax
<+76>: and $0xfffffffd,%edx
<+79>: cmp $0xfffffdfc,%edx
<+85>: mov $0xfffffffffffffffc,%rdx
<+92>: cmove %rdx,%rax
<+96>: pop %rbx
<+97>: pop %rbp
<+98>: jmp 0xffffffff82242fa0 <__x86_return_thunk>
<+103>: mov $0xfffffffffffffffc,%rax
<+110>: jmp 0xffffffff816ab700 <__x64_sys_close+96>
<+112>: mov $0xfffffffffffffff7,%rax
<+119>: jmp 0xffffffff816ab700 <__x64_sys_close+96>
after:
<+56>: call 0xffffffff816b0da0 <__fput_sync>
<+61>: xor %eax,%eax
<+63>: test %ebp,%ebp
<+65>: jne 0xffffffff816ab6ea <__x64_sys_close+74>
<+67>: pop %rbx
<+68>: pop %rbp
<+69>: jmp 0xffffffff82242fa0 <__x86_return_thunk> # the jmp out
<+74>: lea 0x201(%rbp),%edx
<+80>: mov $0xfffffffffffffffc,%rax
<+87>: cmp $0x1,%edx
<+90>: jbe 0xffffffff816ab6e3 <__x64_sys_close+67>
<+92>: mov %ebp,%edx
<+94>: and $0xfffffffd,%edx
<+97>: cmp $0xfffffdfc,%edx
<+103>: cmovne %rbp,%rax
<+107>: jmp 0xffffffff816ab6e3 <__x64_sys_close+67>
<+109>: mov $0xfffffffffffffff7,%rax
<+116>: jmp 0xffffffff816ab6e3 <__x64_sys_close+67>
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20250301104356.246031-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/open.c')
| -rw-r--r-- | fs/open.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/fs/open.c b/fs/open.c index 932e5a6de63b..a8a5f843e3cf 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1578,11 +1578,14 @@ SYSCALL_DEFINE1(close, unsigned int, fd) */ __fput_sync(file); + if (likely(retval == 0)) + return 0; + /* can't restart close syscall because file table entry was cleared */ - if (unlikely(retval == -ERESTARTSYS || - retval == -ERESTARTNOINTR || - retval == -ERESTARTNOHAND || - retval == -ERESTART_RESTARTBLOCK)) + if (retval == -ERESTARTSYS || + retval == -ERESTARTNOINTR || + retval == -ERESTARTNOHAND || + retval == -ERESTART_RESTARTBLOCK) retval = -EINTR; return retval; |