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authorZhen Lei <thunder.leizhen@huawei.com>2020-08-06 23:22:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-07 11:33:26 -0700
commit7bba8f0ea428f8a904c022b86e584009a2f87357 (patch)
treed39baaa8f1c88c4a2ba6bd51761a3acd693e743a /mm/mmap.c
parent2a681cfa5bb41e78e7bfafbb748b581374ce9b1d (diff)
mm/mmap: optimize a branch judgment in ksys_mmap_pgoff()
Look at the pseudo code below. It's very clear that, the judgement "!is_file_hugepages(file)" at 3) is duplicated to the one at 1), we can use "else if" to avoid it. And the assignment "retval = -EINVAL" at 2) is only needed by the branch 3), because "retval" will be overwritten at 4). No functional change, but it can reduce the code size. Maybe more clearer? Before: text data bss dec hex filename 28733 1590 1 30324 7674 mm/mmap.o After: text data bss dec hex filename 28701 1590 1 30292 7654 mm/mmap.o ====pseudo code====: if (!(flags & MAP_ANONYMOUS)) { ... 1) if (is_file_hugepages(file)) len = ALIGN(len, huge_page_size(hstate_file(file))); 2) retval = -EINVAL; 3) if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file))) goto out_fput; } else if (flags & MAP_HUGETLB) { ... } ... 4) retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff); out_fput: ... return retval; Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20200705080112.1405-1-thunder.leizhen@huawei.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index dcdab2675a21..853ae3aebc3d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1562,11 +1562,12 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
file = fget(fd);
if (!file)
return -EBADF;
- if (is_file_hugepages(file))
+ if (is_file_hugepages(file)) {
len = ALIGN(len, huge_page_size(hstate_file(file)));
- retval = -EINVAL;
- if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
+ } else if (unlikely(flags & MAP_HUGETLB)) {
+ retval = -EINVAL;
goto out_fput;
+ }
} else if (flags & MAP_HUGETLB) {
struct user_struct *user = NULL;
struct hstate *hs;