| Message ID | 20250416221626.2710239-3-mjguzik@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | two nits for path lookup | expand |
diff --git a/include/linux/device_cgroup.h b/include/linux/device_cgroup.h index d02f32b7514e..0864773a57e8 100644 --- a/include/linux/device_cgroup.h +++ b/include/linux/device_cgroup.h @@ -18,15 +18,16 @@ static inline int devcgroup_inode_permission(struct inode *inode, int mask) { short type, access = 0; + if (likely(!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))) + return 0; + if (likely(!inode->i_rdev)) return 0; if (S_ISBLK(inode->i_mode)) type = DEVCG_DEV_BLOCK; - else if (S_ISCHR(inode->i_mode)) + else /* S_ISCHR by the test above */ type = DEVCG_DEV_CHAR; - else - return 0; if (mask & MAY_WRITE) access |= DEVCG_ACC_WRITE;
The routine gets called for every path component during lookup. ->i_mode is going to be cached on account of permission checks, while ->i_rdev is an area which is most likely cache-cold. gcc 14.2 is kind enough to emit one branch: movzwl (%rbx),%eax mov %eax,%edx and $0xb000,%dx cmp $0x2000,%dx je 11bc <inode_permission+0xec> This patch is lazy in that I don't know if the ->i_rdev branch makes any sense with the newly added mode check upfront. I am not changing any semantics here though. Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> --- include/linux/device_cgroup.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)