The patch titled
Subject: proc: calculate end pointer for /proc/*/* lookup at compile time
has been added to the -mm tree. Its filename is
proc-calculate-end-pointer-for-proc-lookup-at-compile-time.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-calculate-end-pointer-for-proc-lookup-at-compile-time.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-calculate-end-pointer-for-proc-lookup-at-compile-time.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Subject: proc: calculate end pointer for /proc/*/* lookup at compile time
Compilers like to transform loops like
for (i = 0; i < n; i++) {
[use p[i]]
}
into
for (p = p0; p < end; p++) {
...
}
Do it by hand, so that it results in overall simpler loop
and smaller code.
Space savings:
$ ./scripts/bloat-o-meter ../vmlinux-001 ../obj/vmlinux
add/remove: 0/0 grow/shrink: 2/1 up/down: 4/-9 (-5)
Function old new delta
proc_tid_base_lookup 17 19 +2
proc_tgid_base_lookup 17 19 +2
proc_pident_lookup 179 170 -9
Note: this trick bloats readdir, so don't do it :-\
Link: http://lkml.kernel.org/r/20190114200422.GB9680@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
--- a/fs/proc/base.c~proc-calculate-end-pointer-for-proc-lookup-at-compile-time
+++ a/fs/proc/base.c
@@ -2446,11 +2446,10 @@ static struct dentry *proc_pident_instan
static struct dentry *proc_pident_lookup(struct inode *dir,
struct dentry *dentry,
- const struct pid_entry *ents,
- unsigned int nents)
+ const struct pid_entry *p,
+ const struct pid_entry *end)
{
struct task_struct *task = get_proc_task(dir);
- const struct pid_entry *p, *last;
struct dentry *res = ERR_PTR(-ENOENT);
if (!task)
@@ -2460,8 +2459,7 @@ static struct dentry *proc_pident_lookup
* Yes, it does not scale. And it should not. Don't add
* new entries into /proc/<tgid>/ without very good reasons.
*/
- last = &ents[nents];
- for (p = ents; p < last; p++) {
+ for (; p < end; p++) {
if (p->len != dentry->d_name.len)
continue;
if (!memcmp(dentry->d_name.name, p->name, p->len)) {
@@ -2600,7 +2598,8 @@ static struct dentry *proc_attr_dir_look
struct dentry *dentry, unsigned int flags)
{
return proc_pident_lookup(dir, dentry,
- attr_dir_stuff, ARRAY_SIZE(attr_dir_stuff));
+ attr_dir_stuff,
+ attr_dir_stuff + ARRAY_SIZE(attr_dir_stuff));
}
static const struct inode_operations proc_attr_dir_inode_operations = {
@@ -3036,7 +3035,8 @@ static const struct file_operations proc
static struct dentry *proc_tgid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
return proc_pident_lookup(dir, dentry,
- tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff));
+ tgid_base_stuff,
+ tgid_base_stuff + ARRAY_SIZE(tgid_base_stuff));
}
static const struct inode_operations proc_tgid_base_inode_operations = {
@@ -3408,7 +3408,8 @@ static int proc_tid_base_readdir(struct
static struct dentry *proc_tid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
return proc_pident_lookup(dir, dentry,
- tid_base_stuff, ARRAY_SIZE(tid_base_stuff));
+ tid_base_stuff,
+ tid_base_stuff + ARRAY_SIZE(tid_base_stuff));
}
static const struct file_operations proc_tid_base_operations = {
_
Patches currently in -mm which might be from adobriyan@xxxxxxxxx are
proc-fix-proc-net-after-setns2.patch
proc-fix-proc-net-after-setns2-v2.patch
mm-shuffle-gfp_-flags.patch
proc-return-exit-code-4-for-skipped-tests.patch
proc-read-kernel-cpu-stat-pointer-once.patch
proc-calculate-end-pointer-for-proc-lookup-at-compile-time.patch
proc-use-seq_puts-everywhere.patch
