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Subject[PATCH] 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 :-\

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

fs/proc/base.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2459,11 +2459,10 @@ static struct dentry *proc_pident_instantiate(struct dentry *dentry,

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)
@@ -2473,8 +2472,7 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
* 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)) {
@@ -2613,7 +2611,8 @@ static struct dentry *proc_attr_dir_lookup(struct inode *dir,
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 = {
@@ -3049,7 +3048,8 @@ static const struct file_operations proc_tgid_base_operations = {
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 = {
@@ -3421,7 +3421,8 @@ static int proc_tid_base_readdir(struct file *file, struct dir_context *ctx)
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 = {
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