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proc: move "struct proc_dir_entry" into kmem cache

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"struct proc_dir_entry" is variable sized because of 0-length trailing
array for name, however, because of SLAB padding allocations it is
possible to make "struct proc_dir_entry" fixed sized and allocate same
amount of memory.

It buys fine-grained debugging with poisoning and usercopy protection
which is not possible with kmalloc-* caches.

Currently, on 32-bit 91+ byte allocations go into kmalloc-128 and on
64-bit 147+ byte allocations go to kmalloc-192 anyway.

Additional memory is allocated only for 38/46+ byte long names which are
rare or may not even exist in the wild.

Link: http://lkml.kernel.org/r/20180223205504.GA17139@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan
2018-04-10 16:31:52 -07:00
committed by Linus Torvalds
parent c4219edf1d
commit b4884f2333
5 changed files with 52 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
fs/proc/generic.c
View File

@@ -8,6 +8,7 @@
* Copyright (C) 1997 Theodore Ts'o
*/
#include <linux/cache.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
@@ -28,6 +29,17 @@
static DEFINE_RWLOCK(proc_subdir_lock);
struct kmem_cache *proc_dir_entry_cache __ro_after_init;
void pde_free(struct proc_dir_entry *pde)
{
if (S_ISLNK(pde->mode))
kfree(pde->data);
if (pde->name != pde->inline_name)
kfree(pde->name);
kmem_cache_free(proc_dir_entry_cache, pde);
}
static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int len)
{
if (len < de->namelen)
@@ -363,10 +375,20 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
return NULL;
}
ent = kzalloc(sizeof(struct proc_dir_entry) + qstr.len + 1, GFP_KERNEL);
ent = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);
if (!ent)
goto out;
if (qstr.len + 1 <= sizeof(ent->inline_name)) {
ent->name = ent->inline_name;
} else {
ent->name = kmalloc(qstr.len + 1, GFP_KERNEL);
if (!ent->name) {
pde_free(ent);
return NULL;
}
}
memcpy(ent->name, fn, qstr.len + 1);
ent->namelen = qstr.len;
ent->mode = mode;
@@ -395,12 +417,11 @@ struct proc_dir_entry *proc_symlink(const char *name,
strcpy((char*)ent->data,dest);
ent->proc_iops = &proc_link_inode_operations;
if (proc_register(parent, ent) < 0) {
kfree(ent->data);
kfree(ent);
pde_free(ent);
ent = NULL;
}
} else {
kfree(ent);
pde_free(ent);
ent = NULL;
}
}
@@ -423,7 +444,7 @@ struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
ent->proc_iops = &proc_dir_inode_operations;
parent->nlink++;
if (proc_register(parent, ent) < 0) {
kfree(ent);
pde_free(ent);
parent->nlink--;
ent = NULL;
}
@@ -458,7 +479,7 @@ struct proc_dir_entry *proc_create_mount_point(const char *name)
ent->proc_iops = NULL;
parent->nlink++;
if (proc_register(parent, ent) < 0) {
kfree(ent);
pde_free(ent);
parent->nlink--;
ent = NULL;
}
@@ -495,7 +516,7 @@ struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
goto out_free;
return pde;
out_free:
kfree(pde);
pde_free(pde);
out:
return NULL;
}
@@ -522,19 +543,12 @@ void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
}
EXPORT_SYMBOL(proc_set_user);
static void free_proc_entry(struct proc_dir_entry *de)
{
proc_free_inum(de->low_ino);
if (S_ISLNK(de->mode))
kfree(de->data);
kfree(de);
}
void pde_put(struct proc_dir_entry *pde)
{
if (atomic_dec_and_test(&pde->count))
free_proc_entry(pde);
if (atomic_dec_and_test(&pde->count)) {
proc_free_inum(pde->low_ino);
pde_free(pde);
}
}
/*