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Date: Tue, 24 Feb 2009 20:51:52 +0000 (GMT)
From: Hugh Dickins <hugh@...itas.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
cc: Andrew Morton <akpm@...ux-foundation.org>,
Matt Mackall <mpm@...enic.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] shmem: fix shared anonymous accounting
Each time I exit Firefox, /proc/meminfo's Committed_AS goes down almost
400 kB: OVERCOMMIT_NEVER would be allowing overcommits it should prohibit.
Commit fc8744adc870a8d4366908221508bb113d8b72ee "Stop playing silly games
with the VM_ACCOUNT flag" changed shmem_file_setup() to set the shmem file's
VM_ACCOUNT flag according to VM_NORESERVE not being set in the vma flags;
but did so only _after_ the shmem_acct_size(flags, size) call which is
expected to pre-account a shared anonymous object.
It's all clearer if we switch shmem.c over to use VM_NORESERVE throughout
in place of !VM_ACCOUNT.
But I very nearly sent in a patch which mistakenly removed the accounting
from tmpfs files: shmem_get_inode()'s memset was good for not setting
VM_ACCOUNT, but now it needs to set VM_NORESERVE.
Rather than setting that by default, then perhaps clearing it again in
shmem_file_setup(), let's pass it as a flag to shmem_get_inode(): that
allows us to remove the #ifdef CONFIG_SHMEM from shmem_file_setup().
Signed-off-by: Hugh Dickins <hugh@...itas.com>
---
mm/shmem.c | 43 +++++++++++++++++++++----------------------
1 file changed, 21 insertions(+), 22 deletions(-)
--- 2.6.29-rc6/mm/shmem.c 2009-02-08 21:25:25.000000000 +0000
+++ linux/mm/shmem.c 2009-02-24 19:48:58.000000000 +0000
@@ -169,13 +169,13 @@ static inline struct shmem_sb_info *SHME
*/
static inline int shmem_acct_size(unsigned long flags, loff_t size)
{
- return (flags & VM_ACCOUNT) ?
- security_vm_enough_memory_kern(VM_ACCT(size)) : 0;
+ return (flags & VM_NORESERVE) ?
+ 0 : security_vm_enough_memory_kern(VM_ACCT(size));
}
static inline void shmem_unacct_size(unsigned long flags, loff_t size)
{
- if (flags & VM_ACCOUNT)
+ if (!(flags & VM_NORESERVE))
vm_unacct_memory(VM_ACCT(size));
}
@@ -187,13 +187,13 @@ static inline void shmem_unacct_size(uns
*/
static inline int shmem_acct_block(unsigned long flags)
{
- return (flags & VM_ACCOUNT) ?
- 0 : security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE));
+ return (flags & VM_NORESERVE) ?
+ security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
}
static inline void shmem_unacct_blocks(unsigned long flags, long pages)
{
- if (!(flags & VM_ACCOUNT))
+ if (flags & VM_NORESERVE)
vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
}
@@ -1515,8 +1515,8 @@ static int shmem_mmap(struct file *file,
return 0;
}
-static struct inode *
-shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
+static struct inode *shmem_get_inode(struct super_block *sb, int mode,
+ dev_t dev, unsigned long flags)
{
struct inode *inode;
struct shmem_inode_info *info;
@@ -1537,6 +1537,7 @@ shmem_get_inode(struct super_block *sb,
info = SHMEM_I(inode);
memset(info, 0, (char *)inode - (char *)info);
spin_lock_init(&info->lock);
+ info->flags = flags & VM_NORESERVE;
INIT_LIST_HEAD(&info->swaplist);
switch (mode & S_IFMT) {
@@ -1779,9 +1780,10 @@ static int shmem_statfs(struct dentry *d
static int
shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
- struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
+ struct inode *inode;
int error = -ENOSPC;
+ inode = shmem_get_inode(dir->i_sb, mode, dev, VM_NORESERVE);
if (inode) {
error = security_inode_init_security(inode, dir, NULL, NULL,
NULL);
@@ -1920,7 +1922,7 @@ static int shmem_symlink(struct inode *d
if (len > PAGE_CACHE_SIZE)
return -ENAMETOOLONG;
- inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
+ inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
if (!inode)
return -ENOSPC;
@@ -2332,7 +2334,7 @@ static int shmem_fill_super(struct super
sb->s_flags |= MS_POSIXACL;
#endif
- inode = shmem_get_inode(sb, S_IFDIR | sbinfo->mode, 0);
+ inode = shmem_get_inode(sb, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
if (!inode)
goto failed;
inode->i_uid = sbinfo->uid;
@@ -2574,12 +2576,12 @@ int shmem_unuse(swp_entry_t entry, struc
return 0;
}
-#define shmem_file_operations ramfs_file_operations
-#define shmem_vm_ops generic_file_vm_ops
-#define shmem_get_inode ramfs_get_inode
-#define shmem_acct_size(a, b) 0
-#define shmem_unacct_size(a, b) do {} while (0)
-#define SHMEM_MAX_BYTES LLONG_MAX
+#define shmem_vm_ops generic_file_vm_ops
+#define shmem_file_operations ramfs_file_operations
+#define shmem_get_inode(sb, mode, dev, flags) ramfs_get_inode(sb, mode, dev)
+#define shmem_acct_size(flags, size) 0
+#define shmem_unacct_size(flags, size) do {} while (0)
+#define SHMEM_MAX_BYTES LLONG_MAX
#endif /* CONFIG_SHMEM */
@@ -2589,7 +2591,7 @@ int shmem_unuse(swp_entry_t entry, struc
* shmem_file_setup - get an unlinked file living in tmpfs
* @name: name for dentry (to be seen in /proc/<pid>/maps
* @size: size to be set for the file
- * @flags: vm_flags
+ * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
*/
struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
{
@@ -2623,13 +2625,10 @@ struct file *shmem_file_setup(char *name
goto put_dentry;
error = -ENOSPC;
- inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
+ inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0, flags);
if (!inode)
goto close_file;
-#ifdef CONFIG_SHMEM
- SHMEM_I(inode)->flags = (flags & VM_NORESERVE) ? 0 : VM_ACCOUNT;
-#endif
d_instantiate(dentry, inode);
inode->i_size = size;
inode->i_nlink = 0; /* It is unlinked */
--
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