Commit 0b0a0806 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds

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

Commit fc8744ad "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: default avatarHugh Dickins <>
Signed-off-by: default avatarLinus Torvalds <>
parent c15d8a64
......@@ -169,13 +169,13 @@ static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
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))
......@@ -187,13 +187,13 @@ static inline void shmem_unacct_size(unsigned long flags, loff_t size)
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, struct vm_area_struct *vma)
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, int mode, dev_t dev)
info = SHMEM_I(inode);
memset(info, 0, (char *)inode - (char *)info);
info->flags = flags & VM_NORESERVE;
switch (mode & S_IFMT) {
......@@ -1779,9 +1780,10 @@ static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
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,
......@@ -1920,7 +1922,7 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
if (len > PAGE_CACHE_SIZE)
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_block *sb,
sb->s_flags |= MS_POSIXACL;
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, struct page *page)
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_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)
#endif /* CONFIG_SHMEM */
......@@ -2589,7 +2591,7 @@ int shmem_unuse(swp_entry_t entry, struct page *page)
* 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, loff_t size, unsigned long flags)
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;
SHMEM_I(inode)->flags = (flags & VM_NORESERVE) ? 0 : VM_ACCOUNT;
d_instantiate(dentry, inode);
inode->i_size = size;
inode->i_nlink = 0; /* It is unlinked */
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