root/include/linux/shmem_fs.h

DEFINITIONS

1. SHMEM_I
2. shmem_read_mapping_page
3. shmem_fcntl

#ifndef __SHMEM_FS_H
#define __SHMEM_FS_H

#include <linux/file.h>
#include <linux/swap.h>
#include <linux/mempolicy.h>
#include <linux/pagemap.h>
#include <linux/percpu_counter.h>
#include <linux/xattr.h>

/* inode in-kernel data */

struct shmem_inode_info {
        spinlock_t              lock;
        unsigned int            seals;          /* shmem seals */
        unsigned long           flags;
        unsigned long           alloced;        /* data pages alloced to file */
        union {
                unsigned long   swapped;        /* subtotal assigned to swap */
                char            *symlink;       /* unswappable short symlink */
        };
        struct shared_policy    policy;         /* NUMA memory alloc policy */
        struct list_head        swaplist;       /* chain of maybes on swap */
        struct simple_xattrs    xattrs;         /* list of xattrs */
        struct inode            vfs_inode;
};

struct shmem_sb_info {
        unsigned long max_blocks;   /* How many blocks are allowed */
        struct percpu_counter used_blocks;  /* How many are allocated */
        unsigned long max_inodes;   /* How many inodes are allowed */
        unsigned long free_inodes;  /* How many are left for allocation */
        spinlock_t stat_lock;       /* Serialize shmem_sb_info changes */
        kuid_t uid;                 /* Mount uid for root directory */
        kgid_t gid;                 /* Mount gid for root directory */
        umode_t mode;               /* Mount mode for root directory */
        struct mempolicy *mpol;     /* default memory policy for mappings */
};

static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
{
        return container_of(inode, struct shmem_inode_info, vfs_inode);
}

/*
 * Functions in mm/shmem.c called directly from elsewhere:
 */
extern int shmem_init(void);
extern int shmem_fill_super(struct super_block *sb, void *data, int silent);
extern struct file *shmem_file_setup(const char *name,
                                        loff_t size, unsigned long flags);
extern struct file *shmem_kernel_file_setup(const char *name, loff_t size,
                                            unsigned long flags);
extern int shmem_zero_setup(struct vm_area_struct *);
extern int shmem_lock(struct file *file, int lock, struct user_struct *user);
extern bool shmem_mapping(struct address_space *mapping);
extern void shmem_unlock_mapping(struct address_space *mapping);
extern struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
                                        pgoff_t index, gfp_t gfp_mask);
extern void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end);
extern int shmem_unuse(swp_entry_t entry, struct page *page);

static inline struct page *shmem_read_mapping_page(
                                struct address_space *mapping, pgoff_t index)
{
        return shmem_read_mapping_page_gfp(mapping, index,
                                        mapping_gfp_mask(mapping));
}

#ifdef CONFIG_TMPFS

extern int shmem_add_seals(struct file *file, unsigned int seals);
extern int shmem_get_seals(struct file *file);
extern long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg);

#else

static inline long shmem_fcntl(struct file *f, unsigned int c, unsigned long a)
{
        return -EINVAL;
}

#endif

#endif