cregit-Linux how code gets into the kernel

Release 4.12 include/linux/fs.h

Directory: include/linux
#ifndef _LINUX_FS_H

#define _LINUX_FS_H

#include <linux/linkage.h>
#include <linux/wait.h>
#include <linux/kdev_t.h>
#include <linux/dcache.h>
#include <linux/path.h>
#include <linux/stat.h>
#include <linux/cache.h>
#include <linux/list.h>
#include <linux/list_lru.h>
#include <linux/llist.h>
#include <linux/radix-tree.h>
#include <linux/rbtree.h>
#include <linux/init.h>
#include <linux/pid.h>
#include <linux/bug.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/capability.h>
#include <linux/semaphore.h>
#include <linux/fiemap.h>
#include <linux/rculist_bl.h>
#include <linux/atomic.h>
#include <linux/shrinker.h>
#include <linux/migrate_mode.h>
#include <linux/uidgid.h>
#include <linux/lockdep.h>
#include <linux/percpu-rwsem.h>
#include <linux/workqueue.h>
#include <linux/delayed_call.h>

#include <asm/byteorder.h>
#include <uapi/linux/fs.h>

struct backing_dev_info;
struct bdi_writeback;
struct bio;
struct export_operations;
struct hd_geometry;
struct iovec;
struct kiocb;
struct kobject;
struct pipe_inode_info;
struct poll_table_struct;
struct kstatfs;
struct vm_area_struct;
struct vfsmount;
struct cred;
struct swap_info_struct;
struct seq_file;
struct workqueue_struct;
struct iov_iter;
struct fscrypt_info;
struct fscrypt_operations;

extern void __init inode_init(void);
extern void __init inode_init_early(void);
extern void __init files_init(void);
extern void __init files_maxfiles_init(void);

extern struct files_stat_struct files_stat;
extern unsigned long get_max_files(void);
extern unsigned int sysctl_nr_open;
extern struct inodes_stat_t inodes_stat;
extern int leases_enable, lease_break_time;
extern int sysctl_protected_symlinks;
extern int sysctl_protected_hardlinks;

struct buffer_head;

typedef int (get_block_t)(struct inode *inode, sector_t iblock,
			struct buffer_head *bh_result, int create);

typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
			ssize_t bytes, void *private);


#define MAY_EXEC		0x00000001

#define MAY_WRITE		0x00000002

#define MAY_READ		0x00000004

#define MAY_APPEND		0x00000008

#define MAY_ACCESS		0x00000010

#define MAY_OPEN		0x00000020

#define MAY_CHDIR		0x00000040
/* called from RCU mode, don't block */

#define MAY_NOT_BLOCK		0x00000080

/*
 * flags in file.f_mode.  Note that FMODE_READ and FMODE_WRITE must correspond
 * to O_WRONLY and O_RDWR via the strange trick in __dentry_open()
 */

/* file is open for reading */

#define FMODE_READ		((__force fmode_t)0x1)
/* file is open for writing */

#define FMODE_WRITE		((__force fmode_t)0x2)
/* file is seekable */

#define FMODE_LSEEK		((__force fmode_t)0x4)
/* file can be accessed using pread */

#define FMODE_PREAD		((__force fmode_t)0x8)
/* file can be accessed using pwrite */

#define FMODE_PWRITE		((__force fmode_t)0x10)
/* File is opened for execution with sys_execve / sys_uselib */

#define FMODE_EXEC		((__force fmode_t)0x20)
/* File is opened with O_NDELAY (only set for block devices) */

#define FMODE_NDELAY		((__force fmode_t)0x40)
/* File is opened with O_EXCL (only set for block devices) */

#define FMODE_EXCL		((__force fmode_t)0x80)
/* File is opened using open(.., 3, ..) and is writeable only for ioctls
   (specialy hack for floppy.c) */

#define FMODE_WRITE_IOCTL	((__force fmode_t)0x100)
/* 32bit hashes as llseek() offset (for directories) */

#define FMODE_32BITHASH         ((__force fmode_t)0x200)
/* 64bit hashes as llseek() offset (for directories) */

#define FMODE_64BITHASH         ((__force fmode_t)0x400)

/*
 * Don't update ctime and mtime.
 *
 * Currently a special hack for the XFS open_by_handle ioctl, but we'll
 * hopefully graduate it to a proper O_CMTIME flag supported by open(2) soon.
 */

#define FMODE_NOCMTIME		((__force fmode_t)0x800)

/* Expect random access pattern */

#define FMODE_RANDOM		((__force fmode_t)0x1000)

/* File is huge (eg. /dev/kmem): treat loff_t as unsigned */

#define FMODE_UNSIGNED_OFFSET	((__force fmode_t)0x2000)

/* File is opened with O_PATH; almost nothing can be done with it */

#define FMODE_PATH		((__force fmode_t)0x4000)

/* File needs atomic accesses to f_pos */

#define FMODE_ATOMIC_POS	((__force fmode_t)0x8000)
/* Write access to underlying fs */

#define FMODE_WRITER		((__force fmode_t)0x10000)
/* Has read method(s) */

#define FMODE_CAN_READ          ((__force fmode_t)0x20000)
/* Has write method(s) */

#define FMODE_CAN_WRITE         ((__force fmode_t)0x40000)

/* File was opened by fanotify and shouldn't generate fanotify events */

#define FMODE_NONOTIFY		((__force fmode_t)0x4000000)

/*
 * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector
 * that indicates that they should check the contents of the iovec are
 * valid, but not check the memory that the iovec elements
 * points too.
 */

#define CHECK_IOVEC_ONLY -1

/*
 * Attribute flags.  These should be or-ed together to figure out what
 * has been changed!
 */

#define ATTR_MODE	(1 << 0)

#define ATTR_UID	(1 << 1)

#define ATTR_GID	(1 << 2)

#define ATTR_SIZE	(1 << 3)

#define ATTR_ATIME	(1 << 4)

#define ATTR_MTIME	(1 << 5)

#define ATTR_CTIME	(1 << 6)

#define ATTR_ATIME_SET	(1 << 7)

#define ATTR_MTIME_SET	(1 << 8)

#define ATTR_FORCE	(1 << 9) 
/* Not a change, but a change it */

#define ATTR_ATTR_FLAG	(1 << 10)

#define ATTR_KILL_SUID	(1 << 11)

#define ATTR_KILL_SGID	(1 << 12)

#define ATTR_FILE	(1 << 13)

#define ATTR_KILL_PRIV	(1 << 14)

#define ATTR_OPEN	(1 << 15) 
/* Truncating from open(O_TRUNC) */

#define ATTR_TIMES_SET	(1 << 16)

#define ATTR_TOUCH	(1 << 17)

/*
 * Whiteout is represented by a char device.  The following constants define the
 * mode and device number to use.
 */

#define WHITEOUT_MODE 0

#define WHITEOUT_DEV 0

/*
 * This is the Inode Attributes structure, used for notify_change().  It
 * uses the above definitions as flags, to know which values have changed.
 * Also, in this manner, a Filesystem can look at only the values it cares
 * about.  Basically, these are the attributes that the VFS layer can
 * request to change from the FS layer.
 *
 * Derek Atkins <warlord@MIT.EDU> 94-10-20
 */

struct iattr {
	
unsigned int	ia_valid;
	
umode_t		ia_mode;
	
kuid_t		ia_uid;
	
kgid_t		ia_gid;
	
loff_t		ia_size;
	
struct timespec	ia_atime;
	
struct timespec	ia_mtime;
	
struct timespec	ia_ctime;

	/*
         * Not an attribute, but an auxiliary info for filesystems wanting to
         * implement an ftruncate() like method.  NOTE: filesystem should
         * check for (ia_valid & ATTR_FILE), and not for (ia_file != NULL).
         */
	
struct file	*ia_file;
};

/*
 * Includes for diskquotas.
 */
#include <linux/quota.h>

/*
 * Maximum number of layers of fs stack.  Needs to be limited to
 * prevent kernel stack overflow
 */

#define FILESYSTEM_MAX_STACK_DEPTH 2

/** 
 * enum positive_aop_returns - aop return codes with specific semantics
 *
 * @AOP_WRITEPAGE_ACTIVATE: Informs the caller that page writeback has
 *                          completed, that the page is still locked, and
 *                          should be considered active.  The VM uses this hint
 *                          to return the page to the active list -- it won't
 *                          be a candidate for writeback again in the near
 *                          future.  Other callers must be careful to unlock
 *                          the page if they get this return.  Returned by
 *                          writepage(); 
 *
 * @AOP_TRUNCATED_PAGE: The AOP method that was handed a locked page has
 *                      unlocked it and the page might have been truncated.
 *                      The caller should back up to acquiring a new page and
 *                      trying again.  The aop will be taking reasonable
 *                      precautions not to livelock.  If the caller held a page
 *                      reference, it should drop it before retrying.  Returned
 *                      by readpage().
 *
 * address_space_operation functions return these large constants to indicate
 * special semantics to the caller.  These are much larger than the bytes in a
 * page to allow for functions that return the number of bytes operated on in a
 * given page.
 */


enum positive_aop_returns {
	
AOP_WRITEPAGE_ACTIVATE	= 0x80000,
	
AOP_TRUNCATED_PAGE	= 0x80001,
};


#define AOP_FLAG_CONT_EXPAND		0x0001 
/* called from cont_expand */

#define AOP_FLAG_NOFS			0x0002 
/* used by filesystem to direct
                                                * helper code (eg buffer layer)
                                                * to clear GFP_FS from alloc */

/*
 * oh the beauties of C type declarations.
 */
struct page;
struct address_space;
struct writeback_control;


#define IOCB_EVENTFD		(1 << 0)

#define IOCB_APPEND		(1 << 1)

#define IOCB_DIRECT		(1 << 2)

#define IOCB_HIPRI		(1 << 3)

#define IOCB_DSYNC		(1 << 4)

#define IOCB_SYNC		(1 << 5)

#define IOCB_WRITE		(1 << 6)


struct kiocb {
	
struct file		*ki_filp;
	
loff_t			ki_pos;
	
void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
	
void			*private;
	
int			ki_flags;
};




static inline bool is_sync_kiocb(struct kiocb *kiocb)
{
	return kiocb->ki_complete == NULL;
}


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static inline int iocb_flags(struct file *file);




static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
{
	*kiocb = (struct kiocb) {
		.ki_filp = filp,
		.ki_flags = iocb_flags(filp),
        };
}


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/*
 * "descriptor" for what we're up to with a read.
 * This allows us to use the same read code yet
 * have multiple different users of the data that
 * we read from a file.
 *
 * The simplest case just copies the data to user
 * mode.
 */
typedef struct {
	
size_t written;
	
size_t count;
	union {
		
char __user *buf;
		
void *data;
	
} arg;
	
int error;

} read_descriptor_t;


typedef int (*read_actor_t)(read_descriptor_t *, struct page *,
		unsigned long, unsigned long);


struct address_space_operations {
	
int (*writepage)(struct page *page, struct writeback_control *wbc);
	
int (*readpage)(struct file *, struct page *);

	/* Write back some dirty pages from this mapping. */
	
int (*writepages)(struct address_space *, struct writeback_control *);

	/* Set a page dirty.  Return true if this dirtied it */
	
int (*set_page_dirty)(struct page *page);

	
int (*readpages)(struct file *filp, struct address_space *mapping,
			struct list_head *pages, unsigned nr_pages);

	
int (*write_begin)(struct file *, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned flags,
				struct page **pagep, void **fsdata);
	
int (*write_end)(struct file *, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned copied,
				struct page *page, void *fsdata);

	/* Unfortunately this kludge is needed for FIBMAP. Don't use it */
	
sector_t (*bmap)(struct address_space *, sector_t);
	
void (*invalidatepage) (struct page *, unsigned int, unsigned int);
	
int (*releasepage) (struct page *, gfp_t);
	
void (*freepage)(struct page *);
	
ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
	/*
         * migrate the contents of a page to the specified target. If
         * migrate_mode is MIGRATE_ASYNC, it must not block.
         */
	
int (*migratepage) (struct address_space *,
			struct page *, struct page *, enum migrate_mode);
	
bool (*isolate_page)(struct page *, isolate_mode_t);
	
void (*putback_page)(struct page *);
	
int (*launder_page) (struct page *);
	
int (*is_partially_uptodate) (struct page *, unsigned long,
					unsigned long);
	
void (*is_dirty_writeback) (struct page *, bool *, bool *);
	
int (*error_remove_page)(struct address_space *, struct page *);

	/* swapfile support */
	
int (*swap_activate)(struct swap_info_struct *sis, struct file *file,
				sector_t *span);
	
void (*swap_deactivate)(struct file *file);
};

extern const struct address_space_operations empty_aops;

/*
 * pagecache_write_begin/pagecache_write_end must be used by general code
 * to write into the pagecache.
 */
int pagecache_write_begin(struct file *, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned flags,
				struct page **pagep, void **fsdata);

int pagecache_write_end(struct file *, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned copied,
				struct page *page, void *fsdata);


struct address_space {
	
struct inode		*host;		/* owner: inode, block_device */
	
struct radix_tree_root	page_tree;	/* radix tree of all pages */
	
spinlock_t		tree_lock;	/* and lock protecting it */
	
atomic_t		i_mmap_writable;/* count VM_SHARED mappings */
	
struct rb_root		i_mmap;		/* tree of private and shared mappings */
	
struct rw_semaphore	i_mmap_rwsem;	/* protect tree, count, list */
	/* Protected by tree_lock together with the radix tree */
	
unsigned long		nrpages;	/* number of total pages */
	/* number of shadow or DAX exceptional entries */
	
unsigned long		nrexceptional;
	
pgoff_t			writeback_index;/* writeback starts here */
	
const struct address_space_operations *a_ops;	/* methods */
	
unsigned long		flags;		/* error bits */
	
spinlock_t		private_lock;	/* for use by the address_space */
	
gfp_t			gfp_mask;	/* implicit gfp mask for allocations */
	
struct list_head	private_list;	/* ditto */
	
void			*private_data;	/* ditto */
} __attribute__((aligned(sizeof(long))));
	/*
         * On most architectures that alignment is already the case; but
         * must be enforced here for CRIS, to let the least significant bit
         * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON.
         */
struct request_queue;


struct block_device {
	
dev_t			bd_dev;  /* not a kdev_t - it's a search key */
	
int			bd_openers;
	
struct inode *		bd_inode;	/* will die */
	
struct super_block *	bd_super;
	
struct mutex		bd_mutex;	/* open/close mutex */
	
void *			bd_claiming;
	
void *			bd_holder;
	
int			bd_holders;
	
bool			bd_write_holder;
#ifdef CONFIG_SYSFS
	
struct list_head	bd_holder_disks;
#endif
	
struct block_device *	bd_contains;
	
unsigned		bd_block_size;
	
struct hd_struct *	bd_part;
	/* number of times partitions within this device have been opened. */
	
unsigned		bd_part_count;
	
int			bd_invalidated;
	
struct gendisk *	bd_disk;
	
struct request_queue *  bd_queue;
	
struct backing_dev_info *bd_bdi;
	
struct list_head	bd_list;
	/*
         * Private data.  You must have bd_claim'ed the block_device
         * to use this.  NOTE:  bd_claim allows an owner to claim
         * the same device multiple times, the owner must take special
         * care to not mess up bd_private for that case.
         */
	
unsigned long		bd_private;

	/* The counter of freeze processes */
	
int			bd_fsfreeze_count;
	/* Mutex for freeze */
	
struct mutex		bd_fsfreeze_mutex;
};

/*
 * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
 * radix trees
 */

#define PAGECACHE_TAG_DIRTY	0

#define PAGECACHE_TAG_WRITEBACK	1

#define PAGECACHE_TAG_TOWRITE	2

int mapping_tagged(struct address_space *mapping, int tag);




static inline void i_mmap_lock_write(struct address_space *mapping)
{
	down_write(&mapping->i_mmap_rwsem);
}


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static inline void i_mmap_unlock_write(struct address_space *mapping)
{
	up_write(&mapping->i_mmap_rwsem);
}


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static inline void i_mmap_lock_read(struct address_space *mapping)
{
	down_read(&mapping->i_mmap_rwsem);
}


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static inline void i_mmap_unlock_read(struct address_space *mapping)
{
	up_read(&mapping->i_mmap_rwsem);
}


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/*
 * Might pages of this file be mapped into userspace?
 */



static inline int mapping_mapped(struct address_space *mapping)
{
	return	!RB_EMPTY_ROOT(&mapping->i_mmap);
}


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/*
 * Might pages of this file have been modified in userspace?
 * Note that i_mmap_writable counts all VM_SHARED vmas: do_mmap_pgoff
 * marks vma as VM_SHARED if it is shared, and the file was opened for
 * writing i.e. vma may be mprotected writable even if now readonly.
 *
 * If i_mmap_writable is negative, no new writable mappings are allowed. You
 * can only deny writable mappings, if none exists right now.
 */



static inline int mapping_writably_mapped(struct address_space *mapping)
{
	return atomic_read(&mapping->i_mmap_writable) > 0;
}


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static inline int mapping_map_writable(struct address_space *mapping)
{
	return atomic_inc_unless_negative(&mapping->i_mmap_writable) ?
		0 : -EPERM;
}


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static inline void mapping_unmap_writable(struct address_space *mapping)
{
	atomic_dec(&mapping->i_mmap_writable);
}


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static inline int mapping_deny_writable(struct address_space *mapping)
{
	return atomic_dec_unless_positive(&mapping->i_mmap_writable) ?
		0 : -EBUSY;
}


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static inline void mapping_allow_writable(struct address_space *mapping)
{
	atomic_inc(&mapping->i_mmap_writable);
}


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/*
 * Use sequence counter to get consistent i_size on 32-bit processors.
 */
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
#include <linux/seqlock.h>

#define __NEED_I_SIZE_ORDERED

#define i_size_ordered_init(inode) seqcount_init(&inode->i_size_seqcount)
#else

#define i_size_ordered_init(inode) do { } while (0)
#endif

struct posix_acl;

#define ACL_NOT_CACHED ((void *)(-1))

#define ACL_DONT_CACHE ((void *)(-3))



static inline struct posix_acl *

uncached_acl_sentinel(struct task_struct *task)
{
	return (void *)task + 1;
}


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static inline bool

is_uncached_acl(struct posix_acl *acl)
{
	return (long)acl & 1;
}


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#define IOP_FASTPERM	0x0001

#define IOP_LOOKUP	0x0002

#define IOP_NOFOLLOW	0x0004

#define IOP_XATTR	0x0008

#define IOP_DEFAULT_READLINK	0x0010

struct fsnotify_mark_connector;

/*
 * Keep mostly read-only and often accessed (especially for
 * the RCU path lookup and 'stat' data) fields at the beginning
 * of the 'struct inode'
 */

struct inode {
	
umode_t			i_mode;
	
unsigned short		i_opflags;
	
kuid_t			i_uid;
	
kgid_t			i_gid;
	
unsigned int		i_flags;

#ifdef CONFIG_FS_POSIX_ACL
	
struct posix_acl	*i_acl;
	
struct posix_acl	*i_default_acl;
#endif

	
const struct inode_operations	*i_op;
	
struct super_block	*i_sb;
	
struct address_space	*i_mapping;

#ifdef CONFIG_SECURITY
	
void			*i_security;
#endif

	/* Stat data, not accessed from path walking */
	
unsigned long		i_ino;
	/*
         * Filesystems may only read i_nlink directly.  They shall use the
         * following functions for modification:
         *
         *    (set|clear|inc|drop)_nlink
         *    inode_(inc|dec)_link_count
         */
	union {
		
const unsigned int i_nlink;
		
unsigned int __i_nlink;
	};
	
dev_t			i_rdev;
	
loff_t			i_size;
	
struct timespec		i_atime;
	
struct timespec		i_mtime;
	
struct timespec		i_ctime;
	
spinlock_t		i_lock;	/* i_blocks, i_bytes, maybe i_size */
	
unsigned short          i_bytes;
	
unsigned int		i_blkbits;
	
blkcnt_t		i_blocks;

#ifdef __NEED_I_SIZE_ORDERED
	
seqcount_t		i_size_seqcount;
#endif

	/* Misc */
	
unsigned long		i_state;
	
struct rw_semaphore	i_rwsem;

	
unsigned long		dirtied_when;	/* jiffies of first dirtying */
	
unsigned long		dirtied_time_when;

	
struct hlist_node	i_hash;
	
struct list_head	i_io_list;	/* backing dev IO list */
#ifdef CONFIG_CGROUP_WRITEBACK
	
struct bdi_writeback	*i_wb;		/* the associated cgroup wb */

	/* foreign inode detection, see wbc_detach_inode() */
	
int			i_wb_frn_winner;
	
u16			i_wb_frn_avg_time;
	
u16			i_wb_frn_history;
#endif
	
struct list_head	i_lru;		/* inode LRU list */
	
struct list_head	i_sb_list;
	
struct list_head	i_wb_list;	/* backing dev writeback list */
	union {
		
struct hlist_head	i_dentry;
		
struct rcu_head		i_rcu;
	};
	
u64			i_version;
	
atomic_t		i_count;
	
atomic_t		i_dio_count;
	
atomic_t		i_writecount;
#ifdef CONFIG_IMA
	
atomic_t		i_readcount; /* struct files open RO */
#endif
	
const struct file_operations	*i_fop;	/* former ->i_op->default_file_ops */
	
struct file_lock_context	*i_flctx;
	
struct address_space	i_data;
	
struct list_head	i_devices;
	union {
		
struct pipe_inode_info	*i_pipe;
		
struct block_device	*i_bdev;
		
struct cdev		*i_cdev;
		
char			*i_link;
		
unsigned		i_dir_seq;
	};

	
__u32			i_generation;

#ifdef CONFIG_FSNOTIFY
	
__u32			i_fsnotify_mask; /* all events this inode cares about */
	
struct fsnotify_mark_connector __rcu	*i_fsnotify_marks;
#endif

#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
	
struct fscrypt_info	*i_crypt_info;
#endif

	
void			*i_private; /* fs or device private pointer */
};




static inline unsigned int i_blocksize(const struct inode *node)
{
	return (1 << node->i_blkbits);
}


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static inline int inode_unhashed(struct inode *inode)
{
	return hlist_unhashed(&inode->i_hash);
}


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/*
 * inode->i_mutex nesting subclasses for the lock validator:
 *
 * 0: the object of the current VFS operation
 * 1: parent
 * 2: child/target
 * 3: xattr
 * 4: second non-directory
 * 5: second parent (when locking independent directories in rename)
 *
 * I_MUTEX_NONDIR2 is for certain operations (such as rename) which lock two
 * non-directories at once.
 *
 * The locking order between these classes is
 * parent[2] -> child -> grandchild -> normal -> xattr -> second non-directory
 */

enum inode_i_mutex_lock_class
{
	
I_MUTEX_NORMAL,
	
I_MUTEX_PARENT,
	
I_MUTEX_CHILD,
	
I_MUTEX_XATTR,
	
I_MUTEX_NONDIR2,
	
I_MUTEX_PARENT2,
};




static inline void inode_lock(struct inode *inode)
{
	down_write(&inode->i_rwsem);
}


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static inline void inode_unlock(struct inode *inode)
{
	up_write(&inode->i_rwsem);
}


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static inline void inode_lock_shared(struct inode *inode)
{
	down_read(&inode->i_rwsem);
}


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static inline void inode_unlock_shared(struct inode *inode)
{
	up_read(&inode->i_rwsem);
}


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static inline int inode_trylock(struct inode *inode)
{
	return down_write_trylock(&inode->i_rwsem);
}


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static inline int inode_trylock_shared(struct inode *inode)
{
	return down_read_trylock(&inode->i_rwsem);
}


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static inline int inode_is_locked(struct inode *inode)
{
	return rwsem_is_locked(&inode->i_rwsem);
}


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static inline void inode_lock_nested(struct inode *inode, unsigned subclass)
{
	down_write_nested(&inode->i_rwsem, subclass);
}


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void lock_two_nondirectories(struct inode *, struct inode*);
void unlock_two_nondirectories(struct inode *, struct inode*);

/*
 * NOTE: in a 32bit arch with a preemptable kernel and
 * an UP compile the i_size_read/write must be atomic
 * with respect to the local cpu (unlike with preempt disabled),
 * but they don't need to be atomic with respect to other cpus like in
 * true SMP (so they need either to either locally disable irq around
 * the read or for example on x86 they can be still implemented as a
 * cmpxchg8b without the need of the lock prefix). For SMP compiles
 * and 64bit archs it makes no difference if preempt is enabled or not.
 */



static inline loff_t i_size_read(const struct inode *inode)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
	loff_t i_size;
	unsigned int seq;

	do {
		seq = read_seqcount_begin(&inode->i_size_seqcount);
		i_size = inode->i_size;
	} while (read_seqcount_retry(&inode->i_size_seqcount, seq));
	return i_size;
#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
	loff_t i_size;

	preempt_disable();
	i_size = inode->i_size;
	preempt_enable();
	return i_size;
#else
	return inode->i_size;
#endif
}


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/*
 * NOTE: unlike i_size_read(), i_size_write() does need locking around it
 * (normally i_mutex), otherwise on 32bit/SMP an update of i_size_seqcount
 * can be lost, resulting in subsequent i_size_read() calls spinning forever.
 */



static inline void i_size_write(struct inode *inode, loff_t i_size)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
	preempt_disable();
	write_seqcount_begin(&inode->i_size_seqcount);
	inode->i_size = i_size;
	write_seqcount_end(&inode->i_size_seqcount);
	preempt_enable();
#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
	preempt_disable();
	inode->i_size = i_size;
	preempt_enable();
#else
	inode->i_size = i_size;
#endif
}


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static inline unsigned iminor(const struct inode *inode)
{
	return MINOR(inode->i_rdev);
}


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static inline unsigned imajor(const struct inode *inode)
{
	return MAJOR(inode->i_rdev);
}


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extern struct block_device *I_BDEV(struct inode *inode);


struct fown_struct {
	
rwlock_t lock;          /* protects pid, uid, euid fields */
	
struct pid *pid;	/* pid or -pgrp where SIGIO should be sent */
	
enum pid_type pid_type;	/* Kind of process group SIGIO should be sent to */
	

kuid_t uid, euid;	/* uid/euid of process setting the owner */
	
int signum;		/* posix.1b rt signal to be delivered on IO */
};

/*
 * Track a single file's readahead state
 */

struct file_ra_state {
	
pgoff_t start;			/* where readahead started */
	
unsigned int size;		/* # of readahead pages */
	
unsigned int async_size;	/* do asynchronous readahead when
                                           there are only # of pages ahead */

	
unsigned int ra_pages;		/* Maximum readahead window */