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linux/fs/sysv/sysv.h
David Howells a528d35e8b statx: Add a system call to make enhanced file info available 
Add a system call to make extended file information available, including
file creation and some attribute flags where available through the
underlying filesystem.

The getattr inode operation is altered to take two additional arguments: a
u32 request_mask and an unsigned int flags that indicate the
synchronisation mode.  This change is propagated to the vfs_getattr*()
function.

Functions like vfs_stat() are now inline wrappers around new functions
vfs_statx() and vfs_statx_fd() to reduce stack usage.

========
OVERVIEW
========

The idea was initially proposed as a set of xattrs that could be retrieved
with getxattr(), but the general preference proved to be for a new syscall
with an extended stat structure.

A number of requests were gathered for features to be included.  The
following have been included:

 (1) Make the fields a consistent size on all arches and make them large.

 (2) Spare space, request flags and information flags are provided for
     future expansion.

 (3) Better support for the y2038 problem [Arnd Bergmann] (tv_sec is an
     __s64).

 (4) Creation time: The SMB protocol carries the creation time, which could
     be exported by Samba, which will in turn help CIFS make use of
     FS-Cache as that can be used for coherency data (stx_btime).

     This is also specified in NFSv4 as a recommended attribute and could
     be exported by NFSD [Steve French].

 (5) Lightweight stat: Ask for just those details of interest, and allow a
     netfs (such as NFS) to approximate anything not of interest, possibly
     without going to the server [Trond Myklebust, Ulrich Drepper, Andreas
     Dilger] (AT_STATX_DONT_SYNC).

 (6) Heavyweight stat: Force a netfs to go to the server, even if it thinks
     its cached attributes are up to date [Trond Myklebust]
     (AT_STATX_FORCE_SYNC).

And the following have been left out for future extension:

 (7) Data version number: Could be used by userspace NFS servers [Aneesh
     Kumar].

     Can also be used to modify fill_post_wcc() in NFSD which retrieves
     i_version directly, but has just called vfs_getattr().  It could get
     it from the kstat struct if it used vfs_xgetattr() instead.

     (There's disagreement on the exact semantics of a single field, since
     not all filesystems do this the same way).

 (8) BSD stat compatibility: Including more fields from the BSD stat such
     as creation time (st_btime) and inode generation number (st_gen)
     [Jeremy Allison, Bernd Schubert].

 (9) Inode generation number: Useful for FUSE and userspace NFS servers
     [Bernd Schubert].

     (This was asked for but later deemed unnecessary with the
     open-by-handle capability available and caused disagreement as to
     whether it's a security hole or not).

(10) Extra coherency data may be useful in making backups [Andreas Dilger].

     (No particular data were offered, but things like last backup
     timestamp, the data version number and the DOS archive bit would come
     into this category).

(11) Allow the filesystem to indicate what it can/cannot provide: A
     filesystem can now say it doesn't support a standard stat feature if
     that isn't available, so if, for instance, inode numbers or UIDs don't
     exist or are fabricated locally...

     (This requires a separate system call - I have an fsinfo() call idea
     for this).

(12) Store a 16-byte volume ID in the superblock that can be returned in
     struct xstat [Steve French].

     (Deferred to fsinfo).

(13) Include granularity fields in the time data to indicate the
     granularity of each of the times (NFSv4 time_delta) [Steve French].

     (Deferred to fsinfo).

(14) FS_IOC_GETFLAGS value.  These could be translated to BSD's st_flags.
     Note that the Linux IOC flags are a mess and filesystems such as Ext4
     define flags that aren't in linux/fs.h, so translation in the kernel
     may be a necessity (or, possibly, we provide the filesystem type too).

     (Some attributes are made available in stx_attributes, but the general
     feeling was that the IOC flags were to ext[234]-specific and shouldn't
     be exposed through statx this way).

(15) Mask of features available on file (eg: ACLs, seclabel) [Brad Boyer,
     Michael Kerrisk].

     (Deferred, probably to fsinfo.  Finding out if there's an ACL or
     seclabal might require extra filesystem operations).

(16) Femtosecond-resolution timestamps [Dave Chinner].

     (A __reserved field has been left in the statx_timestamp struct for
     this - if there proves to be a need).

(17) A set multiple attributes syscall to go with this.

===============
NEW SYSTEM CALL
===============

The new system call is:

	int ret = statx(int dfd,
			const char *filename,
			unsigned int flags,
			unsigned int mask,
			struct statx *buffer);

The dfd, filename and flags parameters indicate the file to query, in a
similar way to fstatat().  There is no equivalent of lstat() as that can be
emulated with statx() by passing AT_SYMLINK_NOFOLLOW in flags.  There is
also no equivalent of fstat() as that can be emulated by passing a NULL
filename to statx() with the fd of interest in dfd.

Whether or not statx() synchronises the attributes with the backing store
can be controlled by OR'ing a value into the flags argument (this typically
only affects network filesystems):

 (1) AT_STATX_SYNC_AS_STAT tells statx() to behave as stat() does in this
     respect.

 (2) AT_STATX_FORCE_SYNC will require a network filesystem to synchronise
     its attributes with the server - which might require data writeback to
     occur to get the timestamps correct.

 (3) AT_STATX_DONT_SYNC will suppress synchronisation with the server in a
     network filesystem.  The resulting values should be considered
     approximate.

mask is a bitmask indicating the fields in struct statx that are of
interest to the caller.  The user should set this to STATX_BASIC_STATS to
get the basic set returned by stat().  It should be noted that asking for
more information may entail extra I/O operations.

buffer points to the destination for the data.  This must be 256 bytes in
size.

======================
MAIN ATTRIBUTES RECORD
======================

The following structures are defined in which to return the main attribute
set:

	struct statx_timestamp {
		__s64	tv_sec;
		__s32	tv_nsec;
		__s32	__reserved;
	};

	struct statx {
		__u32	stx_mask;
		__u32	stx_blksize;
		__u64	stx_attributes;
		__u32	stx_nlink;
		__u32	stx_uid;
		__u32	stx_gid;
		__u16	stx_mode;
		__u16	__spare0[1];
		__u64	stx_ino;
		__u64	stx_size;
		__u64	stx_blocks;
		__u64	__spare1[1];
		struct statx_timestamp	stx_atime;
		struct statx_timestamp	stx_btime;
		struct statx_timestamp	stx_ctime;
		struct statx_timestamp	stx_mtime;
		__u32	stx_rdev_major;
		__u32	stx_rdev_minor;
		__u32	stx_dev_major;
		__u32	stx_dev_minor;
		__u64	__spare2[14];
	};

The defined bits in request_mask and stx_mask are:

	STATX_TYPE		Want/got stx_mode & S_IFMT
	STATX_MODE		Want/got stx_mode & ~S_IFMT
	STATX_NLINK		Want/got stx_nlink
	STATX_UID		Want/got stx_uid
	STATX_GID		Want/got stx_gid
	STATX_ATIME		Want/got stx_atime{,_ns}
	STATX_MTIME		Want/got stx_mtime{,_ns}
	STATX_CTIME		Want/got stx_ctime{,_ns}
	STATX_INO		Want/got stx_ino
	STATX_SIZE		Want/got stx_size
	STATX_BLOCKS		Want/got stx_blocks
	STATX_BASIC_STATS	[The stuff in the normal stat struct]
	STATX_BTIME		Want/got stx_btime{,_ns}
	STATX_ALL		[All currently available stuff]

stx_btime is the file creation time, stx_mask is a bitmask indicating the
data provided and __spares*[] are where as-yet undefined fields can be
placed.

Time fields are structures with separate seconds and nanoseconds fields
plus a reserved field in case we want to add even finer resolution.  Note
that times will be negative if before 1970; in such a case, the nanosecond
fields will also be negative if not zero.

The bits defined in the stx_attributes field convey information about a
file, how it is accessed, where it is and what it does.  The following
attributes map to FS_*_FL flags and are the same numerical value:

	STATX_ATTR_COMPRESSED		File is compressed by the fs
	STATX_ATTR_IMMUTABLE		File is marked immutable
	STATX_ATTR_APPEND		File is append-only
	STATX_ATTR_NODUMP		File is not to be dumped
	STATX_ATTR_ENCRYPTED		File requires key to decrypt in fs

Within the kernel, the supported flags are listed by:

	KSTAT_ATTR_FS_IOC_FLAGS

[Are any other IOC flags of sufficient general interest to be exposed
through this interface?]

New flags include:

	STATX_ATTR_AUTOMOUNT		Object is an automount trigger

These are for the use of GUI tools that might want to mark files specially,
depending on what they are.

Fields in struct statx come in a number of classes:

 (0) stx_dev_*, stx_blksize.

     These are local system information and are always available.

 (1) stx_mode, stx_nlinks, stx_uid, stx_gid, stx_[amc]time, stx_ino,
     stx_size, stx_blocks.

     These will be returned whether the caller asks for them or not.  The
     corresponding bits in stx_mask will be set to indicate whether they
     actually have valid values.

     If the caller didn't ask for them, then they may be approximated.  For
     example, NFS won't waste any time updating them from the server,
     unless as a byproduct of updating something requested.

     If the values don't actually exist for the underlying object (such as
     UID or GID on a DOS file), then the bit won't be set in the stx_mask,
     even if the caller asked for the value.  In such a case, the returned
     value will be a fabrication.

     Note that there are instances where the type might not be valid, for
     instance Windows reparse points.

 (2) stx_rdev_*.

     This will be set only if stx_mode indicates we're looking at a
     blockdev or a chardev, otherwise will be 0.

 (3) stx_btime.

     Similar to (1), except this will be set to 0 if it doesn't exist.

=======
TESTING
=======

The following test program can be used to test the statx system call:

	samples/statx/test-statx.c

Just compile and run, passing it paths to the files you want to examine.
The file is built automatically if CONFIG_SAMPLES is enabled.

Here's some example output.  Firstly, an NFS directory that crosses to
another FSID.  Note that the AUTOMOUNT attribute is set because transiting
this directory will cause d_automount to be invoked by the VFS.

	[root@andromeda ~]# /tmp/test-statx -A /warthog/data
	statx(/warthog/data) = 0
	results=7ff
	  Size: 4096            Blocks: 8          IO Block: 1048576  directory
	Device: 00:26           Inode: 1703937     Links: 125
	Access: (3777/drwxrwxrwx)  Uid:     0   Gid:  4041
	Access: 2016-11-24 09:02:12.219699527+0000
	Modify: 2016-11-17 10:44:36.225653653+0000
	Change: 2016-11-17 10:44:36.225653653+0000
	Attributes: 0000000000001000 (-------- -------- -------- -------- -------- -------- ---m---- --------)

Secondly, the result of automounting on that directory.

	[root@andromeda ~]# /tmp/test-statx /warthog/data
	statx(/warthog/data) = 0
	results=7ff
	  Size: 4096            Blocks: 8          IO Block: 1048576  directory
	Device: 00:27           Inode: 2           Links: 125
	Access: (3777/drwxrwxrwx)  Uid:     0   Gid:  4041
	Access: 2016-11-24 09:02:12.219699527+0000
	Modify: 2016-11-17 10:44:36.225653653+0000
	Change: 2016-11-17 10:44:36.225653653+0000

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-03-02 20:51:15 -05:00

247 lines
7.7 KiB
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#ifndef _SYSV_H
#define _SYSV_H
#include <linux/buffer_head.h>
typedef __u16 __bitwise __fs16;
typedef __u32 __bitwise __fs32;
#include <linux/sysv_fs.h>
/*
* SystemV/V7/Coherent super-block data in memory
*
* The SystemV/V7/Coherent superblock contains dynamic data (it gets modified
* while the system is running). This is in contrast to the Minix and Berkeley
* filesystems (where the superblock is never modified). This affects the
* sync() operation: we must keep the superblock in a disk buffer and use this
* one as our "working copy".
*/
struct sysv_sb_info {
struct super_block *s_sb; /* VFS superblock */
int s_type; /* file system type: FSTYPE_{XENIX|SYSV|COH} */
char s_bytesex; /* bytesex (le/be/pdp) */
char s_truncate; /* if 1: names > SYSV_NAMELEN chars are truncated */
/* if 0: they are disallowed (ENAMETOOLONG) */
unsigned int s_inodes_per_block; /* number of inodes per block */
unsigned int s_inodes_per_block_1; /* inodes_per_block - 1 */
unsigned int s_inodes_per_block_bits; /* log2(inodes_per_block) */
unsigned int s_ind_per_block; /* number of indirections per block */
unsigned int s_ind_per_block_bits; /* log2(ind_per_block) */
unsigned int s_ind_per_block_2; /* ind_per_block ^ 2 */
unsigned int s_toobig_block; /* 10 + ipb + ipb^2 + ipb^3 */
unsigned int s_block_base; /* physical block number of block 0 */
unsigned short s_fic_size; /* free inode cache size, NICINOD */
unsigned short s_flc_size; /* free block list chunk size, NICFREE */
/* The superblock is kept in one or two disk buffers: */
struct buffer_head *s_bh1;
struct buffer_head *s_bh2;
/* These are pointers into the disk buffer, to compensate for
different superblock layout. */
char * s_sbd1; /* entire superblock data, for part 1 */
char * s_sbd2; /* entire superblock data, for part 2 */
__fs16 *s_sb_fic_count; /* pointer to s_sbd->s_ninode */
sysv_ino_t *s_sb_fic_inodes; /* pointer to s_sbd->s_inode */
__fs16 *s_sb_total_free_inodes; /* pointer to s_sbd->s_tinode */
__fs16 *s_bcache_count; /* pointer to s_sbd->s_nfree */
sysv_zone_t *s_bcache; /* pointer to s_sbd->s_free */
__fs32 *s_free_blocks; /* pointer to s_sbd->s_tfree */
__fs32 *s_sb_time; /* pointer to s_sbd->s_time */
__fs32 *s_sb_state; /* pointer to s_sbd->s_state, only FSTYPE_SYSV */
/* We keep those superblock entities that don't change here;
this saves us an indirection and perhaps a conversion. */
u32 s_firstinodezone; /* index of first inode zone */
u32 s_firstdatazone; /* same as s_sbd->s_isize */
u32 s_ninodes; /* total number of inodes */
u32 s_ndatazones; /* total number of data zones */
u32 s_nzones; /* same as s_sbd->s_fsize */
u16 s_namelen; /* max length of dir entry */
int s_forced_ro;
struct mutex s_lock;
};
/*
* SystemV/V7/Coherent FS inode data in memory
*/
struct sysv_inode_info {
__fs32 i_data[13];
u32 i_dir_start_lookup;
struct inode vfs_inode;
};
static inline struct sysv_inode_info *SYSV_I(struct inode *inode)
{
return container_of(inode, struct sysv_inode_info, vfs_inode);
}
static inline struct sysv_sb_info *SYSV_SB(struct super_block *sb)
{
return sb->s_fs_info;
}
/* identify the FS in memory */
enum {
FSTYPE_NONE = 0,
FSTYPE_XENIX,
FSTYPE_SYSV4,
FSTYPE_SYSV2,
FSTYPE_COH,
FSTYPE_V7,
FSTYPE_AFS,
FSTYPE_END,
};
#define SYSV_MAGIC_BASE 0x012FF7B3
#define XENIX_SUPER_MAGIC (SYSV_MAGIC_BASE+FSTYPE_XENIX)
#define SYSV4_SUPER_MAGIC (SYSV_MAGIC_BASE+FSTYPE_SYSV4)
#define SYSV2_SUPER_MAGIC (SYSV_MAGIC_BASE+FSTYPE_SYSV2)
#define COH_SUPER_MAGIC (SYSV_MAGIC_BASE+FSTYPE_COH)
/* Admissible values for i_nlink: 0.._LINK_MAX */
enum {
XENIX_LINK_MAX = 126, /* ?? */
SYSV_LINK_MAX = 126, /* 127? 251? */
V7_LINK_MAX = 126, /* ?? */
COH_LINK_MAX = 10000,
};
static inline void dirty_sb(struct super_block *sb)
{
struct sysv_sb_info *sbi = SYSV_SB(sb);
mark_buffer_dirty(sbi->s_bh1);
if (sbi->s_bh1 != sbi->s_bh2)
mark_buffer_dirty(sbi->s_bh2);
}
/* ialloc.c */
extern struct sysv_inode *sysv_raw_inode(struct super_block *, unsigned,
struct buffer_head **);
extern struct inode * sysv_new_inode(const struct inode *, umode_t);
extern void sysv_free_inode(struct inode *);
extern unsigned long sysv_count_free_inodes(struct super_block *);
/* balloc.c */
extern sysv_zone_t sysv_new_block(struct super_block *);
extern void sysv_free_block(struct super_block *, sysv_zone_t);
extern unsigned long sysv_count_free_blocks(struct super_block *);
/* itree.c */
extern void sysv_truncate(struct inode *);
extern int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len);
/* inode.c */
extern struct inode *sysv_iget(struct super_block *, unsigned int);
extern int sysv_write_inode(struct inode *, struct writeback_control *wbc);
extern int sysv_sync_inode(struct inode *);
extern void sysv_set_inode(struct inode *, dev_t);
extern int sysv_getattr(const struct path *, struct kstat *, u32, unsigned int);
extern int sysv_init_icache(void);
extern void sysv_destroy_icache(void);
/* dir.c */
extern struct sysv_dir_entry *sysv_find_entry(struct dentry *, struct page **);
extern int sysv_add_link(struct dentry *, struct inode *);
extern int sysv_delete_entry(struct sysv_dir_entry *, struct page *);
extern int sysv_make_empty(struct inode *, struct inode *);
extern int sysv_empty_dir(struct inode *);
extern void sysv_set_link(struct sysv_dir_entry *, struct page *,
struct inode *);
extern struct sysv_dir_entry *sysv_dotdot(struct inode *, struct page **);
extern ino_t sysv_inode_by_name(struct dentry *);
extern const struct inode_operations sysv_file_inode_operations;
extern const struct inode_operations sysv_dir_inode_operations;
extern const struct file_operations sysv_file_operations;
extern const struct file_operations sysv_dir_operations;
extern const struct address_space_operations sysv_aops;
extern const struct super_operations sysv_sops;
extern const struct dentry_operations sysv_dentry_operations;
enum {
BYTESEX_LE,
BYTESEX_PDP,
BYTESEX_BE,
};
static inline u32 PDP_swab(u32 x)
{
#ifdef __LITTLE_ENDIAN
return ((x & 0xffff) << 16) | ((x & 0xffff0000) >> 16);
#else
#ifdef __BIG_ENDIAN
return ((x & 0xff00ff) << 8) | ((x & 0xff00ff00) >> 8);
#else
#error BYTESEX
#endif
#endif
}
static inline __u32 fs32_to_cpu(struct sysv_sb_info *sbi, __fs32 n)
{
if (sbi->s_bytesex == BYTESEX_PDP)
return PDP_swab((__force __u32)n);
else if (sbi->s_bytesex == BYTESEX_LE)
return le32_to_cpu((__force __le32)n);
else
return be32_to_cpu((__force __be32)n);
}
static inline __fs32 cpu_to_fs32(struct sysv_sb_info *sbi, __u32 n)
{
if (sbi->s_bytesex == BYTESEX_PDP)
return (__force __fs32)PDP_swab(n);
else if (sbi->s_bytesex == BYTESEX_LE)
return (__force __fs32)cpu_to_le32(n);
else
return (__force __fs32)cpu_to_be32(n);
}
static inline __fs32 fs32_add(struct sysv_sb_info *sbi, __fs32 *n, int d)
{
if (sbi->s_bytesex == BYTESEX_PDP)
*(__u32*)n = PDP_swab(PDP_swab(*(__u32*)n)+d);
else if (sbi->s_bytesex == BYTESEX_LE)
le32_add_cpu((__le32 *)n, d);
else
be32_add_cpu((__be32 *)n, d);
return *n;
}
static inline __u16 fs16_to_cpu(struct sysv_sb_info *sbi, __fs16 n)
{
if (sbi->s_bytesex != BYTESEX_BE)
return le16_to_cpu((__force __le16)n);
else
return be16_to_cpu((__force __be16)n);
}
static inline __fs16 cpu_to_fs16(struct sysv_sb_info *sbi, __u16 n)
{
if (sbi->s_bytesex != BYTESEX_BE)
return (__force __fs16)cpu_to_le16(n);
else
return (__force __fs16)cpu_to_be16(n);
}
static inline __fs16 fs16_add(struct sysv_sb_info *sbi, __fs16 *n, int d)
{
if (sbi->s_bytesex != BYTESEX_BE)
le16_add_cpu((__le16 *)n, d);
else
be16_add_cpu((__be16 *)n, d);
return *n;
}
#endif /* _SYSV_H */
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