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28b2013587
linux/fs/minix/minix.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

170 lines
5.2 KiB
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#ifndef FS_MINIX_H
#define FS_MINIX_H
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/minix_fs.h>
#define INODE_VERSION(inode) minix_sb(inode->i_sb)->s_version
#define MINIX_V1 0x0001 /* original minix fs */
#define MINIX_V2 0x0002 /* minix V2 fs */
#define MINIX_V3 0x0003 /* minix V3 fs */
/*
* minix fs inode data in memory
*/
struct minix_inode_info {
union {
__u16 i1_data[16];
__u32 i2_data[16];
} u;
struct inode vfs_inode;
};
/*
* minix super-block data in memory
*/
struct minix_sb_info {
unsigned long s_ninodes;
unsigned long s_nzones;
unsigned long s_imap_blocks;
unsigned long s_zmap_blocks;
unsigned long s_firstdatazone;
unsigned long s_log_zone_size;
unsigned long s_max_size;
int s_dirsize;
int s_namelen;
struct buffer_head ** s_imap;
struct buffer_head ** s_zmap;
struct buffer_head * s_sbh;
struct minix_super_block * s_ms;
unsigned short s_mount_state;
unsigned short s_version;
};
extern struct inode *minix_iget(struct super_block *, unsigned long);
extern struct minix_inode * minix_V1_raw_inode(struct super_block *, ino_t, struct buffer_head **);
extern struct minix2_inode * minix_V2_raw_inode(struct super_block *, ino_t, struct buffer_head **);
extern struct inode * minix_new_inode(const struct inode *, umode_t, int *);
extern void minix_free_inode(struct inode * inode);
extern unsigned long minix_count_free_inodes(struct super_block *sb);
extern int minix_new_block(struct inode * inode);
extern void minix_free_block(struct inode *inode, unsigned long block);
extern unsigned long minix_count_free_blocks(struct super_block *sb);
extern int minix_getattr(const struct path *, struct kstat *, u32, unsigned int);
extern int minix_prepare_chunk(struct page *page, loff_t pos, unsigned len);
extern void V1_minix_truncate(struct inode *);
extern void V2_minix_truncate(struct inode *);
extern void minix_truncate(struct inode *);
extern void minix_set_inode(struct inode *, dev_t);
extern int V1_minix_get_block(struct inode *, long, struct buffer_head *, int);
extern int V2_minix_get_block(struct inode *, long, struct buffer_head *, int);
extern unsigned V1_minix_blocks(loff_t, struct super_block *);
extern unsigned V2_minix_blocks(loff_t, struct super_block *);
extern struct minix_dir_entry *minix_find_entry(struct dentry*, struct page**);
extern int minix_add_link(struct dentry*, struct inode*);
extern int minix_delete_entry(struct minix_dir_entry*, struct page*);
extern int minix_make_empty(struct inode*, struct inode*);
extern int minix_empty_dir(struct inode*);
extern void minix_set_link(struct minix_dir_entry*, struct page*, struct inode*);
extern struct minix_dir_entry *minix_dotdot(struct inode*, struct page**);
extern ino_t minix_inode_by_name(struct dentry*);
extern const struct inode_operations minix_file_inode_operations;
extern const struct inode_operations minix_dir_inode_operations;
extern const struct file_operations minix_file_operations;
extern const struct file_operations minix_dir_operations;
static inline struct minix_sb_info *minix_sb(struct super_block *sb)
{
return sb->s_fs_info;
}
static inline struct minix_inode_info *minix_i(struct inode *inode)
{
return container_of(inode, struct minix_inode_info, vfs_inode);
}
static inline unsigned minix_blocks_needed(unsigned bits, unsigned blocksize)
{
return DIV_ROUND_UP(bits, blocksize * 8);
}
#if defined(CONFIG_MINIX_FS_NATIVE_ENDIAN) && \
defined(CONFIG_MINIX_FS_BIG_ENDIAN_16BIT_INDEXED)
#error Minix file system byte order broken
#elif defined(CONFIG_MINIX_FS_NATIVE_ENDIAN)
/*
* big-endian 32 or 64 bit indexed bitmaps on big-endian system or
* little-endian bitmaps on little-endian system
*/
#define minix_test_and_set_bit(nr, addr) \
__test_and_set_bit((nr), (unsigned long *)(addr))
#define minix_set_bit(nr, addr) \
__set_bit((nr), (unsigned long *)(addr))
#define minix_test_and_clear_bit(nr, addr) \
__test_and_clear_bit((nr), (unsigned long *)(addr))
#define minix_test_bit(nr, addr) \
test_bit((nr), (unsigned long *)(addr))
#define minix_find_first_zero_bit(addr, size) \
find_first_zero_bit((unsigned long *)(addr), (size))
#elif defined(CONFIG_MINIX_FS_BIG_ENDIAN_16BIT_INDEXED)
/*
* big-endian 16bit indexed bitmaps
*/
static inline int minix_find_first_zero_bit(const void *vaddr, unsigned size)
{
const unsigned short *p = vaddr, *addr = vaddr;
unsigned short num;
if (!size)
return 0;
size >>= 4;
while (*p++ == 0xffff) {
if (--size == 0)
return (p - addr) << 4;
}
num = *--p;
return ((p - addr) << 4) + ffz(num);
}
#define minix_test_and_set_bit(nr, addr) \
__test_and_set_bit((nr) ^ 16, (unsigned long *)(addr))
#define minix_set_bit(nr, addr) \
__set_bit((nr) ^ 16, (unsigned long *)(addr))
#define minix_test_and_clear_bit(nr, addr) \
__test_and_clear_bit((nr) ^ 16, (unsigned long *)(addr))
static inline int minix_test_bit(int nr, const void *vaddr)
{
const unsigned short *p = vaddr;
return (p[nr >> 4] & (1U << (nr & 15))) != 0;
}
#else
/*
* little-endian bitmaps
*/
#define minix_test_and_set_bit __test_and_set_bit_le
#define minix_set_bit __set_bit_le
#define minix_test_and_clear_bit __test_and_clear_bit_le
#define minix_test_bit test_bit_le
#define minix_find_first_zero_bit find_first_zero_bit_le
#endif
#endif /* FS_MINIX_H */
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