[PATCH 1/6] statx: Add a system call to make enhanced file info available

David Howells
2016-04-29T12:57:43Z

Add a system call to make extended file information available, including
file creation time, inode version and data version where available through
the underlying filesystem.

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

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

This has a number of uses:

(1) Better support for the y2038 problem [Arnd Bergmann].

(2) 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.

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

(3) 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].

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

(5) 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.

(6) 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].

(7) 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

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

(9) 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...

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

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

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

(13) 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).

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

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

Note that not all of the above are implemented here.

===============
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. 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.

AT_FORCE_ATTR_SYNC can be set in flags. This will require a network
filesystem to synchronise its attributes with the server.

AT_NO_ATTR_SYNC can be set in flags. This 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().

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 {
__u32 st_mask;
__u32 st_information;
__u32 st_blksize;
__u32 st_nlink;
__u32 st_gen;
__u32 st_uid;
__u32 st_gid;
__u16 st_mode;
__u16 __spare0[1];
__u64 st_ino;
__u64 st_size;
__u64 st_blocks;
__u64 st_version;
__s64 st_atime;
__s64 st_btime;
__s64 st_ctime;
__s64 st_mtime;
__s32 st_atime_ns;
__s32 st_btime_ns;
__s32 st_ctime_ns;
__s32 st_mtime_ns;
__u32 st_rdev_major;
__u32 st_rdev_minor;
__u32 st_dev_major;
__u32 st_dev_minor;
__u64 __spare1[16];
};

where st_information is local system information about the file, st_gen is
the inode generation number, st_btime is the file creation time, st_version
is the data version number (i_version), st_mask is a bitmask indicating the
data provided and __spares*[] are where as-yet undefined fields can be
placed.

Time fields are split into separate seconds and nanoseconds fields to make
packing easier and the granularities can be queried with the filesystem
info system call. Note that times will be negative if before 1970; in such
a case, the nanosecond fields should also be negative if not zero.

The defined bits in request_mask and st_mask are:

STATX_MODE Want/got st_mode
STATX_NLINK Want/got st_nlink
STATX_UID Want/got st_uid
STATX_GID Want/got st_gid
STATX_RDEV Want/got st_rdev_*
STATX_ATIME Want/got st_atime
STATX_MTIME Want/got st_mtime
STATX_CTIME Want/got st_ctime
STATX_INO Want/got st_ino
STATX_SIZE Want/got st_size
STATX_BLOCKS Want/got st_blocks
STATX_BASIC_STATS [The stuff in the normal stat struct]
STATX_BTIME Want/got st_btime
STATX_VERSION Want/got st_data_version
STATX_GEN Want/got st_gen
STATX_ALL_STATS [All currently available stuff]

The defined bits in the st_information field give local system data on a
file, how it is accessed, where it is and what it does:

STATX_INFO_ENCRYPTED File is encrypted
STATX_INFO_TEMPORARY File is temporary
STATX_INFO_FABRICATED File was made up by filesystem
STATX_INFO_KERNEL_API File is kernel API (eg: procfs/sysfs)
STATX_INFO_REMOTE File is remote
STATX_INFO_AUTOMOUNT Dir is automount trigger
STATX_INFO_AUTODIR Dir provides unlisted automounts
STATX_INFO_NONSYSTEM_OWNERSHIP File has non-system ownership details

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) st_information, st_dev_*, st_blksize.

These are local data and are always available.

(1) st_nlinks, st_uid, st_gid, st_[amc]time*, st_ino, st_size, st_blocks.

These will be returned whether the caller asks for them or not. The
corresponding bits in st_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 st_mask,
even if the caller asked for the value. In such a case, the returned
value will be a fabrication.

(2) st_mode.

The part of this that identifies the file type will always be
available, irrespective of the setting of STATX_MODE. The access
flags and sticky bit are as for class (1).

(3) st_rdev_*.

As for class (1), but this will be cleared if the file is not a
blockdev or chardev. The bit will be cleared if the value is not
returned.

(4) File creation time (st_btime*), data version (st_version), inode
generation number (st_gen).

These will be returned if available whether the caller asked for them or
not. The corresponding bits in st_mask will be set or cleared as
appropriate to indicate a valid value.

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.

=======
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 FABRICATED and AUTOMOUNT info flags are set.
The former because the directory is invented locally as we don't see the
underlying dir on the server, the latter because transiting this directory
will cause d_automount to be invoked by the VFS.

[root@andromeda tmp]# ./samples/statx/test-statx -A /warthog/data
statx(/warthog/data) = 0
results=4fef
Size: 4096 Blocks: 8 IO Block: 1048576 directory
Device: 00:1d Inode: 2 Links: 110
Access: (3777/drwxrwxrwx) Uid: -2
Gid: 4294967294
Access: 2012-04-30 09:01:55.283819565+0100
Modify: 2012-03-28 19:01:19.405465361+0100
Change: 2012-03-28 19:01:19.405465361+0100
Data version: ef51734f11e92a18h
Information: 00000134 (-------- -------- -------a --mr-f--)

Secondly, the result of automounting on that directory.

[root@andromeda tmp]# ./samples/statx/test-statx /warthog/data
statx(/warthog/data) = 0
results=14fef
Size: 4096 Blocks: 8 IO Block: 1048576 directory
Device: 00:1e Inode: 2 Links: 110
Access: (3777/drwxrwxrwx) Uid: -2
Gid: 4294967294
Access: 2012-04-30 09:01:55.283819565+0100
Modify: 2012-03-28 19:01:19.405465361+0100
Change: 2012-03-28 19:01:19.405465361+0100
Data version: ef51734f11e92a18h
Information: 00000110 (-------- -------- -------a ---r----)

Signed-off-by: David Howells <dhowells@redhat.com>
---

arch/x86/entry/syscalls/syscall_32.tbl | 1
arch/x86/entry/syscalls/syscall_64.tbl | 1
fs/exportfs/expfs.c | 4
fs/stat.c | 303 +++++++++++++++++++++++++++++---
include/linux/fs.h | 5 -
include/linux/stat.h | 15 +-
include/linux/syscalls.h | 4
include/uapi/linux/fcntl.h | 2
include/uapi/linux/stat.h | 109 ++++++++++++
samples/Makefile | 2
samples/statx/Makefile | 10 +
samples/statx/test-statx.c | 243 ++++++++++++++++++++++++++
12 files changed, 662 insertions(+), 37 deletions(-)
create mode 100644 samples/statx/Makefile
create mode 100644 samples/statx/test-statx.c

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index b30dd8154cc2..b99a6b3a167c 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -386,3 +386,4 @@
377 i386 copy_file_range sys_copy_file_range
378 i386 preadv2 sys_preadv2
379 i386 pwritev2 sys_pwritev2
+380 i386 statx sys_statx
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index cac6d17ce5db..6d5ef6c87cdc 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -335,6 +335,7 @@
326 common copy_file_range sys_copy_file_range
327 64 preadv2 sys_preadv2
328 64 pwritev2 sys_pwritev2
+329 common statx sys_statx

#
# x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index c46f1a190b8d..cd6d9cbc9300 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -295,7 +295,9 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
* filesystem supports 64-bit inode numbers. So we need to
* actually call ->getattr, not just read i_ino:
*/
- error = vfs_getattr_nosec(&child_path, &stat);
+ stat.query_flags = 0;
+ stat.request_mask = STATX_BASIC_STATS;
+ error = vfs_xgetattr_nosec(&child_path, &stat);
if (error)
return error;
buffer.ino = stat.ino;
diff --git a/fs/stat.c b/fs/stat.c
index bc045c7994e1..c2f8370dab13 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -18,6 +18,15 @@
#include <asm/uaccess.h>
#include <asm/unistd.h>

+/**
+ * generic_fillattr - Fill in the basic attributes from the inode struct
+ * @inode: Inode to use as the source
+ * @stat: Where to fill in the attributes
+ *
+ * Fill in the basic attributes in the kstat structure from data that's to be
+ * found on the VFS inode structure. This is the default if no getattr inode
+ * operation is supplied.
+ */
void generic_fillattr(struct inode *inode, struct kstat *stat)
{
stat->dev = inode->i_sb->s_dev;
@@ -27,87 +36,197 @@ void generic_fillattr(struct inode *inode, struct kstat *stat)
stat->uid = inode->i_uid;
stat->gid = inode->i_gid;
stat->rdev = inode->i_rdev;
- stat->size = i_size_read(inode);
- stat->atime = inode->i_atime;
stat->mtime = inode->i_mtime;
stat->ctime = inode->i_ctime;
- stat->blksize = (1 << inode->i_blkbits);
+ stat->size = i_size_read(inode);
stat->blocks = inode->i_blocks;
-}
+ stat->blksize = 1 << inode->i_blkbits;

+ stat->result_mask |= STATX_BASIC_STATS & ~STATX_RDEV;
+ if (IS_NOATIME(inode))
+ stat->result_mask &= ~STATX_ATIME;
+ else
+ stat->atime = inode->i_atime;
+
+ if (S_ISREG(stat->mode) && stat->nlink == 0)
+ stat->information |= STATX_INFO_TEMPORARY;
+ if (IS_AUTOMOUNT(inode))
+ stat->information |= STATX_INFO_AUTOMOUNT;
+
+ if (unlikely(S_ISBLK(stat->mode) || S_ISCHR(stat->mode)))
+ stat->result_mask |= STATX_RDEV;
+}
EXPORT_SYMBOL(generic_fillattr);

/**
- * vfs_getattr_nosec - getattr without security checks
+ * vfs_xgetattr_nosec - getattr without security checks
* @path: file to get attributes from
* @stat: structure to return attributes in
*
* Get attributes without calling security_inode_getattr.
*
- * Currently the only caller other than vfs_getattr is internal to the
- * filehandle lookup code, which uses only the inode number and returns
- * no attributes to any user. Any other code probably wants
- * vfs_getattr.
+ * Currently the only caller other than vfs_xgetattr is internal to the
+ * filehandle lookup code, which uses only the inode number and returns no
+ * attributes to any user. Any other code probably wants vfs_xgetattr.
+ *
+ * The caller must set stat->request_mask to indicate what they want and
+ * stat->query_flags to indicate whether the server should be queried.
*/
-int vfs_getattr_nosec(struct path *path, struct kstat *stat)
+int vfs_xgetattr_nosec(struct path *path, struct kstat *stat)
{
struct inode *inode = d_backing_inode(path->dentry);

+ stat->query_flags &= ~KSTAT_QUERY_FLAGS;
+ if ((stat->query_flags & AT_FORCE_ATTR_SYNC) &&
+ (stat->query_flags & AT_NO_ATTR_SYNC))
+ return -EINVAL;
+
+ stat->result_mask = 0;
+ stat->information = 0;
if (inode->i_op->getattr)
return inode->i_op->getattr(path->mnt, path->dentry, stat);

generic_fillattr(inode, stat);
return 0;
}
+EXPORT_SYMBOL(vfs_xgetattr_nosec);

-EXPORT_SYMBOL(vfs_getattr_nosec);
-
-int vfs_getattr(struct path *path, struct kstat *stat)
+/*
+ * vfs_xgetattr - Get the enhanced basic attributes of a file
+ * @path: The file of interest
+ * @stat: Where to return the statistics
+ *
+ * Ask the filesystem for a file's attributes. The caller must have preset
+ * stat->request_mask and stat->query_flags to indicate what they want.
+ *
+ * If the file is remote, the filesystem can be forced to update the attributes
+ * from the backing store by passing AT_FORCE_ATTR_SYNC in query_flags or can
+ * suppress the update by passing AT_NO_ATTR_SYNC.
+ *
+ * Bits must have been set in stat->request_mask to indicate which attributes
+ * the caller wants retrieving. Any such attribute not requested may be
+ * returned anyway, but the value may be approximate, and, if remote, may not
+ * have been synchronised with the server.
+ *
+ * 0 will be returned on success, and a -ve error code if unsuccessful.
+ */
+int vfs_xgetattr(struct path *path, struct kstat *stat)
{
int retval;

retval = security_inode_getattr(path);
if (retval)
return retval;
- return vfs_getattr_nosec(path, stat);
+ return vfs_xgetattr_nosec(path, stat);
}
+EXPORT_SYMBOL(vfs_xgetattr);

+/**
+ * vfs_getattr - Get the basic attributes of a file
+ * @path: The file of interest
+ * @stat: Where to return the statistics
+ *
+ * Ask the filesystem for a file's attributes. If remote, the filesystem isn't
+ * forced to update its files from the backing store. Only the basic set of
+ * attributes will be retrieved; anyone wanting more must use vfs_xgetattr(),
+ * as must anyone who wants to force attributes to be sync'd with the server.
+ *
+ * 0 will be returned on success, and a -ve error code if unsuccessful.
+ */
+int vfs_getattr(struct path *path, struct kstat *stat)
+{
+ stat->query_flags = 0;
+ stat->request_mask = STATX_BASIC_STATS;
+ return vfs_xgetattr(path, stat);
+}
EXPORT_SYMBOL(vfs_getattr);

-int vfs_fstat(unsigned int fd, struct kstat *stat)
+/**
+ * vfs_fstatx - Get the enhanced basic attributes by file descriptor
+ * @fd: The file descriptor referring to the file of interest
+ * @stat: The result structure to fill in.
+ *
+ * This function is a wrapper around vfs_xgetattr(). The main difference is
+ * that it uses a file descriptor to determine the file location.
+ *
+ * The caller must have preset stat->query_flags and stat->request_mask as for
+ * vfs_xgetattr().
+ *
+ * 0 will be returned on success, and a -ve error code if unsuccessful.
+ */
+int vfs_fstatx(unsigned int fd, struct kstat *stat)
{
struct fd f = fdget_raw(fd);
int error = -EBADF;

if (f.file) {
- error = vfs_getattr(&f.file->f_path, stat);
+ error = vfs_xgetattr(&f.file->f_path, stat);
fdput(f);
}
return error;
}
+EXPORT_SYMBOL(vfs_fstatx);
+
+/**
+ * vfs_fstat - Get basic attributes by file descriptor
+ * @fd: The file descriptor referring to the file of interest
+ * @stat: The result structure to fill in.
+ *
+ * This function is a wrapper around vfs_getattr(). The main difference is
+ * that it uses a file descriptor to determine the file location.
+ *
+ * 0 will be returned on success, and a -ve error code if unsuccessful.
+ */
+int vfs_fstat(unsigned int fd, struct kstat *stat)
+{
+ stat->query_flags = 0;
+ stat->request_mask = STATX_BASIC_STATS;
+ return vfs_fstatx(fd, stat);
+}
EXPORT_SYMBOL(vfs_fstat);

-int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
- int flag)
+/**
+ * vfs_statx - Get basic and extra attributes by filename
+ * @dfd: A file descriptor representing the base dir for a relative filename
+ * @filename: The name of the file of interest
+ * @flags: Flags to control the query
+ * @stat: The result structure to fill in.
+ *
+ * This function is a wrapper around vfs_xgetattr(). The main difference is
+ * that it uses a filename and base directory to determine the file location.
+ * Additionally, the addition of AT_SYMLINK_NOFOLLOW to flags will prevent a
+ * symlink at the given name from being referenced.
+ *
+ * The caller must have preset stat->request_mask as for vfs_xgetattr(). The
+ * flags are also used to load up stat->query_flags.
+ *
+ * 0 will be returned on success, and a -ve error code if unsuccessful.
+ */
+int vfs_statx(int dfd, const char __user *filename, int flags,
+ struct kstat *stat)
{
struct path path;
int error = -EINVAL;
- unsigned int lookup_flags = 0;
+ unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;

- if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
- AT_EMPTY_PATH)) != 0)
- goto out;
+ if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
+ AT_EMPTY_PATH | KSTAT_QUERY_FLAGS)) != 0)
+ return -EINVAL;

- if (!(flag & AT_SYMLINK_NOFOLLOW))
- lookup_flags |= LOOKUP_FOLLOW;
- if (flag & AT_EMPTY_PATH)
+ if (flags & AT_SYMLINK_NOFOLLOW)
+ lookup_flags &= ~LOOKUP_FOLLOW;
+ if (flags & AT_NO_AUTOMOUNT)
+ lookup_flags &= ~LOOKUP_AUTOMOUNT;
+ if (flags & AT_EMPTY_PATH)
lookup_flags |= LOOKUP_EMPTY;
+ stat->query_flags = flags;
+
retry:
error = user_path_at(dfd, filename, lookup_flags, &path);
if (error)
goto out;

- error = vfs_getattr(&path, stat);
+ error = vfs_xgetattr(&path, stat);
path_put(&path);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
@@ -116,17 +235,65 @@ retry:
out:
return error;
}
+EXPORT_SYMBOL(vfs_statx);
+
+/**
+ * vfs_fstatat - Get basic attributes by filename
+ * @dfd: A file descriptor representing the base dir for a relative filename
+ * @filename: The name of the file of interest
+ * @flags: Flags to control the query
+ * @stat: The result structure to fill in.
+ *
+ * This function is a wrapper around vfs_statx(). The difference is that it
+ * preselects basic stats only. The flags are used to load up
+ * stat->query_flags in addition to indicating symlink handling during path
+ * resolution.
+ *
+ * 0 will be returned on success, and a -ve error code if unsuccessful.
+ */
+int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
+ int flags)
+{
+ stat->request_mask = STATX_BASIC_STATS;
+ return vfs_statx(dfd, filename, flags, stat);
+}
EXPORT_SYMBOL(vfs_fstatat);

-int vfs_stat(const char __user *name, struct kstat *stat)
+/**
+ * vfs_stat - Get basic attributes by filename
+ * @filename: The name of the file of interest
+ * @stat: The result structure to fill in.
+ *
+ * This function is a wrapper around vfs_statx(). The difference is that it
+ * preselects basic stats only, terminal symlinks are followed regardless and a
+ * remote filesystem can't be forced to query the server. If such is desired,
+ * vfs_statx() should be used instead.
+ *
+ * 0 will be returned on success, and a -ve error code if unsuccessful.
+ */
+int vfs_stat(const char __user *filename, struct kstat *stat)
{
- return vfs_fstatat(AT_FDCWD, name, stat, 0);
+ stat->request_mask = STATX_BASIC_STATS;
+ return vfs_statx(AT_FDCWD, filename, 0, stat);
}
EXPORT_SYMBOL(vfs_stat);

+/**
+ * vfs_lstat - Get basic attrs by filename, without following terminal symlink
+ * @filename: The name of the file of interest
+ * @stat: The result structure to fill in.
+ *
+ * This function is a wrapper around vfs_statx(). The difference is that it
+ * preselects basic stats only, terminal symlinks are note followed regardless
+ * and a remote filesystem can't be forced to query the server. If such is
+ * desired, vfs_statx() should be used instead.
+ *
+ * 0 will be returned on success, and a -ve error code if unsuccessful.
+ */
int vfs_lstat(const char __user *name, struct kstat *stat)
{
- return vfs_fstatat(AT_FDCWD, name, stat, AT_SYMLINK_NOFOLLOW);
+ stat->request_mask = STATX_BASIC_STATS;
+ return vfs_statx(AT_FDCWD, name, AT_SYMLINK_NOFOLLOW, stat);
}
EXPORT_SYMBOL(vfs_lstat);

@@ -141,7 +308,7 @@ static int cp_old_stat(struct kstat *stat, struct __old_kernel_stat __user * sta
{
static int warncount = 5;
struct __old_kernel_stat tmp;
-
+
if (warncount > 0) {
warncount--;
printk(KERN_WARNING "VFS: Warning: %s using old stat() call. Recompile your binary.\n",
@@ -166,7 +333,7 @@ static int cp_old_stat(struct kstat *stat, struct __old_kernel_stat __user * sta
#if BITS_PER_LONG == 32
if (stat->size > MAX_NON_LFS)
return -EOVERFLOW;
-#endif
+#endif
tmp.st_size = stat->size;
tmp.st_atime = stat->atime.tv_sec;
tmp.st_mtime = stat->mtime.tv_sec;
@@ -443,6 +610,80 @@ SYSCALL_DEFINE4(fstatat64, int, dfd, const char __user *, filename,
}
#endif /* __ARCH_WANT_STAT64 || __ARCH_WANT_COMPAT_STAT64 */

+/*
+ * Set the statx results.
+ */
+static long statx_set_result(struct kstat *stat, struct statx __user *buffer)
+{
+ uid_t uid = from_kuid_munged(current_user_ns(), stat->uid);
+ gid_t gid = from_kgid_munged(current_user_ns(), stat->gid);
+
+#define __put_timestamp(kts, uts) ( \
+ __put_user(kts.tv_sec, uts##_s ) || \
+ __put_user(kts.tv_nsec, uts##_ns ))
+
+ if (__put_user(stat->result_mask, &buffer->st_mask ) ||
+ __put_user(stat->mode, &buffer->st_mode ) ||
+ __clear_user(&buffer->__spare0, sizeof(buffer->__spare0)) ||
+ __put_user(stat->nlink, &buffer->st_nlink ) ||
+ __put_user(uid, &buffer->st_uid ) ||
+ __put_user(gid, &buffer->st_gid ) ||
+ __put_user(stat->information, &buffer->st_information ) ||
+ __put_user(stat->blksize, &buffer->st_blksize ) ||
+ __put_user(MAJOR(stat->rdev), &buffer->st_rdev_major ) ||
+ __put_user(MINOR(stat->rdev), &buffer->st_rdev_minor ) ||
+ __put_user(MAJOR(stat->dev), &buffer->st_dev_major ) ||
+ __put_user(MINOR(stat->dev), &buffer->st_dev_minor ) ||
+ __put_timestamp(stat->atime, &buffer->st_atime ) ||
+ __put_timestamp(stat->btime, &buffer->st_btime ) ||
+ __put_timestamp(stat->ctime, &buffer->st_ctime ) ||
+ __put_timestamp(stat->mtime, &buffer->st_mtime ) ||
+ __put_user(stat->ino, &buffer->st_ino ) ||
+ __put_user(stat->size, &buffer->st_size ) ||
+ __put_user(stat->blocks, &buffer->st_blocks ) ||
+ __put_user(stat->version, &buffer->st_version ) ||
+ __put_user(stat->gen, &buffer->st_gen ) ||
+ __clear_user(&buffer->__spare1, sizeof(buffer->__spare1)))
+ return -EFAULT;
+
+ return 0;
+}
+
+/**
+ * sys_statx - System call to get enhanced stats
+ * @dfd: Base directory to pathwalk from *or* fd to stat.
+ * @filename: File to stat *or* NULL.
+ * @flags: AT_* flags to control pathwalk.
+ * @mask: Parts of statx struct actually required.
+ * @buffer: Result buffer.
+ *
+ * Note that if filename is NULL, then it does the equivalent of fstat() using
+ * dfd to indicate the file of interest.
+ */
+SYSCALL_DEFINE5(statx,
+ int, dfd, const char __user *, filename, unsigned, flags,
+ unsigned int, mask,
+ struct statx __user *, buffer)
+{
+ struct kstat stat;
+ int error;
+
+ if (!access_ok(VERIFY_WRITE, buffer, sizeof(*buffer)))
+ return -EFAULT;
+
+ memset(&stat, 0, sizeof(stat));
+ stat.query_flags = flags;
+ stat.request_mask = mask & STATX_ALL_STATS;
+
+ if (filename)
+ error = vfs_statx(dfd, filename, flags, &stat);
+ else
+ error = vfs_fstatx(dfd, &stat);
+ if (error)
+ return error;
+ return statx_set_result(&stat, buffer);
+}
+
/* Caller is here responsible for sufficient locking (ie. inode->i_lock) */
void __inode_add_bytes(struct inode *inode, loff_t bytes)
{
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 70e61b58baaf..8b2f6df924e9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2827,8 +2827,9 @@ extern const struct inode_operations page_symlink_inode_operations;
extern void kfree_link(void *);
extern int generic_readlink(struct dentry *, char __user *, int);
extern void generic_fillattr(struct inode *, struct kstat *);
-int vfs_getattr_nosec(struct path *path, struct kstat *stat);
+extern int vfs_xgetattr_nosec(struct path *path, struct kstat *stat);
extern int vfs_getattr(struct path *, struct kstat *);
+extern int vfs_xgetattr(struct path *, struct kstat *);
void __inode_add_bytes(struct inode *inode, loff_t bytes);
void inode_add_bytes(struct inode *inode, loff_t bytes);
void __inode_sub_bytes(struct inode *inode, loff_t bytes);
@@ -2845,6 +2846,8 @@ extern int vfs_stat(const char __user *, struct kstat *);
extern int vfs_lstat(const char __user *, struct kstat *);
extern int vfs_fstat(unsigned int, struct kstat *);
extern int vfs_fstatat(int , const char __user *, struct kstat *, int);
+extern int vfs_xstat(int, const char __user *, int, struct kstat *);
+extern int vfs_xfstat(unsigned int, struct kstat *);

extern int __generic_block_fiemap(struct inode *inode,
struct fiemap_extent_info *fieinfo,
diff --git a/include/linux/stat.h b/include/linux/stat.h
index 075cb0c7eb2a..4f1902b0cb94 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -19,6 +19,13 @@
#include <linux/uidgid.h>

struct kstat {
+ u32 query_flags; /* Operational flags */
+#define KSTAT_QUERY_FLAGS (AT_FORCE_ATTR_SYNC | AT_NO_ATTR_SYNC)
+ u32 request_mask; /* What fields the user asked for */
+ u32 result_mask; /* What fields the user got */
+ u32 information;
+ u32 win_attrs; /* Windows file attributes */
+ u32 gen;
u64 ino;
dev_t dev;
umode_t mode;
@@ -27,11 +34,13 @@ struct kstat {
kgid_t gid;
dev_t rdev;
loff_t size;
- struct timespec atime;
+ struct timespec atime;
struct timespec mtime;
struct timespec ctime;
- unsigned long blksize;
- unsigned long long blocks;
+ struct timespec btime; /* File creation time */
+ uint32_t blksize; /* Preferred I/O size */
+ u64 blocks;
+ u64 version; /* Data version */
};

#endif
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index d795472c54d8..f6bfbf74e44d 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -48,6 +48,7 @@ struct stat;
struct stat64;
struct statfs;
struct statfs64;
+struct statx;
struct __sysctl_args;
struct sysinfo;
struct timespec;
@@ -898,4 +899,7 @@ asmlinkage long sys_copy_file_range(int fd_in, loff_t __user *off_in,

asmlinkage long sys_mlock2(unsigned long start, size_t len, int flags);

+asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags,
+ unsigned mask, struct statx __user *buffer);
+
#endif
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index beed138bd359..5c8143b04ff7 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -62,6 +62,8 @@
#define AT_SYMLINK_FOLLOW 0x400 /* Follow symbolic links. */
#define AT_NO_AUTOMOUNT 0x800 /* Suppress terminal automount traversal */
#define AT_EMPTY_PATH 0x1000 /* Allow empty relative pathname */
+#define AT_FORCE_ATTR_SYNC 0x2000 /* Force the attributes to be sync'd with the server */
+#define AT_NO_ATTR_SYNC 0x4000 /* Don't sync attributes with the server */

#endif /* _UAPI_LINUX_FCNTL_H */
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 7fec7e36d921..55ce6607dab6 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -1,6 +1,7 @@
#ifndef _UAPI_LINUX_STAT_H
#define _UAPI_LINUX_STAT_H

+#include <linux/types.h>

#if defined(__KERNEL__) || !defined(__GLIBC__) || (__GLIBC__ < 2)

@@ -41,5 +42,113 @@

#endif

+/*
+ * Structures for the extended file attribute retrieval system call
+ * (statx()).
+ *
+ * The caller passes a mask of what they're specifically interested in as a
+ * parameter to statx(). What statx() actually got will be indicated in
+ * st_mask upon return.
+ *
+ * For each bit in the mask argument:
+ *
+ * - if the datum is not available at all, the field and the bit will both be
+ * cleared;
+ *
+ * - otherwise, if explicitly requested:
+ *
+ * - the datum will be synchronised to the server if AT_FORCE_ATTR_SYNC is
+ * set or if the datum is considered out of date, and
+ *
+ * - the field will be filled in and the bit will be set;
+ *
+ * - otherwise, if not requested, but available in approximate form without any
+ * effort, it will be filled in anyway, and the bit will be set upon return
+ * (it might not be up to date, however, and no attempt will be made to
+ * synchronise the internal state first);
+ *
+ * - otherwise the field and the bit will be cleared before returning.
+ *
+ * Items in STATX_BASIC_STATS may be marked unavailable on return, but they
+ * will have values installed for compatibility purposes so that stat() and
+ * co. can be emulated in userspace.
+ */
+struct statx {
+ /* 0x00 */
+ __u32 st_mask; /* What results were written [uncond] */
+ __u32 st_information; /* Information about the file [uncond] */
+ __u32 st_blksize; /* Preferred general I/O size [uncond] */
+ __u32 st_nlink; /* Number of hard links */
+ /* 0x10 */
+ __u32 st_gen; /* Inode generation number */
+ __u32 st_uid; /* User ID of owner */
+ __u32 st_gid; /* Group ID of owner */
+ __u16 st_mode; /* File mode */
+ __u16 __spare0[1];
+ /* 0x20 */
+ __u64 st_ino; /* Inode number */
+ __u64 st_size; /* File size */
+ __u64 st_blocks; /* Number of 512-byte blocks allocated */
+ __u64 st_version; /* Data version number */
+ /* 0x40 */
+ __s64 st_atime_s; /* Last access time */
+ __s64 st_btime_s; /* File creation time */
+ __s64 st_ctime_s; /* Last attribute change time */
+ __s64 st_mtime_s; /* Last data modification time */
+ /* 0x60 */
+ __s32 st_atime_ns; /* Last access time (ns part) */
+ __s32 st_btime_ns; /* File creation time (ns part) */
+ __s32 st_ctime_ns; /* Last attribute change time (ns part) */
+ __s32 st_mtime_ns; /* Last data modification time (ns part) */
+ /* 0x70 */
+ __u32 st_rdev_major; /* Device ID of special file */
+ __u32 st_rdev_minor;
+ __u32 st_dev_major; /* ID of device containing file [uncond] */
+ __u32 st_dev_minor;
+ /* 0x80 */
+ __u64 __spare1[16]; /* Spare space for future expansion */
+ /* 0x100 */
+};
+
+/*
+ * Flags to be st_mask
+ *
+ * Query request/result mask for statx() and struct statx::st_mask.
+ *
+ * These bits should be set in the mask argument of statx() to request
+ * particular items when calling statx().
+ */
+#define STATX_MODE 0x00000001U /* Want/got st_mode */
+#define STATX_NLINK 0x00000002U /* Want/got st_nlink */
+#define STATX_UID 0x00000004U /* Want/got st_uid */
+#define STATX_GID 0x00000008U /* Want/got st_gid */
+#define STATX_RDEV 0x00000010U /* Want/got st_rdev */
+#define STATX_ATIME 0x00000020U /* Want/got st_atime */
+#define STATX_MTIME 0x00000040U /* Want/got st_mtime */
+#define STATX_CTIME 0x00000080U /* Want/got st_ctime */
+#define STATX_INO 0x00000100U /* Want/got st_ino */
+#define STATX_SIZE 0x00000200U /* Want/got st_size */
+#define STATX_BLOCKS 0x00000400U /* Want/got st_blocks */
+#define STATX_BASIC_STATS 0x000007ffU /* The stuff in the normal stat struct */
+#define STATX_BTIME 0x00000800U /* Want/got st_btime */
+#define STATX_VERSION 0x00001000U /* Want/got st_version */
+#define STATX_GEN 0x00002000U /* Want/got st_gen */
+#define STATX_ALL_STATS 0x00003fffU /* All supported stats */
+
+/*
+ * Flags to be found in st_information
+ *
+ * These give information about the features or the state of a file that might
+ * be of use to ordinary userspace programs such as GUIs or ls rather than
+ * specialised tools.
+ */
+#define STATX_INFO_ENCRYPTED 0x00000001U /* File is encrypted */
+#define STATX_INFO_TEMPORARY 0x00000002U /* File is temporary */
+#define STATX_INFO_FABRICATED 0x00000004U /* File was made up by filesystem */
+#define STATX_INFO_KERNEL_API 0x00000008U /* File is kernel API (eg: procfs/sysfs) */
+#define STATX_INFO_REMOTE 0x00000010U /* File is remote */
+#define STATX_INFO_AUTOMOUNT 0x00000020U /* Dir is automount trigger */
+#define STATX_INFO_AUTODIR 0x00000040U /* Dir provides unlisted automounts */
+#define STATX_INFO_NONSYSTEM_OWNERSHIP 0x00000080U /* File has non-system ownership details */

#endif /* _UAPI_LINUX_STAT_H */
diff --git a/samples/Makefile b/samples/Makefile
index 48001d7e23f0..d2ebb4e48d19 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -2,4 +2,4 @@

obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ livepatch/ \
hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/ \
- configfs/
+ configfs/ statx/
diff --git a/samples/statx/Makefile b/samples/statx/Makefile
new file mode 100644
index 000000000000..6765dabc4c8d
--- /dev/null
+++ b/samples/statx/Makefile
@@ -0,0 +1,10 @@
+# kbuild trick to avoid linker error. Can be omitted if a module is built.
+obj- := dummy.o
+
+# List of programs to build
+hostprogs-y := test-statx
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
+
+HOSTCFLAGS_test-statx.o += -I$(objtree)/usr/include
diff --git a/samples/statx/test-statx.c b/samples/statx/test-statx.c
new file mode 100644
index 000000000000..38ef23c12e7d
--- /dev/null
+++ b/samples/statx/test-statx.c
@@ -0,0 +1,243 @@
+/* Test the statx() system call
+ *
+ * Copyright (C) 2015 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#define _GNU_SOURCE
+#define _ATFILE_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <linux/stat.h>
+#include <linux/fcntl.h>
+#include <sys/stat.h>
+
+#define AT_FORCE_ATTR_SYNC 0x2000
+#define AT_NO_ATTR_SYNC 0x4000
+
+static __attribute__((unused))
+ssize_t statx(int dfd, const char *filename, unsigned flags,
+ unsigned int mask, struct statx *buffer)
+{
+ return syscall(__NR_statx, dfd, filename, flags, mask, buffer);
+}
+
+static void print_time(const char *field, __s64 tv_sec, __s32 tv_nsec)
+{
+ struct tm tm;
+ time_t tim;
+ char buffer[100];
+ int len;
+
+ tim = tv_sec;
+ if (!localtime_r(&tim, &tm)) {
+ perror("localtime_r");
+ exit(1);
+ }
+ len = strftime(buffer, 100, "%F %T", &tm);
+ if (len == 0) {
+ perror("strftime");
+ exit(1);
+ }
+ printf("%s", field);
+ fwrite(buffer, 1, len, stdout);
+ printf(".%09u", tv_nsec);
+ len = strftime(buffer, 100, "%z", &tm);
+ if (len == 0) {
+ perror("strftime2");
+ exit(1);
+ }
+ fwrite(buffer, 1, len, stdout);
+ printf("\n");
+}
+
+static void dump_statx(struct statx *stx)
+{
+ char buffer[256], ft = '?';
+
+ printf("results=%x\n", stx->st_mask);
+
+ printf(" ");
+ if (stx->st_mask & STATX_SIZE)
+ printf(" Size: %-15llu", (unsigned long long)stx->st_size);
+ if (stx->st_mask & STATX_BLOCKS)
+ printf(" Blocks: %-10llu", (unsigned long long)stx->st_blocks);
+ printf(" IO Block: %-6llu ", (unsigned long long)stx->st_blksize);
+ if (stx->st_mask & STATX_MODE) {
+ switch (stx->st_mode & S_IFMT) {
+ case S_IFIFO: printf(" FIFO\n"); ft = 'p'; break;
+ case S_IFCHR: printf(" character special file\n"); ft = 'c'; break;
+ case S_IFDIR: printf(" directory\n"); ft = 'd'; break;
+ case S_IFBLK: printf(" block special file\n"); ft = 'b'; break;
+ case S_IFREG: printf(" regular file\n"); ft = '-'; break;
+ case S_IFLNK: printf(" symbolic link\n"); ft = 'l'; break;
+ case S_IFSOCK: printf(" socket\n"); ft = 's'; break;
+ default:
+ printf("unknown type (%o)\n", stx->st_mode & S_IFMT);
+ break;
+ }
+ }
+
+ sprintf(buffer, "%02x:%02x", stx->st_dev_major, stx->st_dev_minor);
+ printf("Device: %-15s", buffer);
+ if (stx->st_mask & STATX_INO)
+ printf(" Inode: %-11llu", (unsigned long long) stx->st_ino);
+ if (stx->st_mask & STATX_SIZE)
+ printf(" Links: %-5u", stx->st_nlink);
+ if (stx->st_mask & STATX_RDEV)
+ printf(" Device type: %u,%u", stx->st_rdev_major, stx->st_rdev_minor);
+ printf("\n");
+
+ if (stx->st_mask & STATX_MODE)
+ printf("Access: (%04o/%c%c%c%c%c%c%c%c%c%c) ",
+ stx->st_mode & 07777,
+ ft,
+ stx->st_mode & S_IRUSR ? 'r' : '-',
+ stx->st_mode & S_IWUSR ? 'w' : '-',
+ stx->st_mode & S_IXUSR ? 'x' : '-',
+ stx->st_mode & S_IRGRP ? 'r' : '-',
+ stx->st_mode & S_IWGRP ? 'w' : '-',
+ stx->st_mode & S_IXGRP ? 'x' : '-',
+ stx->st_mode & S_IROTH ? 'r' : '-',
+ stx->st_mode & S_IWOTH ? 'w' : '-',
+ stx->st_mode & S_IXOTH ? 'x' : '-');
+ if (stx->st_mask & STATX_UID)
+ printf("Uid: %5d ", stx->st_uid);
+ if (stx->st_mask & STATX_GID)
+ printf("Gid: %5d\n", stx->st_gid);
+
+ if (stx->st_mask & STATX_ATIME)
+ print_time("Access: ", stx->st_atime_s, stx->st_atime_ns);
+ if (stx->st_mask & STATX_MTIME)
+ print_time("Modify: ", stx->st_mtime_s, stx->st_mtime_ns);
+ if (stx->st_mask & STATX_CTIME)
+ print_time("Change: ", stx->st_ctime_s, stx->st_ctime_ns);
+ if (stx->st_mask & STATX_BTIME)
+ print_time(" Birth: ", stx->st_btime_s, stx->st_btime_ns);
+
+ if (stx->st_mask & STATX_VERSION)
+ printf("Data version: %llxh\n",
+ (unsigned long long)stx->st_version);
+
+ if (stx->st_mask & STATX_GEN)
+ printf("Inode gen : %xh\n", stx->st_gen);
+
+ if (stx->st_information) {
+ unsigned char bits;
+ int loop, byte;
+
+ static char info_representation[32 + 1] =
+ /* STATX_INFO_ flags: */
+ "????????" /* 31-24 0x00000000-ff000000 */
+ "????????" /* 23-16 0x00000000-00ff0000 */
+ "????????" /* 15- 8 0x00000000-0000ff00 */
+ "ndmrkfte" /* 7- 0 0x00000000-000000ff */
+ ;
+
+ printf("Information: %08x (", stx->st_information);
+ for (byte = 32 - 8; byte >= 0; byte -= 8) {
+ bits = stx->st_information >> byte;
+ for (loop = 7; loop >= 0; loop--) {
+ int bit = byte + loop;
+
+ if (bits & 0x80)
+ putchar(info_representation[31 - bit]);
+ else
+ putchar('-');
+ bits <<= 1;
+ }
+ if (byte)
+ putchar(' ');
+ }
+ printf(")\n");
+ }
+
+ printf("IO-blocksize: blksize=%u\n", stx->st_blksize);
+}
+
+static void dump_hex(unsigned long long *data, int from, int to)
+{
+ unsigned offset, print_offset = 1, col = 0;
+
+ from /= 8;
+ to = (to + 7) / 8;
+
+ for (offset = from; offset < to; offset++) {
+ if (print_offset) {
+ printf("%04x: ", offset * 8);
+ print_offset = 0;
+ }
+ printf("%016llx", data[offset]);
+ col++;
+ if ((col & 3) == 0) {
+ printf("\n");
+ print_offset = 1;
+ } else {
+ printf(" ");
+ }
+ }
+
+ if (!print_offset)
+ printf("\n");
+}
+
+int main(int argc, char **argv)
+{
+ struct statx stx;
+ int ret, raw = 0, atflag = AT_SYMLINK_NOFOLLOW;
+
+ unsigned int mask = STATX_ALL_STATS;
+
+ for (argv++; *argv; argv++) {
+ if (strcmp(*argv, "-F") == 0) {
+ atflag |= AT_FORCE_ATTR_SYNC;
+ continue;
+ }
+ if (strcmp(*argv, "-N") == 0) {
+ atflag |= AT_NO_ATTR_SYNC;
+ continue;
+ }
+ if (strcmp(*argv, "-L") == 0) {
+ atflag &= ~AT_SYMLINK_NOFOLLOW;
+ continue;
+ }
+ if (strcmp(*argv, "-O") == 0) {
+ mask &= ~STATX_BASIC_STATS;
+ continue;
+ }
+ if (strcmp(*argv, "-A") == 0) {
+ atflag |= AT_NO_AUTOMOUNT;
+ continue;
+ }
+ if (strcmp(*argv, "-R") == 0) {
+ raw = 1;
+ continue;
+ }
+
+ memset(&stx, 0xbf, sizeof(stx));
+ ret = statx(AT_FDCWD, *argv, atflag, mask, &stx);
+ printf("statx(%s) = %d\n", *argv, ret);
+ if (ret < 0) {
+ perror(*argv);
+ exit(1);
+ }
+
+ if (raw)
+ dump_hex((unsigned long long *)&stx, 0, sizeof(stx));
+
+ dump_statx(&stx);
+ }
+ return 0;
+}