On Wed, 2022-08-10 at 11:00 +0800, JunChao Sun wrote:

On Sat, Aug 6, 2022 at 2:37 AM Jeff Layton [off-list ref] wrote:

quoted

From: Jeff Layton <redacted>

Claim one of the spare fields in struct statx to hold a 64-bit change

quoted

attribute. When statx requests this attribute, do an
inode_query_iversion and fill the result in the field.

I guess, is it better to update the corresponding part of the man-pages...?

Yes. If we end up accepting a patch like this, we'll need to update the
statx(2) manpage. We'll probably also want to add support for it to the
/bin/stat coreutils command as well.

At this point, I'm trying to put together some xfstests so we can ensure
that this feature doesn't regress (if we take it).

quoted

Also update the test-statx.c program to fetch the change attribute as
well.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/stat.c                 | 7 +++++++
 include/linux/stat.h      | 1 +
 include/uapi/linux/stat.h | 3 ++-
 samples/vfs/test-statx.c  | 4 +++-
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/stat.c b/fs/stat.c
index 9ced8860e0f3..976e0a59ab23 100644
--- a/fs/stat.c
+++ b/fs/stat.c

@@ -17,6 +17,7 @@
 #include <linux/syscalls.h>
 #include <linux/pagemap.h>
 #include <linux/compat.h>
+#include <linux/iversion.h>

 #include <linux/uaccess.h>
 #include <asm/unistd.h>

@@ -118,6 +119,11 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
        stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT |
                                  STATX_ATTR_DAX);

+       if ((request_mask & STATX_CHGATTR) && IS_I_VERSION(inode)) {
+               stat->result_mask |= STATX_CHGATTR;
+               stat->chgattr = inode_query_iversion(inode);
+       }
+
        mnt_userns = mnt_user_ns(path->mnt);
        if (inode->i_op->getattr)
                return inode->i_op->getattr(mnt_userns, path, stat,

@@ -611,6 +617,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
        tmp.stx_dev_major = MAJOR(stat->dev);
        tmp.stx_dev_minor = MINOR(stat->dev);
        tmp.stx_mnt_id = stat->mnt_id;
+       tmp.stx_chgattr = stat->chgattr;

        return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0;
 }

diff --git a/include/linux/stat.h b/include/linux/stat.h
index 7df06931f25d..4a17887472f6 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h

@@ -50,6 +50,7 @@ struct kstat {
        struct timespec64 btime;                        /* File creation time */
        u64             blocks;
        u64             mnt_id;
+       u64             chgattr;
 };

 #endif

diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 1500a0f58041..b45243a0fbc5 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h

@@ -124,7 +124,7 @@ struct statx {
        __u32   stx_dev_minor;
        /* 0x90 */
        __u64   stx_mnt_id;
-       __u64   __spare2;
+       __u64   stx_chgattr;    /* Inode change attribute */
        /* 0xa0 */
        __u64   __spare3[12];   /* Spare space for future expansion */
        /* 0x100 */

@@ -152,6 +152,7 @@ struct statx {
 #define STATX_BASIC_STATS      0x000007ffU     /* The stuff in the normal stat struct */
 #define STATX_BTIME            0x00000800U     /* Want/got stx_btime */
 #define STATX_MNT_ID           0x00001000U     /* Got stx_mnt_id */
+#define STATX_CHGATTR          0x00002000U     /* Want/git stx_chgattr */

 #define STATX__RESERVED                0x80000000U     /* Reserved for future struct statx expansion */

diff --git a/samples/vfs/test-statx.c b/samples/vfs/test-statx.c
index 49c7a46cee07..767208d2f564 100644
--- a/samples/vfs/test-statx.c
+++ b/samples/vfs/test-statx.c

@@ -109,6 +109,8 @@ static void dump_statx(struct statx *stx)
                printf(" Inode: %-11llu", (unsigned long long) stx->stx_ino);
        if (stx->stx_mask & STATX_NLINK)
                printf(" Links: %-5u", stx->stx_nlink);
+       if (stx->stx_mask & STATX_CHGATTR)
+               printf(" Change Attr: 0x%llx", stx->stx_chgattr);
        if (stx->stx_mask & STATX_TYPE) {
                switch (stx->stx_mode & S_IFMT) {
                case S_IFBLK:

@@ -218,7 +220,7 @@ int main(int argc, char **argv)
        struct statx stx;
        int ret, raw = 0, atflag = AT_SYMLINK_NOFOLLOW;

-       unsigned int mask = STATX_BASIC_STATS | STATX_BTIME;
+       unsigned int mask = STATX_BASIC_STATS | STATX_BTIME | STATX_CHGATTR;

        for (argv++; *argv; argv++) {
                if (strcmp(*argv, "-F") == 0) {
--

2.37.1

-- 
Jeff Layton [off-list ref]