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Date: Tue, 04 Oct 2022 10:42:39 +1100
From: "NeilBrown" <neilb@...e.de>
To: "Jeff Layton" <jlayton@...nel.org>
Cc: tytso@....edu, adilger.kernel@...ger.ca, djwong@...nel.org,
david@...morbit.com, trondmy@...merspace.com,
viro@...iv.linux.org.uk, zohar@...ux.ibm.com, xiubli@...hat.com,
chuck.lever@...cle.com, lczerner@...hat.com, jack@...e.cz,
bfields@...ldses.org, brauner@...nel.org, fweimer@...hat.com,
linux-btrfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, ceph-devel@...r.kernel.org,
linux-ext4@...r.kernel.org, linux-nfs@...r.kernel.org,
linux-xfs@...r.kernel.org, "Jeff Layton" <jlayton@...hat.com>
Subject: Re: [PATCH v6 7/9] vfs: expose STATX_VERSION to userland
On Fri, 30 Sep 2022, Jeff Layton wrote:
> From: Jeff Layton <jlayton@...hat.com>
>
> Claim one of the spare fields in struct statx to hold a 64-bit inode
> version attribute. When userland requests STATX_VERSION, copy the
> value from the kstat struct there, and stop masking off
> STATX_ATTR_VERSION_MONOTONIC.
>
> Update the test-statx sample program to output the change attr and
> MountId.
>
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
> fs/stat.c | 12 +++---------
> include/linux/stat.h | 9 ---------
> include/uapi/linux/stat.h | 6 ++++--
> samples/vfs/test-statx.c | 8 ++++++--
> 4 files changed, 13 insertions(+), 22 deletions(-)
>
> diff --git a/fs/stat.c b/fs/stat.c
> index e7f8cd4b24e1..8396c372022f 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -593,11 +593,9 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
>
> memset(&tmp, 0, sizeof(tmp));
>
> - /* STATX_VERSION is kernel-only for now */
> - tmp.stx_mask = stat->result_mask & ~STATX_VERSION;
> + tmp.stx_mask = stat->result_mask;
> tmp.stx_blksize = stat->blksize;
> - /* STATX_ATTR_VERSION_MONOTONIC is kernel-only for now */
> - tmp.stx_attributes = stat->attributes & ~STATX_ATTR_VERSION_MONOTONIC;
> + tmp.stx_attributes = stat->attributes;
> tmp.stx_nlink = stat->nlink;
> tmp.stx_uid = from_kuid_munged(current_user_ns(), stat->uid);
> tmp.stx_gid = from_kgid_munged(current_user_ns(), stat->gid);
> @@ -621,6 +619,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
> tmp.stx_mnt_id = stat->mnt_id;
> tmp.stx_dio_mem_align = stat->dio_mem_align;
> tmp.stx_dio_offset_align = stat->dio_offset_align;
> + tmp.stx_version = stat->version;
>
> return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0;
> }
> @@ -636,11 +635,6 @@ int do_statx(int dfd, struct filename *filename, unsigned int flags,
> if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
> return -EINVAL;
>
> - /* STATX_VERSION is kernel-only for now. Ignore requests
> - * from userland.
> - */
> - mask &= ~STATX_VERSION;
> -
> error = vfs_statx(dfd, filename, flags, &stat, mask);
> if (error)
> return error;
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index 4e9428d86a3a..69c79e4fd1b1 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -54,13 +54,4 @@ struct kstat {
> u32 dio_offset_align;
> u64 version;
> };
> -
> -/* These definitions are internal to the kernel for now. Mainly used by nfsd. */
> -
> -/* mask values */
> -#define STATX_VERSION 0x40000000U /* Want/got stx_change_attr */
> -
> -/* file attribute values */
> -#define STATX_ATTR_VERSION_MONOTONIC 0x8000000000000000ULL /* version monotonically increases */
> -
> #endif
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 7cab2c65d3d7..4a0a1f27c059 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -127,7 +127,8 @@ struct statx {
> __u32 stx_dio_mem_align; /* Memory buffer alignment for direct I/O */
> __u32 stx_dio_offset_align; /* File offset alignment for direct I/O */
> /* 0xa0 */
> - __u64 __spare3[12]; /* Spare space for future expansion */
> + __u64 stx_version; /* Inode change attribute */
> + __u64 __spare3[11]; /* Spare space for future expansion */
> /* 0x100 */
> };
>
> @@ -154,6 +155,7 @@ struct statx {
> #define STATX_BTIME 0x00000800U /* Want/got stx_btime */
> #define STATX_MNT_ID 0x00001000U /* Got stx_mnt_id */
> #define STATX_DIOALIGN 0x00002000U /* Want/got direct I/O alignment info */
> +#define STATX_VERSION 0x00004000U /* Want/got stx_version */
>
> #define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */
>
> @@ -189,6 +191,6 @@ struct statx {
> #define STATX_ATTR_MOUNT_ROOT 0x00002000 /* Root of a mount */
> #define STATX_ATTR_VERITY 0x00100000 /* [I] Verity protected file */
> #define STATX_ATTR_DAX 0x00200000 /* File is currently in DAX state */
> -
> +#define STATX_ATTR_VERSION_MONOTONIC 0x00400000 /* stx_version increases w/ every change */
>
> #endif /* _UAPI_LINUX_STAT_H */
> diff --git a/samples/vfs/test-statx.c b/samples/vfs/test-statx.c
> index 49c7a46cee07..bdbc371c9774 100644
> --- a/samples/vfs/test-statx.c
> +++ b/samples/vfs/test-statx.c
> @@ -107,6 +107,8 @@ static void dump_statx(struct statx *stx)
> printf("Device: %-15s", buffer);
> if (stx->stx_mask & STATX_INO)
> printf(" Inode: %-11llu", (unsigned long long) stx->stx_ino);
> + if (stx->stx_mask & STATX_MNT_ID)
> + printf(" MountId: %llx", stx->stx_mnt_id);
> if (stx->stx_mask & STATX_NLINK)
> printf(" Links: %-5u", stx->stx_nlink);
> if (stx->stx_mask & STATX_TYPE) {
> @@ -145,7 +147,9 @@ static void dump_statx(struct statx *stx)
> if (stx->stx_mask & STATX_CTIME)
> print_time("Change: ", &stx->stx_ctime);
> if (stx->stx_mask & STATX_BTIME)
> - print_time(" Birth: ", &stx->stx_btime);
> + print_time("Birth: ", &stx->stx_btime);
> + if (stx->stx_mask & STATX_VERSION)
> + printf("Inode Version: 0x%llx\n", stx->stx_version);
Why hex? not decimal? I don't really care but it seems like an odd choice.
>
> if (stx->stx_attributes_mask) {
> unsigned char bits, mbits;
> @@ -218,7 +222,7 @@ 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_MNT_ID | STATX_VERSION;
>
> for (argv++; *argv; argv++) {
> if (strcmp(*argv, "-F") == 0) {
> --
> 2.37.3
>
>
Reviewed-by: NeilBrown <neilb@...e.de>
Thanks,
NeilBrown
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