On Fri, Mar 31, 2017 at 06:32:17PM +0100, David Howells wrote:
> Include a mask in struct stat to indicate which bits of stx_attributes the
> filesystem actually supports.
>
> This would also be useful if we add another system call that allows you to
> do a 'bulk attribute set' and pass in a statx struct with the masks
> appropriately set to say what you want to set.
>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> ---
>
> fs/ext4/inode.c | 6 ++++++
> fs/stat.c | 1 +
> include/linux/stat.h | 1 +
> include/uapi/linux/stat.h | 4 ++--
> samples/statx/test-statx.c | 12 ++++++++----
> 5 files changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 5d02b922afa3..349f97ae3c87 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5413,6 +5413,12 @@ int ext4_getattr(const struct path *path, struct kstat *stat,
> if (flags & EXT4_NODUMP_FL)
> stat->attributes |= STATX_ATTR_NODUMP;
>
> + stat->attributes_mask |= (STATX_ATTR_APPEND |
> + STATX_ATTR_COMPRESSED |
ext4 doesn't actually support compressed files.
(I know, the feature/inode flags exist, but there's no code and afaik
probably never will be...)
--D
> + STATX_ATTR_ENCRYPTED |
> + STATX_ATTR_IMMUTABLE |
> + STATX_ATTR_NODUMP);
> +
> generic_fillattr(inode, stat);
> return 0;
> }
> diff --git a/fs/stat.c b/fs/stat.c
> index 0c7e6cdc435c..c6c963b2546b 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -527,6 +527,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
> tmp.stx_ino = stat->ino;
> tmp.stx_size = stat->size;
> tmp.stx_blocks = stat->blocks;
> + tmp.stx_attributes_mask = stat->attributes_mask;
> tmp.stx_atime.tv_sec = stat->atime.tv_sec;
> tmp.stx_atime.tv_nsec = stat->atime.tv_nsec;
> tmp.stx_btime.tv_sec = stat->btime.tv_sec;
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index c76e524fb34b..64b6b3aece21 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -26,6 +26,7 @@ struct kstat {
> unsigned int nlink;
> uint32_t blksize; /* Preferred I/O size */
> u64 attributes;
> + u64 attributes_mask;
> #define KSTAT_ATTR_FS_IOC_FLAGS \
> (STATX_ATTR_COMPRESSED | \
> STATX_ATTR_IMMUTABLE | \
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 0869b9eaa8ce..d538897b8e08 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -114,7 +114,7 @@ struct statx {
> __u64 stx_ino; /* Inode number */
> __u64 stx_size; /* File size */
> __u64 stx_blocks; /* Number of 512-byte blocks allocated */
> - __u64 __spare1[1];
> + __u64 stx_attributes_mask; /* Mask to show what's supported in stx_attributes */
> /* 0x40 */
> struct statx_timestamp stx_atime; /* Last access time */
> struct statx_timestamp stx_btime; /* File creation time */
> @@ -155,7 +155,7 @@ struct statx {
> #define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */
>
> /*
> - * Attributes to be found in stx_attributes
> + * Attributes to be found in stx_attributes and masked in stx_attributes_mask.
> *
> * 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
> diff --git a/samples/statx/test-statx.c b/samples/statx/test-statx.c
> index 8571d766331d..d4d77b09412c 100644
> --- a/samples/statx/test-statx.c
> +++ b/samples/statx/test-statx.c
> @@ -141,8 +141,8 @@ static void dump_statx(struct statx *stx)
> if (stx->stx_mask & STATX_BTIME)
> print_time(" Birth: ", &stx->stx_btime);
>
> - if (stx->stx_attributes) {
> - unsigned char bits;
> + if (stx->stx_attributes_mask) {
> + unsigned char bits, mbits;
> int loop, byte;
>
> static char attr_representation[64 + 1] =
> @@ -160,14 +160,18 @@ static void dump_statx(struct statx *stx)
> printf("Attributes: %016llx (", stx->stx_attributes);
> for (byte = 64 - 8; byte >= 0; byte -= 8) {
> bits = stx->stx_attributes >> byte;
> + mbits = stx->stx_attributes_mask >> byte;
> for (loop = 7; loop >= 0; loop--) {
> int bit = byte + loop;
>
> - if (bits & 0x80)
> + if (!(mbits & 0x80))
> + putchar('.'); /* Not supported */
> + else if (bits & 0x80)
> putchar(attr_representation[63 - bit]);
> else
> - putchar('-');
> + putchar('-'); /* Not set */
> bits <<= 1;
> + mbits <<= 1;
> }
> if (byte)
> putchar(' ');
>
> --
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