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Message-ID: <CAEg-Je96OKs_LOXorNVj1a1=e+1f=-gw34v4VWNOmfKXc6PLSQ@mail.gmail.com>
Date: Fri, 8 Mar 2024 06:42:27 -0500
From: Neal Gompa <neal@...pa.dev>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: linux-fsdevel@...r.kernel.org, linux-bcachefs@...r.kernel.org,
linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
Josef Bacik <josef@...icpanda.com>, Miklos Szeredi <mszeredi@...hat.com>,
Christian Brauner <brauner@...nel.org>, David Howells <dhowells@...hat.com>
Subject: Re: [PATCH v2] statx: stx_subvol
On Thu, Mar 7, 2024 at 9:29 PM Kent Overstreet
<kent.overstreet@...ux.dev> wrote:
>
> Add a new statx field for (sub)volume identifiers, as implemented by
> btrfs and bcachefs.
>
> This includes bcachefs support; we'll definitely want btrfs support as
> well.
>
> Link: https://lore.kernel.org/linux-fsdevel/2uvhm6gweyl7iyyp2xpfryvcu2g3padagaeqcbiavjyiis6prl@yjm725bizncq/
> Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
> Cc: Josef Bacik <josef@...icpanda.com>
> Cc: Miklos Szeredi <mszeredi@...hat.com>
> Cc: Christian Brauner <brauner@...nel.org>
> Cc: David Howells <dhowells@...hat.com>
> Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
> ---
> fs/bcachefs/fs.c | 3 +++
> fs/stat.c | 1 +
> include/linux/stat.h | 1 +
> include/uapi/linux/stat.h | 4 +++-
> 4 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/fs/bcachefs/fs.c b/fs/bcachefs/fs.c
> index 3f073845bbd7..6a542ed43e2c 100644
> --- a/fs/bcachefs/fs.c
> +++ b/fs/bcachefs/fs.c
> @@ -840,6 +840,9 @@ static int bch2_getattr(struct mnt_idmap *idmap,
> stat->blksize = block_bytes(c);
> stat->blocks = inode->v.i_blocks;
>
> + stat->subvol = inode->ei_subvol;
> + stat->result_mask |= STATX_SUBVOL;
> +
> if (request_mask & STATX_BTIME) {
> stat->result_mask |= STATX_BTIME;
> stat->btime = bch2_time_to_timespec(c, inode->ei_inode.bi_otime);
> diff --git a/fs/stat.c b/fs/stat.c
> index 77cdc69eb422..70bd3e888cfa 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -658,6 +658,7 @@ 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_subvol = stat->subvol;
>
> return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0;
> }
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index 52150570d37a..bf92441dbad2 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -53,6 +53,7 @@ struct kstat {
> u32 dio_mem_align;
> u32 dio_offset_align;
> u64 change_cookie;
> + u64 subvol;
> };
>
> /* These definitions are internal to the kernel for now. Mainly used by nfsd. */
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 2f2ee82d5517..67626d535316 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -126,8 +126,9 @@ struct statx {
> __u64 stx_mnt_id;
> __u32 stx_dio_mem_align; /* Memory buffer alignment for direct I/O */
> __u32 stx_dio_offset_align; /* File offset alignment for direct I/O */
> + __u64 stx_subvol; /* Subvolume identifier */
> /* 0xa0 */
> - __u64 __spare3[12]; /* Spare space for future expansion */
> + __u64 __spare3[11]; /* Spare space for future expansion */
> /* 0x100 */
> };
>
> @@ -155,6 +156,7 @@ struct statx {
> #define STATX_MNT_ID 0x00001000U /* Got stx_mnt_id */
> #define STATX_DIOALIGN 0x00002000U /* Want/got direct I/O alignment info */
> #define STATX_MNT_ID_UNIQUE 0x00004000U /* Want/got extended stx_mount_id */
> +#define STATX_SUBVOL 0x00008000U /* Want/got stx_subvol */
>
> #define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */
>
> --
> 2.43.0
>
>
I think it's generally expected that patches that touch different
layers are split up. That is, we should have a patch that adds the
capability and a separate patch that enables it in bcachefs. This also
helps make it clearer to others how a new feature should be plumbed
into a filesystem.
I would prefer it to be split up in this manner for this reason.
--
真実はいつも一つ!/ Always, there's only one truth!
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