From: "Darrick J. Wong" <djwong@kernel.org>
To: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Cc: linux-bcachefs@vger.kernel.org,
"Christian Brauner" <brauner@kernel.org>,
"Jan Kara" <jack@suse.cz>,
linux-fsdevel@vger.kernel.org, "Jonathan Corbet" <corbet@lwn.net>,
linux-btrfs@vger.kernel.org, "Brian Foster" <bfoster@redhat.com>,
"Kent Overstreet" <kent.overstreet@linux.dev>,
linux-doc@vger.kernel.org, "Josef Bacik" <josef@toxicpanda.com>,
linux-kernel@vger.kernel.org, "Chris Mason" <clm@fb.com>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"David Sterba" <dsterba@suse.com>,
"Jaegeuk Kim" <jaegeuk@kernel.org>,
linux-f2fs-devel@lists.sourceforge.net, kernel-team@meta.com,
"Mickaël Salaün" <mic@digikod.net>
Subject: Re: [f2fs-dev] [PATCH v3 01/13] fs: fiemap: add physical_length field to extents
Date: Tue, 9 Apr 2024 09:22:32 -0700 [thread overview]
Message-ID: <20240409162232.GA6367@frogsfrogsfrogs> (raw)
In-Reply-To: <1ba5bfccccbf4ff792f178268badde056797d0c4.1712126039.git.sweettea-kernel@dorminy.me>
On Wed, Apr 03, 2024 at 03:22:42AM -0400, Sweet Tea Dorminy wrote:
> Some filesystems support compressed extents which have a larger logical
> size than physical, and for those filesystems, it can be useful for
> userspace to know how much space those extents actually use. For
> instance, the compsize [1] tool for btrfs currently uses btrfs-internal,
> root-only ioctl to find the actual disk space used by a file; it would
> be better and more useful for this information to require fewer
> privileges and to be usable on more filesystems. Therefore, use one of
> the padding u64s in the fiemap extent structure to return the actual
> physical length; and, for now, return this as equal to the logical
> length.
>
> [1] https://github.com/kilobyte/compsize
>
> Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
> ---
> Documentation/filesystems/fiemap.rst | 28 +++++++++++++++++-------
> fs/ioctl.c | 3 ++-
> include/uapi/linux/fiemap.h | 32 ++++++++++++++++++++++------
> 3 files changed, 47 insertions(+), 16 deletions(-)
>
> diff --git a/Documentation/filesystems/fiemap.rst b/Documentation/filesystems/fiemap.rst
> index 93fc96f760aa..c2bfa107c8d7 100644
> --- a/Documentation/filesystems/fiemap.rst
> +++ b/Documentation/filesystems/fiemap.rst
> @@ -80,14 +80,24 @@ Each extent is described by a single fiemap_extent structure as
> returned in fm_extents::
>
> struct fiemap_extent {
> - __u64 fe_logical; /* logical offset in bytes for the start of
> - * the extent */
> - __u64 fe_physical; /* physical offset in bytes for the start
> - * of the extent */
> - __u64 fe_length; /* length in bytes for the extent */
> - __u64 fe_reserved64[2];
> - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */
> - __u32 fe_reserved[3];
> + /*
> + * logical offset in bytes for the start of
> + * the extent from the beginning of the file
> + */
> + __u64 fe_logical;
> + /*
> + * physical offset in bytes for the start
> + * of the extent from the beginning of the disk
> + */
> + __u64 fe_physical;
> + /* logical length in bytes for this extent */
> + __u64 fe_logical_length;
> + /* physical length in bytes for this extent */
> + __u64 fe_physical_length;
> + __u64 fe_reserved64[1];
> + /* FIEMAP_EXTENT_* flags for this extent */
> + __u32 fe_flags;
> + __u32 fe_reserved[3];
> };
>
> All offsets and lengths are in bytes and mirror those on disk. It is valid
> @@ -175,6 +185,8 @@ FIEMAP_EXTENT_MERGED
> userspace would be highly inefficient, the kernel will try to merge most
> adjacent blocks into 'extents'.
>
> +FIEMAP_EXTENT_HAS_PHYS_LEN
> + This will be set if the file system populated the physical length field.
Just out of curiosity, should filesystems set this flag and
fe_physical_length if fe_physical_length == fe_logical_length?
Or just leave both blank?
> VFS -> File System Implementation
> ---------------------------------
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 661b46125669..8afd32e1a27a 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -138,7 +138,8 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical,
> memset(&extent, 0, sizeof(extent));
> extent.fe_logical = logical;
> extent.fe_physical = phys;
> - extent.fe_length = len;
> + extent.fe_logical_length = len;
> + extent.fe_physical_length = len;
> extent.fe_flags = flags;
>
> dest += fieinfo->fi_extents_mapped;
> diff --git a/include/uapi/linux/fiemap.h b/include/uapi/linux/fiemap.h
> index 24ca0c00cae3..3079159b8e94 100644
> --- a/include/uapi/linux/fiemap.h
> +++ b/include/uapi/linux/fiemap.h
> @@ -14,14 +14,30 @@
>
> #include <linux/types.h>
>
> +/*
> + * For backward compatibility, where the member of the struct was called
> + * fe_length instead of fe_logical_length.
> + */
> +#define fe_length fe_logical_length
This #define has global scope; are you sure this isn't going to cause a
weird build problem downstream with some program that declares an
unrelated fe_length symbol?
> +
> struct fiemap_extent {
> - __u64 fe_logical; /* logical offset in bytes for the start of
> - * the extent from the beginning of the file */
> - __u64 fe_physical; /* physical offset in bytes for the start
> - * of the extent from the beginning of the disk */
> - __u64 fe_length; /* length in bytes for this extent */
> - __u64 fe_reserved64[2];
> - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */
> + /*
> + * logical offset in bytes for the start of
> + * the extent from the beginning of the file
> + */
> + __u64 fe_logical;
> + /*
> + * physical offset in bytes for the start
> + * of the extent from the beginning of the disk
> + */
> + __u64 fe_physical;
> + /* logical length in bytes for this extent */
> + __u64 fe_logical_length;
Or why not just leave the field name the same since the "logical length
in bytes" comment is present both here in the header and again in the
documentation?
--D
> + /* physical length in bytes for this extent */
> + __u64 fe_physical_length;
> + __u64 fe_reserved64[1];
> + /* FIEMAP_EXTENT_* flags for this extent */
> + __u32 fe_flags;
> __u32 fe_reserved[3];
> };
>
> @@ -66,5 +82,7 @@ struct fiemap {
> * merged for efficiency. */
> #define FIEMAP_EXTENT_SHARED 0x00002000 /* Space shared with other
> * files. */
> +#define FIEMAP_EXTENT_HAS_PHYS_LEN 0x00004000 /* Physical length is valid
> + * and set by FS. */
>
> #endif /* _UAPI_LINUX_FIEMAP_H */
> --
> 2.43.0
>
>
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next prev parent reply other threads:[~2024-04-09 16:22 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-03 7:22 [f2fs-dev] [PATCH v3 00/13] fiemap extension for more physical information Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 01/13] fs: fiemap: add physical_length field to extents Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 16:57 ` Brian Foster
2024-04-09 16:22 ` Darrick J. Wong [this message]
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 02/13] fs: fiemap: update fiemap_fill_next_extent() signature Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 16:58 ` Brian Foster
[not found] ` <BDD29EBF-3A5F-4241-B9F2-789605D99817@dilger.ca>
2024-04-05 19:06 ` [f2fs-dev] [PATCH v3 02/13] " Kent Overstreet
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 03/13] fs: fiemap: add new COMPRESSED extent state Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 04/13] btrfs: fiemap: emit new COMPRESSED state Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 05/13] btrfs: fiemap: return extent physical size Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 06/13] nilfs2: fiemap: return correct extent physical length Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 07/13] ext4: " Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 11:22 ` Jan Kara
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 08/13] f2fs: fiemap: add physical length to trace_f2fs_fiemap Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 09/13] f2fs: fiemap: return correct extent physical length Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 10/13] ocfs2: " Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 11:25 ` Jan Kara
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 11/13] bcachefs: " Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 17:00 ` Brian Foster
2024-04-03 18:15 ` Kent Overstreet
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 12/13] f2fs: fiemap: emit new COMPRESSED state Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-03 7:22 ` [f2fs-dev] [PATCH v3 13/13] bcachefs: " Sweet Tea Dorminy via Linux-f2fs-devel
[not found] ` <7CF0A3D0-50E7-448F-A992-90B9168D557F@dilger.ca>
2024-04-06 5:20 ` Kent Overstreet
2024-04-03 8:29 ` [f2fs-dev] [PATCH v3 00/13] fiemap extension for more physical information Gao Xiang
2024-04-03 15:11 ` Sweet Tea Dorminy via Linux-f2fs-devel
2024-04-04 0:43 ` Gao Xiang
2024-04-03 18:17 ` Kent Overstreet
2024-04-03 18:20 ` Darrick J. Wong
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