Re: [PATCH v6 6/6] fs: introduce file_getattr and file_setattr syscalls
From: "Darrick J. Wong" <djwong@kernel.org>
Date: 2025-07-01 18:43:18
Also in:
linux-fsdevel, linux-xfs, lkml, selinux
On Mon, Jun 30, 2025 at 06:20:16PM +0200, Andrey Albershteyn wrote:
From: Andrey Albershteyn <redacted> Introduce file_getattr() and file_setattr() syscalls to manipulate inode extended attributes. The syscalls takes pair of file descriptor and pathname. Then it operates on inode opened accroding to openat() semantics. The struct fsx_fileattr is passed to obtain/change extended attributes. This is an alternative to FS_IOC_FSSETXATTR ioctl with a difference that file don't need to be open as we can reference it with a path instead of fd. By having this we can manipulated inode extended attributes not only on regular files but also on special ones. This is not possible with FS_IOC_FSSETXATTR ioctl as with special files we can not call ioctl() directly on the filesystem inode using fd. This patch adds two new syscalls which allows userspace to get/set extended inode attributes on special files by using parent directory and a path - *at() like syscall. CC: linux-api@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: linux-xfs@vger.kernel.org Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org> Acked-by: Arnd Bergmann <arnd@arndb.de> ---
<snip syscall table>
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diff --git a/fs/file_attr.c b/fs/file_attr.c index 62f08872d4ad..fda9d847eee5 100644 --- a/fs/file_attr.c +++ b/fs/file_attr.c@@ -3,6 +3,10 @@ #include <linux/security.h> #include <linux/fscrypt.h> #include <linux/fileattr.h> +#include <linux/syscalls.h> +#include <linux/namei.h> + +#include "internal.h" /** * fileattr_fill_xflags - initialize fileattr with xflags@@ -89,6 +93,19 @@ int vfs_fileattr_get(struct dentry *dentry, struct fileattr *fa) } EXPORT_SYMBOL(vfs_fileattr_get); +static void fileattr_to_fsx_fileattr(const struct fileattr *fa, + struct fsx_fileattr *fsx)
Er... "fsx_fileattr" is the struct that the system call uses? That's a little confusing considering that xfs already has a xfs_fill_fsxattr function that actually fills a struct fileattr. That could be renamed xfs_fill_fileattr. I dunno. There's a part of me that would really rather that the file_getattr and file_setattr syscalls operate on a struct file_attr. More whining/bikeshedding to come. <snip stuff that looks ok to me> <<well, I still dislike the CLASS(fd, fd)(fd) syntax...>>
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diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 0098b0ce8ccb..0784f2033ba4 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h@@ -148,6 +148,24 @@ struct fsxattr { unsigned char fsx_pad[8]; }; +/* + * Variable size structure for file_[sg]et_attr(). + * + * Note. This is alternative to the structure 'struct fileattr'/'struct fsxattr'. + * As this structure is passed to/from userspace with its size, this can + * be versioned based on the size. + */ +struct fsx_fileattr { + __u32 fsx_xflags; /* xflags field value (get/set) */
Should this to be __u64 from the start? Seeing as (a) this struct is not already a multiple of 8 bytes and (b) it's likely that we'll have to add a u64 field at some point. That would also address brauner's comment about padding. --D
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+ __u32 fsx_extsize; /* extsize field value (get/set)*/ + __u32 fsx_nextents; /* nextents field value (get) */ + __u32 fsx_projid; /* project identifier (get/set) */ + __u32 fsx_cowextsize; /* CoW extsize field value (get/set) */ +}; + +#define FSX_FILEATTR_SIZE_VER0 20 +#define FSX_FILEATTR_SIZE_LATEST FSX_FILEATTR_SIZE_VER0 + /* * Flags for the fsx_xflags field */diff --git a/scripts/syscall.tbl b/scripts/syscall.tbl index 580b4e246aec..d1ae5e92c615 100644 --- a/scripts/syscall.tbl +++ b/scripts/syscall.tbl@@ -408,3 +408,5 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common file_getattr sys_file_getattr +469 common file_setattr sys_file_setattr-- 2.47.2