On 2025-02-21 20:15:24, Amir Goldstein wrote: > On Fri, Feb 21, 2025 at 7:13 PM Darrick J. Wong <djwong@xxxxxxxxxx> wrote: > > > > On Tue, Feb 11, 2025 at 06:22:47PM +0100, Andrey Albershteyn wrote: > > > From: Andrey Albershteyn <aalbersh@xxxxxxxxxx> > > > > > > Introduce getfsxattrat and setfsxattrat syscalls to manipulate inode > > > extended attributes/flags. The syscalls take parent directory fd and > > > path to the child together with struct fsxattr. > > > > > > 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. > > > > > > Also, as vfs_fileattr_set() is now will be called on special files > > > too, let's forbid any other attributes except projid and nextents > > > (symlink can have an extent). > > > > > > CC: linux-api@xxxxxxxxxxxxxxx > > > CC: linux-fsdevel@xxxxxxxxxxxxxxx > > > CC: linux-xfs@xxxxxxxxxxxxxxx > > > Signed-off-by: Andrey Albershteyn <aalbersh@xxxxxxxxxx> > > > --- > > > v1: > > > https://lore.kernel.org/linuxppc-dev/20250109174540.893098-1-aalbersh@xxxxxxxxxx/ > > > > > > Previous discussion: > > > https://lore.kernel.org/linux-xfs/20240520164624.665269-2-aalbersh@xxxxxxxxxx/ > > > > > > XFS has project quotas which could be attached to a directory. All > > > new inodes in these directories inherit project ID set on parent > > > directory. > > > > > > The project is created from userspace by opening and calling > > > FS_IOC_FSSETXATTR on each inode. This is not possible for special > > > files such as FIFO, SOCK, BLK etc. Therefore, some inodes are left > > > with empty project ID. Those inodes then are not shown in the quota > > > accounting but still exist in the directory. Moreover, in the case > > > when special files are created in the directory with already > > > existing project quota, these inode inherit extended attributes. > > > This than leaves them with these attributes without the possibility > > > to clear them out. This, in turn, prevents userspace from > > > re-creating quota project on these existing files. > > > --- > > > Changes in v3: > > > - Remove unnecessary "dfd is dir" check as it checked in user_path_at() > > > - Remove unnecessary "same filesystem" check > > > - Use CLASS() instead of directly calling fdget/fdput > > > - Link to v2: https://lore.kernel.org/r/20250122-xattrat-syscall-v2-1-5b360d4fbcb2@xxxxxxxxxx > > > --- > > > arch/alpha/kernel/syscalls/syscall.tbl | 2 + > > > arch/arm/tools/syscall.tbl | 2 + > > > arch/arm64/tools/syscall_32.tbl | 2 + > > > arch/m68k/kernel/syscalls/syscall.tbl | 2 + > > > arch/microblaze/kernel/syscalls/syscall.tbl | 2 + > > > arch/mips/kernel/syscalls/syscall_n32.tbl | 2 + > > > arch/mips/kernel/syscalls/syscall_n64.tbl | 2 + > > > arch/mips/kernel/syscalls/syscall_o32.tbl | 2 + > > > arch/parisc/kernel/syscalls/syscall.tbl | 2 + > > > arch/powerpc/kernel/syscalls/syscall.tbl | 2 + > > > arch/s390/kernel/syscalls/syscall.tbl | 2 + > > > arch/sh/kernel/syscalls/syscall.tbl | 2 + > > > arch/sparc/kernel/syscalls/syscall.tbl | 2 + > > > arch/x86/entry/syscalls/syscall_32.tbl | 2 + > > > arch/x86/entry/syscalls/syscall_64.tbl | 2 + > > > arch/xtensa/kernel/syscalls/syscall.tbl | 2 + > > > fs/inode.c | 75 +++++++++++++++++++++++++++++ > > > fs/ioctl.c | 16 +++++- > > > include/linux/fileattr.h | 1 + > > > include/linux/syscalls.h | 4 ++ > > > include/uapi/asm-generic/unistd.h | 8 ++- > > > 21 files changed, 133 insertions(+), 3 deletions(-) > > > > > > > <cut to the syscall definitions> > > > > > diff --git a/fs/inode.c b/fs/inode.c > > > index 6b4c77268fc0ecace4ac78a9ca777fbffc277f4a..b2dddd9db4fabaf67a6cbf541a86978b290411ec 100644 > > > --- a/fs/inode.c > > > +++ b/fs/inode.c > > > @@ -23,6 +23,9 @@ > > > #include <linux/rw_hint.h> > > > #include <linux/seq_file.h> > > > #include <linux/debugfs.h> > > > +#include <linux/syscalls.h> > > > +#include <linux/fileattr.h> > > > +#include <linux/namei.h> > > > #include <trace/events/writeback.h> > > > #define CREATE_TRACE_POINTS > > > #include <trace/events/timestamp.h> > > > @@ -2953,3 +2956,75 @@ umode_t mode_strip_sgid(struct mnt_idmap *idmap, > > > return mode & ~S_ISGID; > > > } > > > EXPORT_SYMBOL(mode_strip_sgid); > > > + > > > +SYSCALL_DEFINE4(getfsxattrat, int, dfd, const char __user *, filename, > > > + struct fsxattr __user *, fsx, unsigned int, at_flags) > > > > Should the kernel require userspace to pass the size of the fsx buffer? > > That way we avoid needing to rev the interface when we decide to grow > > the structure. > > > > This makes sense to me, but I see that Andreas proposed other ways, > as long as we have a plan on how to extend the struct if we need more space. > > Andrey, I am sorry to bring this up in v3, but I would like to request > two small changes before merging this API. > > This patch by Pali [1] adds fsx_xflags_mask for the filesystem to > report the supported set of xflags. > > It was argued that we can make this change with the existing ioctl, > because it is not going to break xfs_io -c lsattr/chattr, which is fine, > but I think that we should merge the fsx_xflags_mask change along > with getfsxattrat() which is a new UAPI. > > The second request is related to setfsxattrat(). > With current FS_IOC_FSSETXATTR, IIUC, xfs ignores unsupported > fsx_xflags. I think this needs to be fixed before merging setfsxattrat(). > It's ok that a program calling FS_IOC_FSSETXATTR will not know > if unsupported flags will be ignored, because that's the way it is, > but I think that setfsxattrat() must return -EINVAL for trying to > set unsupported xflags. > > As I explained in [2] I think it is fine if FS_IOC_FSSETXATTR > will also start returning -EINVAL for unsupported flags, but I would > like setfsxattrat() to make that a guarantee. > > There was an open question, what does fsx_xflags_mask mean > for setfsxattrat() - it is a mask like in inode_set_flags() as Andreas > suggested? I think that would be a good idea. > > Thanks, > Amir. > > [1] https://lore.kernel.org/linux-fsdevel/20250216164029.20673-4-pali@xxxxxxxxxx/ > [2] https://lore.kernel.org/linux-fsdevel/CAOQ4uxjwQJiKAqyjEmKUnq-VihyeSsxyEy2F+J38NXwrAXurFQ@xxxxxxxxxxxxxx/ > I'm fine with making Pali's patchset a dependency for this syscall, as if vfs_fileattr_set() will start returning EINVAL on unsupported flags this syscall will pass it through (ioctls will need to ignore it). And as these syscalls use fsxattr anyway the fsx_xflags_mask field will be here. -- - Andrey
