From 4c5b479975212065ef39786e115fde42847e95a9 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 7 Apr 2021 14:36:42 +0200 Subject: vfs: add fileattr ops There's a substantial amount of boilerplate in filesystems handling FS_IOC_[GS]ETFLAGS/ FS_IOC_FS[GS]ETXATTR ioctls. Also due to userspace buffers being involved in the ioctl API this is difficult to stack, as shown by overlayfs issues related to these ioctls. Introduce a new internal API named "fileattr" (fsxattr can be confused with xattr, xflags is inappropriate, since this is more than just flags). There's significant overlap between flags and xflags and this API handles the conversions automatically, so filesystems may choose which one to use. In ->fileattr_get() a hint is provided to the filesystem whether flags or xattr are being requested by userspace, but in this series this hint is ignored by all filesystems, since generating all the attributes is cheap. If a filesystem doesn't implemement the fileattr API, just fall back to f_op->ioctl(). When all filesystems are converted, the fallback can be removed. 32bit compat ioctls are now handled by the generic code as well. Signed-off-by: Miklos Szeredi --- Documentation/filesystems/locking.rst | 11 ++++++++--- Documentation/filesystems/vfs.rst | 15 +++++++++++++++ 2 files changed, 23 insertions(+), 3 deletions(-) (limited to 'Documentation') diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index b7dcc86c92a4..729ce492b662 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -80,13 +80,16 @@ prototypes:: struct file *, unsigned open_flag, umode_t create_mode); int (*tmpfile) (struct inode *, struct dentry *, umode_t); + int (*fileattr_set)(struct user_namespace *mnt_userns, + struct dentry *dentry, struct fileattr *fa); + int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa); locking rules: all may block -============ ============================================= +============= ============================================= ops i_rwsem(inode) -============ ============================================= +============= ============================================= lookup: shared create: exclusive link: exclusive (both) @@ -107,7 +110,9 @@ fiemap: no update_time: no atomic_open: shared (exclusive if O_CREAT is set in open flags) tmpfile: no -============ ============================================= +fileattr_get: no or exclusive +fileattr_set: exclusive +============= ============================================= Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index 2049bbf5e388..14c31eced416 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -441,6 +441,9 @@ As of kernel 2.6.22, the following members are defined: unsigned open_flag, umode_t create_mode); int (*tmpfile) (struct user_namespace *, struct inode *, struct dentry *, umode_t); int (*set_acl)(struct user_namespace *, struct inode *, struct posix_acl *, int); + int (*fileattr_set)(struct user_namespace *mnt_userns, + struct dentry *dentry, struct fileattr *fa); + int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa); }; Again, all methods are called without any locks being held, unless @@ -588,6 +591,18 @@ otherwise noted. atomically creating, opening and unlinking a file in given directory. +``fileattr_get`` + called on ioctl(FS_IOC_GETFLAGS) and ioctl(FS_IOC_FSGETXATTR) to + retrieve miscellaneous file flags and attributes. Also called + before the relevant SET operation to check what is being changed + (in this case with i_rwsem locked exclusive). If unset, then + fall back to f_op->ioctl(). + +``fileattr_set`` + called on ioctl(FS_IOC_SETFLAGS) and ioctl(FS_IOC_FSSETXATTR) to + change miscellaneous file flags and attributes. Callers hold + i_rwsem exclusive. If unset, then fall back to f_op->ioctl(). + The Address Space Object ======================== -- cgit