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The current way of setting and getting posix acls through the generic xattr interface is error prone and type unsafe. The vfs needs to interpret and fixup posix acls before storing or reporting it to userspace. Various hacks exist to make this work. The code is hard to understand and difficult to maintain in it's current form. Instead of making this work by hacking posix acls through xattr handlers we are building a dedicated posix acl api around the get and set inode operations. This removes a lot of hackiness and makes the codepaths easier to maintain. A lot of background can be found in [1]. The current inode operation for getting posix acls takes an inode argument but various filesystems (e.g., 9p, cifs, overlayfs) need access to the dentry. In contrast to the ->set_acl() inode operation we cannot simply extend ->get_acl() to take a dentry argument. The ->get_acl() inode operation is called from: acl_permission_check() -> check_acl() -> get_acl() which is part of generic_permission() which in turn is part of inode_permission(). Both generic_permission() and inode_permission() are called in the ->permission() handler of various filesystems (e.g., overlayfs). So simply passing a dentry argument to ->get_acl() would amount to also having to pass a dentry argument to ->permission(). We should avoid this unnecessary change. So instead of extending the existing inode operation rename it from ->get_acl() to ->get_inode_acl() and add a ->get_acl() method later that passes a dentry argument and which filesystems that need access to the dentry can implement instead of ->get_inode_acl(). Filesystems like cifs which allow setting and getting posix acls but not using them for permission checking during lookup can simply not implement ->get_inode_acl(). This is intended to be a non-functional change. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Suggested-by/Inspired-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
209 lines
5.3 KiB
C
209 lines
5.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/fs/ext2/file.c
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*
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* Copyright (C) 1992, 1993, 1994, 1995
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* Remy Card (card@masi.ibp.fr)
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* Laboratoire MASI - Institut Blaise Pascal
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* Universite Pierre et Marie Curie (Paris VI)
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*
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* from
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*
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* linux/fs/minix/file.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* ext2 fs regular file handling primitives
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*
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* 64-bit file support on 64-bit platforms by Jakub Jelinek
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* (jj@sunsite.ms.mff.cuni.cz)
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*/
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#include <linux/time.h>
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#include <linux/pagemap.h>
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#include <linux/dax.h>
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#include <linux/quotaops.h>
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#include <linux/iomap.h>
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#include <linux/uio.h>
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#include "ext2.h"
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#include "xattr.h"
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#include "acl.h"
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#ifdef CONFIG_FS_DAX
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static ssize_t ext2_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
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{
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struct inode *inode = iocb->ki_filp->f_mapping->host;
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ssize_t ret;
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if (!iov_iter_count(to))
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return 0; /* skip atime */
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inode_lock_shared(inode);
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ret = dax_iomap_rw(iocb, to, &ext2_iomap_ops);
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inode_unlock_shared(inode);
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file_accessed(iocb->ki_filp);
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return ret;
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}
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static ssize_t ext2_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
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{
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struct file *file = iocb->ki_filp;
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struct inode *inode = file->f_mapping->host;
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ssize_t ret;
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inode_lock(inode);
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ret = generic_write_checks(iocb, from);
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if (ret <= 0)
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goto out_unlock;
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ret = file_remove_privs(file);
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if (ret)
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goto out_unlock;
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ret = file_update_time(file);
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if (ret)
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goto out_unlock;
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ret = dax_iomap_rw(iocb, from, &ext2_iomap_ops);
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if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
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i_size_write(inode, iocb->ki_pos);
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mark_inode_dirty(inode);
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}
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out_unlock:
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inode_unlock(inode);
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if (ret > 0)
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ret = generic_write_sync(iocb, ret);
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return ret;
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}
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/*
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* The lock ordering for ext2 DAX fault paths is:
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*
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* mmap_lock (MM)
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* sb_start_pagefault (vfs, freeze)
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* address_space->invalidate_lock
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* address_space->i_mmap_rwsem or page_lock (mutually exclusive in DAX)
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* ext2_inode_info->truncate_mutex
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*
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* The default page_lock and i_size verification done by non-DAX fault paths
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* is sufficient because ext2 doesn't support hole punching.
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*/
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static vm_fault_t ext2_dax_fault(struct vm_fault *vmf)
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{
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struct inode *inode = file_inode(vmf->vma->vm_file);
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vm_fault_t ret;
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bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
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(vmf->vma->vm_flags & VM_SHARED);
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if (write) {
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sb_start_pagefault(inode->i_sb);
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file_update_time(vmf->vma->vm_file);
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}
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filemap_invalidate_lock_shared(inode->i_mapping);
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ret = dax_iomap_fault(vmf, PE_SIZE_PTE, NULL, NULL, &ext2_iomap_ops);
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filemap_invalidate_unlock_shared(inode->i_mapping);
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if (write)
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sb_end_pagefault(inode->i_sb);
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return ret;
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}
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static const struct vm_operations_struct ext2_dax_vm_ops = {
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.fault = ext2_dax_fault,
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/*
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* .huge_fault is not supported for DAX because allocation in ext2
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* cannot be reliably aligned to huge page sizes and so pmd faults
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* will always fail and fail back to regular faults.
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*/
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.page_mkwrite = ext2_dax_fault,
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.pfn_mkwrite = ext2_dax_fault,
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};
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static int ext2_file_mmap(struct file *file, struct vm_area_struct *vma)
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{
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if (!IS_DAX(file_inode(file)))
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return generic_file_mmap(file, vma);
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file_accessed(file);
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vma->vm_ops = &ext2_dax_vm_ops;
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return 0;
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}
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#else
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#define ext2_file_mmap generic_file_mmap
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#endif
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/*
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* Called when filp is released. This happens when all file descriptors
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* for a single struct file are closed. Note that different open() calls
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* for the same file yield different struct file structures.
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*/
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static int ext2_release_file (struct inode * inode, struct file * filp)
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{
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if (filp->f_mode & FMODE_WRITE) {
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mutex_lock(&EXT2_I(inode)->truncate_mutex);
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ext2_discard_reservation(inode);
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mutex_unlock(&EXT2_I(inode)->truncate_mutex);
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}
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return 0;
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}
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int ext2_fsync(struct file *file, loff_t start, loff_t end, int datasync)
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{
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int ret;
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struct super_block *sb = file->f_mapping->host->i_sb;
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ret = generic_file_fsync(file, start, end, datasync);
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if (ret == -EIO)
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/* We don't really know where the IO error happened... */
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ext2_error(sb, __func__,
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"detected IO error when writing metadata buffers");
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return ret;
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}
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static ssize_t ext2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
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{
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#ifdef CONFIG_FS_DAX
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if (IS_DAX(iocb->ki_filp->f_mapping->host))
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return ext2_dax_read_iter(iocb, to);
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#endif
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return generic_file_read_iter(iocb, to);
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}
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static ssize_t ext2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
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{
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#ifdef CONFIG_FS_DAX
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if (IS_DAX(iocb->ki_filp->f_mapping->host))
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return ext2_dax_write_iter(iocb, from);
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#endif
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return generic_file_write_iter(iocb, from);
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}
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const struct file_operations ext2_file_operations = {
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.llseek = generic_file_llseek,
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.read_iter = ext2_file_read_iter,
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.write_iter = ext2_file_write_iter,
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.unlocked_ioctl = ext2_ioctl,
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#ifdef CONFIG_COMPAT
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.compat_ioctl = ext2_compat_ioctl,
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#endif
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.mmap = ext2_file_mmap,
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.open = dquot_file_open,
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.release = ext2_release_file,
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.fsync = ext2_fsync,
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.get_unmapped_area = thp_get_unmapped_area,
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.splice_read = generic_file_splice_read,
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.splice_write = iter_file_splice_write,
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};
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const struct inode_operations ext2_file_inode_operations = {
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.listxattr = ext2_listxattr,
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.getattr = ext2_getattr,
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.setattr = ext2_setattr,
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.get_inode_acl = ext2_get_acl,
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.set_acl = ext2_set_acl,
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.fiemap = ext2_fiemap,
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.fileattr_get = ext2_fileattr_get,
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.fileattr_set = ext2_fileattr_set,
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};
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