Commit 36f05cab authored by Jeff Layton's avatar Jeff Layton Committed by Andrew Morton
Browse files

tmpfs: add support for an i_version counter 

NFSv4 mandates a change attribute to avoid problems with timestamp
granularity, which Linux implements using the i_version counter. This is
particularly important when the underlying filesystem is fast.

Give tmpfs an i_version counter. Since it doesn't have to be persistent,
we can just turn on SB_I_VERSION and sprinkle some inode_inc_iversion
calls in the right places.

Also, while there is no formal spec for xattrs, most implementations
update the ctime on setxattr. Fix shmem_xattr_handler_set to update the
ctime and bump the i_version appropriately.

Link: https://lkml.kernel.org/r/20220909130031.15477-1-jlayton@kernel.org


Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 5934ec13

fs/posix_acl.c

+3 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 
#include <linux/user_namespace.h>

#include <linux/namei.h>

#include <linux/mnt_idmapping.h>

#include <linux/iversion.h>



static struct posix_acl **acl_by_type(struct inode *inode, int type)

{
@@ -1073,6 +1074,8 @@ int simple_set_acl(struct user_namespace *mnt_userns, struct inode *inode, 
	}



	inode->i_ctime = current_time(inode);

	if (IS_I_VERSION(inode))

		inode_inc_iversion(inode);

	set_cached_acl(inode, type, acl);

	return 0;

}

mm/shmem.c

+28 −3
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 
#include <linux/hugetlb.h>

#include <linux/fs_parser.h>

#include <linux/swapfile.h>

#include <linux/iversion.h>

#include "swap.h"



static struct vfsmount *shm_mnt;
@@ -1030,6 +1031,7 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 
{

	shmem_undo_range(inode, lstart, lend, false);

	inode->i_ctime = inode->i_mtime = current_time(inode);

	inode_inc_iversion(inode);

}

EXPORT_SYMBOL_GPL(shmem_truncate_range);
@@ -1074,6 +1076,8 @@ static int shmem_setattr(struct user_namespace *mnt_userns, 
	struct inode *inode = d_inode(dentry);

	struct shmem_inode_info *info = SHMEM_I(inode);

	int error;

	bool update_mtime = false;

	bool update_ctime = true;



	error = setattr_prepare(&init_user_ns, dentry, attr);

	if (error)
@@ -1094,7 +1098,9 @@ static int shmem_setattr(struct user_namespace *mnt_userns, 
			if (error)

				return error;

			i_size_write(inode, newsize);

			inode->i_ctime = inode->i_mtime = current_time(inode);

			update_mtime = true;

		} else {

			update_ctime = false;

		}

		if (newsize <= oldsize) {

			loff_t holebegin = round_up(newsize, PAGE_SIZE);
@@ -1114,6 +1120,12 @@ static int shmem_setattr(struct user_namespace *mnt_userns, 
	setattr_copy(&init_user_ns, inode, attr);

	if (attr->ia_valid & ATTR_MODE)

		error = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);

	if (!error && update_ctime) {

		inode->i_ctime = current_time(inode);

		if (update_mtime)

			inode->i_mtime = inode->i_ctime;

		inode_inc_iversion(inode);

	}

	return error;

}
@@ -2890,6 +2902,7 @@ shmem_mknod(struct user_namespace *mnt_userns, struct inode *dir, 
		error = 0;

		dir->i_size += BOGO_DIRENT_SIZE;

		dir->i_ctime = dir->i_mtime = current_time(dir);

		inode_inc_iversion(dir);

		d_instantiate(dentry, inode);

		dget(dentry); /* Extra count - pin the dentry in core */

	}
@@ -2965,6 +2978,7 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentr 


	dir->i_size += BOGO_DIRENT_SIZE;

	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);

	inode_inc_iversion(dir);

	inc_nlink(inode);

	ihold(inode);	/* New dentry reference */

	dget(dentry);		/* Extra pinning count for the created dentry */
@@ -2982,6 +2996,7 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry) 


	dir->i_size -= BOGO_DIRENT_SIZE;

	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);

	inode_inc_iversion(dir);

	drop_nlink(inode);

	dput(dentry);	/* Undo the count from "create" - this does all the work */

	return 0;
@@ -3071,6 +3086,8 @@ static int shmem_rename2(struct user_namespace *mnt_userns, 
	old_dir->i_ctime = old_dir->i_mtime =

	new_dir->i_ctime = new_dir->i_mtime =

	inode->i_ctime = current_time(old_dir);

	inode_inc_iversion(old_dir);

	inode_inc_iversion(new_dir);

	return 0;

}
@@ -3123,6 +3140,7 @@ static int shmem_symlink(struct user_namespace *mnt_userns, struct inode *dir, 
	}

	dir->i_size += BOGO_DIRENT_SIZE;

	dir->i_ctime = dir->i_mtime = current_time(dir);

	inode_inc_iversion(dir);

	d_instantiate(dentry, inode);

	dget(dentry);

	return 0;
@@ -3194,6 +3212,7 @@ static int shmem_fileattr_set(struct user_namespace *mnt_userns, 


	shmem_set_inode_flags(inode, info->fsflags);

	inode->i_ctime = current_time(inode);

	inode_inc_iversion(inode);

	return 0;

}
@@ -3257,9 +3276,15 @@ static int shmem_xattr_handler_set(const struct xattr_handler *handler, 
				   size_t size, int flags)

{

	struct shmem_inode_info *info = SHMEM_I(inode);

	int err;



	name = xattr_full_name(handler, name);

	return simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);

	err = simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);

	if (!err) {

		inode->i_ctime = current_time(inode);

		inode_inc_iversion(inode);

	}

	return err;

}



static const struct xattr_handler shmem_security_xattr_handler = {
@@ -3722,7 +3747,7 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc) 
		sb->s_flags |= SB_NOUSER;

	}

	sb->s_export_op = &shmem_export_ops;

	sb->s_flags |= SB_NOSEC;

	sb->s_flags |= SB_NOSEC | SB_I_VERSION;

#else

	sb->s_flags |= SB_NOUSER;

#endif