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: Jeff 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: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 5af3380..efb88a5 100644 (file)
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -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;
 }

diff --git a/mm/shmem.c b/mm/shmem.c
index 3d0b729..275899b 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -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