Merge branch 'work.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs xattr updates from Al Viro:
 "xattr stuff from Andreas

  This completes the switch to xattr_handler ->get()/->set() from
  ->getxattr/->setxattr/->removexattr"

* 'work.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: Remove {get,set,remove}xattr inode operations
  xattr: Stop calling {get,set,remove}xattr inode operations
  vfs: Check for the IOP_XATTR flag in listxattr
  xattr: Add __vfs_{get,set,remove}xattr helpers
  libfs: Use IOP_XATTR flag for empty directory handling
  vfs: Use IOP_XATTR flag for bad-inode handling
  vfs: Add IOP_XATTR inode operations flag
  vfs: Move xattr_resolve_name to the front of fs/xattr.c
  ecryptfs: Switch to generic xattr handlers
  sockfs: Get rid of getxattr iop
  sockfs: getxattr: Fail with -EOPNOTSUPP for invalid attribute names
  kernfs: Switch to generic xattr handlers
  hfs: Switch to generic xattr handlers
  jffs2: Remove jffs2_{get,set,remove}xattr macros
  xattr: Remove unnecessary NULL attribute name check

65 files changed, 338 insertions, 545 deletions

diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 0e6ad3019711..afaa4b6de801 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -967,9 +967,6 @@ const struct inode_operations v9fs_dir_inode_operations_dotl = {
 	.rename = v9fs_vfs_rename,
 	.getattr = v9fs_vfs_getattr_dotl,
 	.setattr = v9fs_vfs_setattr_dotl,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
-	.removexattr = generic_removexattr,
 	.listxattr = v9fs_listxattr,
 	.get_acl = v9fs_iop_get_acl,
 };
@@ -977,9 +974,6 @@ const struct inode_operations v9fs_dir_inode_operations_dotl = {
 const struct inode_operations v9fs_file_inode_operations_dotl = {
 	.getattr = v9fs_vfs_getattr_dotl,
 	.setattr = v9fs_vfs_setattr_dotl,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
-	.removexattr = generic_removexattr,
 	.listxattr = v9fs_listxattr,
 	.get_acl = v9fs_iop_get_acl,
 };
@@ -989,8 +983,5 @@ const struct inode_operations v9fs_symlink_inode_operations_dotl = {
 	.get_link = v9fs_vfs_get_link_dotl,
 	.getattr = v9fs_vfs_getattr_dotl,
 	.setattr = v9fs_vfs_setattr_dotl,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
-	.removexattr = generic_removexattr,
 	.listxattr = v9fs_listxattr,
 };
diff --git a/fs/bad_inode.c b/fs/bad_inode.c
index 3ba385eaa26e..7bb153c33459 100644
--- a/fs/bad_inode.c
+++ b/fs/bad_inode.c
@@ -100,29 +100,12 @@ static int bad_inode_setattr(struct dentry *direntry, struct iattr *attrs)
 	return -EIO;
 }
 
-static int bad_inode_setxattr(struct dentry *dentry, struct inode *inode,
-		const char *name, const void *value, size_t size, int flags)
-{
-	return -EIO;
-}
-
-static ssize_t bad_inode_getxattr(struct dentry *dentry, struct inode *inode,
-			const char *name, void *buffer, size_t size)
-{
-	return -EIO;
-}
-
 static ssize_t bad_inode_listxattr(struct dentry *dentry, char *buffer,
 			size_t buffer_size)
 {
 	return -EIO;
 }
 
-static int bad_inode_removexattr(struct dentry *dentry, const char *name)
-{
-	return -EIO;
-}
-
 static const struct inode_operations bad_inode_ops =
 {
 	.create		= bad_inode_create,
@@ -142,10 +125,7 @@ static const struct inode_operations bad_inode_ops =
 	.permission	= bad_inode_permission,
 	.getattr	= bad_inode_getattr,
 	.setattr	= bad_inode_setattr,
-	.setxattr	= bad_inode_setxattr,
-	.getxattr	= bad_inode_getxattr,
 	.listxattr	= bad_inode_listxattr,
-	.removexattr	= bad_inode_removexattr,
 };
 
 
@@ -175,6 +155,7 @@ void make_bad_inode(struct inode *inode)
 	inode->i_atime = inode->i_mtime = inode->i_ctime =
 		current_fs_time(inode->i_sb);
 	inode->i_op = &bad_inode_ops;	
+	inode->i_opflags &= ~IOP_XATTR;
 	inode->i_fop = &bad_file_ops;	
 }
 EXPORT_SYMBOL(make_bad_inode);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a0d3016f6c26..994fe5af160b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -10556,10 +10556,7 @@ static const struct inode_operations btrfs_dir_inode_operations = {
 	.symlink	= btrfs_symlink,
 	.setattr	= btrfs_setattr,
 	.mknod		= btrfs_mknod,
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr	= btrfs_listxattr,
-	.removexattr	= generic_removexattr,
 	.permission	= btrfs_permission,
 	.get_acl	= btrfs_get_acl,
 	.set_acl	= btrfs_set_acl,
@@ -10633,10 +10630,7 @@ static const struct address_space_operations btrfs_symlink_aops = {
 static const struct inode_operations btrfs_file_inode_operations = {
 	.getattr	= btrfs_getattr,
 	.setattr	= btrfs_setattr,
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr      = btrfs_listxattr,
-	.removexattr	= generic_removexattr,
 	.permission	= btrfs_permission,
 	.fiemap		= btrfs_fiemap,
 	.get_acl	= btrfs_get_acl,
@@ -10647,10 +10641,7 @@ static const struct inode_operations btrfs_special_inode_operations = {
 	.getattr	= btrfs_getattr,
 	.setattr	= btrfs_setattr,
 	.permission	= btrfs_permission,
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr	= btrfs_listxattr,
-	.removexattr	= generic_removexattr,
 	.get_acl	= btrfs_get_acl,
 	.set_acl	= btrfs_set_acl,
 	.update_time	= btrfs_update_time,
@@ -10661,10 +10652,7 @@ static const struct inode_operations btrfs_symlink_inode_operations = {
 	.getattr	= btrfs_getattr,
 	.setattr	= btrfs_setattr,
 	.permission	= btrfs_permission,
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr	= btrfs_listxattr,
-	.removexattr	= generic_removexattr,
 	.update_time	= btrfs_update_time,
 };
 
diff --git a/fs/cachefiles/bind.c b/fs/cachefiles/bind.c
index 6af790fc3df8..3ff867f87d73 100644
--- a/fs/cachefiles/bind.c
+++ b/fs/cachefiles/bind.c
@@ -20,6 +20,7 @@
 #include <linux/mount.h>
 #include <linux/statfs.h>
 #include <linux/ctype.h>
+#include <linux/xattr.h>
 #include "internal.h"
 
 static int cachefiles_daemon_add_cache(struct cachefiles_cache *caches);
@@ -126,8 +127,7 @@ static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache)
 	if (d_is_negative(root) ||
 	    !d_backing_inode(root)->i_op->lookup ||
 	    !d_backing_inode(root)->i_op->mkdir ||
-	    !d_backing_inode(root)->i_op->setxattr ||
-	    !d_backing_inode(root)->i_op->getxattr ||
+	    !(d_backing_inode(root)->i_opflags & IOP_XATTR) ||
 	    !root->d_sb->s_op->statfs ||
 	    !root->d_sb->s_op->sync_fs)
 		goto error_unsupported;
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index c6ee4b5fb7e6..339c910da916 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -20,6 +20,7 @@
 #include <linux/namei.h>
 #include <linux/security.h>
 #include <linux/slab.h>
+#include <linux/xattr.h>
 #include "internal.h"
 
 #define CACHEFILES_KEYBUF_SIZE 512
@@ -799,8 +800,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
 	}
 
 	ret = -EPERM;
-	if (!d_backing_inode(subdir)->i_op->setxattr ||
-	    !d_backing_inode(subdir)->i_op->getxattr ||
+	if (!(d_backing_inode(subdir)->i_opflags & IOP_XATTR) ||
 	    !d_backing_inode(subdir)->i_op->lookup ||
 	    !d_backing_inode(subdir)->i_op->mkdir ||
 	    !d_backing_inode(subdir)->i_op->create ||
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index df4b3e6fa563..e33bd0933396 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -1486,10 +1486,7 @@ const struct inode_operations ceph_dir_iops = {
 	.permission = ceph_permission,
 	.getattr = ceph_getattr,
 	.setattr = ceph_setattr,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
 	.listxattr = ceph_listxattr,
-	.removexattr = generic_removexattr,
 	.get_acl = ceph_get_acl,
 	.set_acl = ceph_set_acl,
 	.mknod = ceph_mknod,
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 082e82dcbaa4..da00b11d4a7a 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -94,10 +94,7 @@ const struct inode_operations ceph_file_iops = {
 	.permission = ceph_permission,
 	.setattr = ceph_setattr,
 	.getattr = ceph_getattr,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
 	.listxattr = ceph_listxattr,
-	.removexattr = generic_removexattr,
 	.get_acl = ceph_get_acl,
 	.set_acl = ceph_set_acl,
 };
@@ -1885,10 +1882,7 @@ static const struct inode_operations ceph_symlink_iops = {
 	.get_link = simple_get_link,
 	.setattr = ceph_setattr,
 	.getattr = ceph_getattr,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
 	.listxattr = ceph_listxattr,
-	.removexattr = generic_removexattr,
 };
 
 int __ceph_setattr(struct inode *inode, struct iattr *attr)
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 14ae4b8e1a3c..34aac1c73ee1 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -901,30 +901,21 @@ const struct inode_operations cifs_dir_inode_ops = {
 	.setattr = cifs_setattr,
 	.symlink = cifs_symlink,
 	.mknod   = cifs_mknod,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
 	.listxattr = cifs_listxattr,
-	.removexattr = generic_removexattr,
 };
 
 const struct inode_operations cifs_file_inode_ops = {
 	.setattr = cifs_setattr,
 	.getattr = cifs_getattr,
 	.permission = cifs_permission,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
 	.listxattr = cifs_listxattr,
-	.removexattr = generic_removexattr,
 };
 
 const struct inode_operations cifs_symlink_inode_ops = {
 	.readlink = generic_readlink,
 	.get_link = cifs_get_link,
 	.permission = cifs_permission,
-	.setxattr = generic_setxattr,
-	.getxattr = generic_getxattr,
 	.listxattr = cifs_listxattr,
-	.removexattr = generic_removexattr,
 };
 
 static int cifs_clone_file_range(struct file *src_file, loff_t off,
diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 4ba1547bb9ad..599a29237cfe 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -715,4 +715,6 @@ int ecryptfs_set_f_namelen(long *namelen, long lower_namelen,
 int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
 		       loff_t offset);
 
+extern const struct xattr_handler *ecryptfs_xattr_handlers[];
+
 #endif /* #ifndef ECRYPTFS_KERNEL_H */
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 5ffba186f352..ddccec3124d7 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -1005,15 +1005,14 @@ ecryptfs_setxattr(struct dentry *dentry, struct inode *inode,
 		  const char *name, const void *value,
 		  size_t size, int flags)
 {
-	int rc = 0;
+	int rc;
 	struct dentry *lower_dentry;
 
 	lower_dentry = ecryptfs_dentry_to_lower(dentry);
-	if (!d_inode(lower_dentry)->i_op->setxattr) {
+	if (!(d_inode(lower_dentry)->i_opflags & IOP_XATTR)) {
 		rc = -EOPNOTSUPP;
 		goto out;
 	}
-
 	rc = vfs_setxattr(lower_dentry, name, value, size, flags);
 	if (!rc && inode)
 		fsstack_copy_attr_all(inode, d_inode(lower_dentry));
@@ -1025,15 +1024,14 @@ ssize_t
 ecryptfs_getxattr_lower(struct dentry *lower_dentry, struct inode *lower_inode,
 			const char *name, void *value, size_t size)
 {
-	int rc = 0;
+	int rc;
 
-	if (!lower_inode->i_op->getxattr) {
+	if (!(lower_inode->i_opflags & IOP_XATTR)) {
 		rc = -EOPNOTSUPP;
 		goto out;
 	}
 	inode_lock(lower_inode);
-	rc = lower_inode->i_op->getxattr(lower_dentry, lower_inode,
-					 name, value, size);
+	rc = __vfs_getxattr(lower_dentry, lower_inode, name, value, size);
 	inode_unlock(lower_inode);
 out:
 	return rc;
@@ -1066,19 +1064,22 @@ out:
 	return rc;
 }
 
-static int ecryptfs_removexattr(struct dentry *dentry, const char *name)
+static int ecryptfs_removexattr(struct dentry *dentry, struct inode *inode,
+				const char *name)
 {
-	int rc = 0;
+	int rc;
 	struct dentry *lower_dentry;
+	struct inode *lower_inode;
 
 	lower_dentry = ecryptfs_dentry_to_lower(dentry);
-	if (!d_inode(lower_dentry)->i_op->removexattr) {
+	lower_inode = ecryptfs_inode_to_lower(inode);
+	if (!(lower_inode->i_opflags & IOP_XATTR)) {
 		rc = -EOPNOTSUPP;
 		goto out;
 	}
-	inode_lock(d_inode(lower_dentry));
-	rc = d_inode(lower_dentry)->i_op->removexattr(lower_dentry, name);
-	inode_unlock(d_inode(lower_dentry));
+	inode_lock(lower_inode);
+	rc = __vfs_removexattr(lower_dentry, name);
+	inode_unlock(lower_inode);
 out:
 	return rc;
 }
@@ -1089,10 +1090,7 @@ const struct inode_operations ecryptfs_symlink_iops = {
 	.permission = ecryptfs_permission,
 	.setattr = ecryptfs_setattr,
 	.getattr = ecryptfs_getattr_link,
-	.setxattr = ecryptfs_setxattr,
-	.getxattr = ecryptfs_getxattr,
 	.listxattr = ecryptfs_listxattr,
-	.removexattr = ecryptfs_removexattr
 };
 
 const struct inode_operations ecryptfs_dir_iops = {
@@ -1107,18 +1105,43 @@ const struct inode_operations ecryptfs_dir_iops = {
 	.rename = ecryptfs_rename,
 	.permission = ecryptfs_permission,
 	.setattr = ecryptfs_setattr,
-	.setxattr = ecryptfs_setxattr,
-	.getxattr = ecryptfs_getxattr,
 	.listxattr = ecryptfs_listxattr,
-	.removexattr = ecryptfs_removexattr
 };
 
 const struct inode_operations ecryptfs_main_iops = {
 	.permission = ecryptfs_permission,
 	.setattr = ecryptfs_setattr,
 	.getattr = ecryptfs_getattr,
-	.setxattr = ecryptfs_setxattr,
-	.getxattr = ecryptfs_getxattr,
 	.listxattr = ecryptfs_listxattr,
-	.removexattr = ecryptfs_removexattr
+};
+
+static int ecryptfs_xattr_get(const struct xattr_handler *handler,
+			      struct dentry *dentry, struct inode *inode,
+			      const char *name, void *buffer, size_t size)
+{
+	return ecryptfs_getxattr(dentry, inode, name, buffer, size);
+}
+
+static int ecryptfs_xattr_set(const struct xattr_handler *handler,
+			      struct dentry *dentry, struct inode *inode,
+			      const char *name, const void *value, size_t size,
+			      int flags)
+{
+	if (value)
+		return ecryptfs_setxattr(dentry, inode, name, value, size, flags);
+	else {
+		BUG_ON(flags != XATTR_REPLACE);
+		return ecryptfs_removexattr(dentry, inode, name);
+	}
+}
+
+const struct xattr_handler ecryptfs_xattr_handler = {
+	.prefix = "",  /* match anything */
+	.get = ecryptfs_xattr_get,
+	.set = ecryptfs_xattr_set,
+};
+
+const struct xattr_handler *ecryptfs_xattr_handlers[] = {
+	&ecryptfs_xattr_handler,
+	NULL
 };
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 612004495141..151872dcc1f4 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -529,6 +529,7 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
 	/* ->kill_sb() will take care of sbi after that point */
 	sbi = NULL;
 	s->s_op = &ecryptfs_sops;
+	s->s_xattr = ecryptfs_xattr_handlers;
 	s->s_d_op = &ecryptfs_dops;
 
 	err = "Reading sb failed";
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 9c3437c8a5b1..1f0c471b4ba3 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -32,6 +32,7 @@
 #include <linux/file.h>
 #include <linux/scatterlist.h>
 #include <linux/slab.h>
+#include <linux/xattr.h>
 #include <asm/unaligned.h>
 #include "ecryptfs_kernel.h"
 
@@ -422,7 +423,7 @@ static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 	struct inode *lower_inode = d_inode(lower_dentry);
 	int rc;
 
-	if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
+	if (!(lower_inode->i_opflags & IOP_XATTR)) {
 		printk(KERN_WARNING
 		       "No support for setting xattr in lower filesystem\n");
 		rc = -ENOSYS;
@@ -436,15 +437,13 @@ static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 		goto out;
 	}
 	inode_lock(lower_inode);
-	size = lower_inode->i_op->getxattr(lower_dentry, lower_inode,
-					   ECRYPTFS_XATTR_NAME,
-					   xattr_virt, PAGE_SIZE);
+	size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
+			      xattr_virt, PAGE_SIZE);
 	if (size < 0)
 		size = 8;
 	put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
-	rc = lower_inode->i_op->setxattr(lower_dentry, lower_inode,
-					 ECRYPTFS_XATTR_NAME,
-					 xattr_virt, size, 0);
+	rc = __vfs_setxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
+			    xattr_virt, size, 0);
 	inode_unlock(lower_inode);
 	if (rc)
 		printk(KERN_ERR "Error whilst attempting to write inode size "
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 0ca363d1341c..a0e1478dfd04 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -241,10 +241,7 @@ const struct file_operations ext2_file_operations = {
 
 const struct inode_operations ext2_file_inode_operations = {
 #ifdef CONFIG_EXT2_FS_XATTR
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr	= ext2_listxattr,
-	.removexattr	= generic_removexattr,
 #endif
 	.setattr	= ext2_setattr,
 	.get_acl	= ext2_get_acl,
diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index d446203127fc..ff32ea799496 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -428,10 +428,7 @@ const struct inode_operations ext2_dir_inode_operations = {
 	.mknod		= ext2_mknod,
 	.rename		= ext2_rename,
 #ifdef CONFIG_EXT2_FS_XATTR
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr	= ext2_listxattr,
-	.removexattr	= generic_removexattr,
 #endif
 	.setattr	= ext2_setattr,
 	.get_acl	= ext2_get_acl,
@@ -441,10 +438,7 @@ const struct inode_operations ext2_dir_inode_operations = {
 
 const struct inode_operations ext2_special_inode_operations = {
 #ifdef CONFIG_EXT2_FS_XATTR
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr	= ext2_listxattr,
-	.removexattr	= generic_removexattr,
 #endif
 	.setattr	= ext2_setattr,
 	.get_acl	= ext2_get_acl,
diff --git a/fs/ext2/symlink.c b/fs/ext2/symlink.c
index 3495d8ae4b33..8437b191bf5d 100644
--- a/fs/ext2/symlink.c
+++ b/fs/ext2/symlink.c
@@ -25,10 +25,7 @@ const struct inode_operations ext2_symlink_inode_operations = {
 	.get_link	= page_get_link,
 	.setattr	= ext2_setattr,
 #ifdef CONFIG_EXT2_FS_XATTR
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr	= ext2_listxattr,
-	.removexattr	= generic_removexattr,
 #endif
 };
  
@@ -37,9 +34,6 @@ const struct inode_operations ext2_fast_symlink_inode_operations = {
 	.get_link	= simple_get_link,
 	.setattr	= ext2_setattr,
 #ifdef CONFIG_EXT2_FS_XATTR
-	.setxattr	= generic_setxattr,
-	.getxattr	= generic_getxattr,
 	.listxattr	= ext2_listxattr,
-	.removexattr	= generic_removexattr,
 #endif
 };
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 36d49cfbf2dc..2a822d30e73f 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -706,10 +706,7 @@ const struct file_operations ext4_file_operati