Linux 4.11 compat: iops.getattr and friends

In torvalds/linux@a528d35, there are changes to the getattr family of functions,
struct kstat, and the interface of inode_operations .getattr.

The inode_operations .getattr and simple_getattr() interface changed to:

int (*getattr) (const struct path *, struct dentry *, struct kstat *,
    u32 request_mask, unsigned int query_flags)

The request_mask argument indicates which field(s) the caller intends to use.
Fields the caller has not specified via request_mask may be set in the returned
struct anyway, but their values may be approximate.

The query_flags argument indicates whether the filesystem must update
the attributes from the backing store.

Currently both fields are ignored.  It is possible that getattr-related
functions within zfs could be optimized based on the request_mask.

struct kstat includes new fields:
u32               result_mask;  /* What fields the user got */
u64               attributes;   /* See STATX_ATTR_* flags */
struct timespec   btime;        /* File creation time */

Fields attribute and btime are cleared; the result_mask reflects this.  These
appear to be optional based on simple_getattr() and vfs_getattr() within the
kernel, which take the same approach.

Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #5875

module/zfs/zpl_ctldir.c

@@ -100,16 +100,15 @@ zpl_root_readdir(struct file *filp, void *dirent, filldir_t filldir)
  */
 /* ARGSUSED */
 static int
-zpl_root_getattr(struct vfsmount *mnt, struct dentry *dentry,
-    struct kstat *stat)
+zpl_root_getattr_impl(const struct path *path, struct kstat *stat,
+    u32 request_mask, unsigned int query_flags)
 {
-	int error;
-
-	error = simple_getattr(mnt, dentry, stat);
+	generic_fillattr(path->dentry->d_inode, stat);
 	stat->atime = CURRENT_TIME;
 
-	return (error);
+	return (0);
 }
+ZPL_GETATTR_WRAPPER(zpl_root_getattr);
 
 static struct dentry *
 #ifdef HAVE_LOOKUP_NAMEIDATA
@@ -375,21 +374,22 @@ zpl_snapdir_mkdir(struct inode *dip, struct dentry *dentry, zpl_umode_t mode)
  */
 /* ARGSUSED */
 static int
-zpl_snapdir_getattr(struct vfsmount *mnt, struct dentry *dentry,
-    struct kstat *stat)
+zpl_snapdir_getattr_impl(const struct path *path, struct kstat *stat,
+    u32 request_mask, unsigned int query_flags)
 {
-	zfsvfs_t *zfsvfs = ITOZSB(dentry->d_inode);
-	int error;
+	zfsvfs_t *zfsvfs = ITOZSB(path->dentry->d_inode);
 
 	ZFS_ENTER(zfsvfs);
-	error = simple_getattr(mnt, dentry, stat);
+	generic_fillattr(path->dentry->d_inode, stat);
+
 	stat->nlink = stat->size = 2;
 	stat->ctime = stat->mtime = dmu_objset_snap_cmtime(zfsvfs->z_os);
 	stat->atime = CURRENT_TIME;
 	ZFS_EXIT(zfsvfs);
 
-	return (error);
+	return (0);
 }
+ZPL_GETATTR_WRAPPER(zpl_snapdir_getattr);
 
 /*
  * The '.zfs/snapshot' directory file operations.  These mainly control
@@ -509,10 +509,10 @@ zpl_shares_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
 /* ARGSUSED */
 static int
-zpl_shares_getattr(struct vfsmount *mnt, struct dentry *dentry,
-    struct kstat *stat)
+zpl_shares_getattr_impl(const struct path *path, struct kstat *stat,
+    u32 request_mask, unsigned int query_flags)
 {
-	struct inode *ip = dentry->d_inode;
+	struct inode *ip = path->dentry->d_inode;
 	zfsvfs_t *zfsvfs = ITOZSB(ip);
 	znode_t *dzp;
 	int error;
@@ -520,11 +520,11 @@ zpl_shares_getattr(struct vfsmount *mnt, struct dentry *dentry,
 	ZFS_ENTER(zfsvfs);
 
 	if (zfsvfs->z_shares_dir == 0) {
-		error = simple_getattr(mnt, dentry, stat);
+		generic_fillattr(path->dentry->d_inode, stat);
 		stat->nlink = stat->size = 2;
 		stat->atime = CURRENT_TIME;
 		ZFS_EXIT(zfsvfs);
-		return (error);
+		return (0);
 	}
 
 	error = -zfs_zget(zfsvfs, zfsvfs->z_shares_dir, &dzp);
@@ -538,6 +538,7 @@ zpl_shares_getattr(struct vfsmount *mnt, struct dentry *dentry,
 
 	return (error);
 }
+ZPL_GETATTR_WRAPPER(zpl_shares_getattr);
 
 /*
  * The '.zfs/shares' directory file operations.

module/zfs/zpl_inode.c

@@ -340,18 +340,25 @@ zpl_rmdir(struct inode *dir, struct dentry *dentry)
 }
 
 static int
-zpl_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+zpl_getattr_impl(const struct path *path, struct kstat *stat, u32 request_mask,
+    unsigned int query_flags)
 {
 	int error;
 	fstrans_cookie_t cookie;
 
 	cookie = spl_fstrans_mark();
-	error = -zfs_getattr_fast(dentry->d_inode, stat);
+
+	/*
+	 * XXX request_mask and query_flags currently ignored.
+	 */
+
+	error = -zfs_getattr_fast(path->dentry->d_inode, stat);
 	spl_fstrans_unmark(cookie);
 	ASSERT3S(error, <=, 0);
 
 	return (error);
 }
+ZPL_GETATTR_WRAPPER(zpl_getattr);
 
 static int
 zpl_setattr(struct dentry *dentry, struct iattr *ia)