linux/vfsops: remove zfs_mnt_t, pass directly

A cleanup of opportunity. Since we already are modifying the contents of
zfs_mnt_t, we've broken any API guarantee, so we might as well go the
rest of the way and get rid of it, and just pass the osname and/or the
vfs_t directly.

It seems like zfs_mnt_t was never really needed anyway; it was added in
1c2555ef92 (March 2017) to minimise the difference to illumos, but
zfs_vfsops was made platform-specific anyway in 7b4e27232d.

We also remove setting SB_RDONLY on the caller's flags when failing a
read-write remount on a read-only snapshot or pool. Since 0f608aa6ca
the caller's flags have been a pointer back to fc->sb_flags, which are
discarded without further ceremony when the operation fails, so the
change is unnecessary and we can simplify the call further.

Sponsored-by: TrueNAS
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@truenas.com>
Closes #18377

include/os/linux/zfs/sys/zfs_vfsops_os.h

@@ -74,11 +74,6 @@ typedef struct vfs {
 	kmutex_t	vfs_mntpt_lock;
 } vfs_t;
 
-typedef struct zfs_mnt {
-	const char	*mnt_osname;	/* Objset name */
-	vfs_t		*mnt_opts;	/* Parsed options */
-} zfs_mnt_t;
-
 struct zfsvfs {
 	vfs_t		*z_vfs;		/* generic fs struct */
 	struct super_block *z_sb;	/* generic super_block */
@@ -250,10 +245,11 @@ extern vfs_t *zfsvfs_vfs_alloc(void);
 extern void zfsvfs_vfs_free(vfs_t *vfsp);
 
 extern boolean_t zfs_is_readonly(zfsvfs_t *zfsvfs);
-extern int zfs_domount(struct super_block *sb, zfs_mnt_t *zm, int silent);
+extern int zfs_domount(struct super_block *sb, const char *osname,
+    vfs_t *mntopts, int silent);
 extern void zfs_preumount(struct super_block *sb);
 extern int zfs_umount(struct super_block *sb);
-extern int zfs_remount(struct super_block *sb, int *flags, zfs_mnt_t *zm);
+extern int zfs_remount(struct super_block *sb, vfs_t *mntopts, int flags);
 extern int zfs_statvfs(struct inode *ip, struct kstatfs *statp);
 extern int zfs_vget(struct super_block *sb, struct inode **ipp, fid_t *fidp);
 extern int zfs_prune(struct super_block *sb, unsigned long nr_to_scan,

module/os/linux/zfs/zfs_vfsops.c

@@ -1316,20 +1316,16 @@ zfsvfs_teardown(zfsvfs_t *zfsvfs, boolean_t unmounting)
 static atomic_long_t zfs_bdi_seq = ATOMIC_LONG_INIT(0);
 
 int
-zfs_domount(struct super_block *sb, zfs_mnt_t *zm, int silent)
+zfs_domount(struct super_block *sb, const char *osname,
+    vfs_t *vfs, int silent)
 {
-	const char *osname = zm->mnt_osname;
 	struct inode *root_inode = NULL;
 	uint64_t recordsize;
 	int error = 0;
 	zfsvfs_t *zfsvfs = NULL;
-	vfs_t *vfs = zm->mnt_opts;
 	int canwrite;
 	int dataset_visible_zone;
 
-	ASSERT(zm);
-	ASSERT(osname);
-
 	dataset_visible_zone = zone_dataset_visible(osname, &canwrite);
 
 	/*
@@ -1533,19 +1529,16 @@ zfs_umount(struct super_block *sb)
 }
 
 int
-zfs_remount(struct super_block *sb, int *flags, zfs_mnt_t *zm)
+zfs_remount(struct super_block *sb, vfs_t *vfsp, int flags)
 {
 	zfsvfs_t *zfsvfs = sb->s_fs_info;
-	vfs_t *vfsp = zm->mnt_opts;
 	boolean_t issnap = dmu_objset_is_snapshot(zfsvfs->z_os);
 
 	if ((issnap || !spa_writeable(dmu_objset_spa(zfsvfs->z_os))) &&
-	    !(*flags & SB_RDONLY)) {
+	    !(flags & SB_RDONLY))
-		*flags |= SB_RDONLY;
 		return (EROFS);
-	}
 
-	if (!zfs_is_readonly(zfsvfs) && (*flags & SB_RDONLY))
+	if (!zfs_is_readonly(zfsvfs) && (flags & SB_RDONLY))
 		txg_wait_synced(dmu_objset_pool(zfsvfs->z_os), 0);
 
 	zfs_unregister_callbacks(zfsvfs);

module/os/linux/zfs/zpl_super.c

@@ -880,13 +880,9 @@ zpl_get_tree(struct fs_context *fc)
 			vfs->vfs_do_readonly = B_TRUE;
 		}
 
-		zfs_mnt_t zm = {
-		    .mnt_osname = fc->source,
-		    .mnt_opts = vfs,
-		};
-
 		fstrans_cookie_t cookie = spl_fstrans_mark();
-		err = zfs_domount(sb, &zm, fc->sb_flags & SB_SILENT ? 1 : 0);
+		err = zfs_domount(sb, fc->source, vfs,
+		    fc->sb_flags & SB_SILENT ? 1 : 0);
 		spl_fstrans_unmark(cookie);
 
 		if (err) {
@@ -921,12 +917,11 @@ zpl_get_tree(struct fs_context *fc)
 static int
 zpl_reconfigure(struct fs_context *fc)
 {
-	zfs_mnt_t zm = { .mnt_osname = NULL, .mnt_opts = fc->fs_private };
 	fstrans_cookie_t cookie;
 	int error;
 
 	cookie = spl_fstrans_mark();
-	error = -zfs_remount(fc->root->d_sb, &fc->sb_flags, &zm);
+	error = -zfs_remount(fc->root->d_sb, fc->fs_private, fc->sb_flags);
 	spl_fstrans_unmark(cookie);
 	ASSERT3S(error, <=, 0);