[RFC PATCH 51/68] vfs: Convert squashfs to use the new mount API

[David Howells]

Convert the squashfs filesystem to the new internal mount API as the old
one will be obsoleted and removed.  This allows greater flexibility in
communication of mount parameters between userspace, the VFS and the
filesystem.

See Documentation/filesystems/mount_api.txt for more information.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Phillip Lougher <phillip@xxxxxxxxxxxxxxx>
cc: squashfs-devel@xxxxxxxxxxxxxxxxxxxxx
---

 fs/squashfs/super.c |  100 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 55 insertions(+), 45 deletions(-)

diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 40e657386fa5..672011725eb2 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -30,6 +30,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/fs.h>
+#include <linux/fs_context.h>
 #include <linux/vfs.h>
 #include <linux/slab.h>
 #include <linux/mutex.h>
@@ -49,26 +50,27 @@
 static struct file_system_type squashfs_fs_type;
 static const struct super_operations squashfs_super_ops;
 
-static const struct squashfs_decompressor *supported_squashfs_filesystem(short
-	major, short minor, short id)
+static const struct squashfs_decompressor *supported_squashfs_filesystem(
+	struct fs_context *fc,
+	short major, short minor, short id)
 {
 	const struct squashfs_decompressor *decompressor;
 
 	if (major < SQUASHFS_MAJOR) {
-		ERROR("Major/Minor mismatch, older Squashfs %d.%d "
-			"filesystems are unsupported\n", major, minor);
+		errorf(fc, "Major/Minor mismatch, older Squashfs %d.%d "
+		       "filesystems are unsupported", major, minor);
 		return NULL;
 	} else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
-		ERROR("Major/Minor mismatch, trying to mount newer "
-			"%d.%d filesystem\n", major, minor);
-		ERROR("Please update your kernel\n");
+		errorf(fc, "Major/Minor mismatch, trying to mount newer "
+		       "%d.%d filesystem", major, minor);
+		errorf(fc, "Please update your kernel");
 		return NULL;
 	}
 
 	decompressor = squashfs_lookup_decompressor(id);
 	if (!decompressor->supported) {
-		ERROR("Filesystem uses \"%s\" compression. This is not "
-			"supported\n", decompressor->name);
+		errorf(fc, "Filesystem uses \"%s\" compression. This is not supported",
+		       decompressor->name);
 		return NULL;
 	}
 
@@ -76,7 +78,7 @@ static const struct squashfs_decompressor *supported_squashfs_filesystem(short
 }
 
 
-static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
+static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct squashfs_sb_info *msblk;
 	struct squashfs_super_block *sblk = NULL;
@@ -111,7 +113,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));
 
 	if (IS_ERR(sblk)) {
-		ERROR("unable to read squashfs_super_block\n");
+		errorf(fc, "unable to read squashfs_super_block");
 		err = PTR_ERR(sblk);
 		sblk = NULL;
 		goto failed_mount;
@@ -122,14 +124,15 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	/* Check it is a SQUASHFS superblock */
 	sb->s_magic = le32_to_cpu(sblk->s_magic);
 	if (sb->s_magic != SQUASHFS_MAGIC) {
-		if (!silent)
-			ERROR("Can't find a SQUASHFS superblock on %pg\n",
-						sb->s_bdev);
+		if (!(fc->sb_flags & SB_SILENT))
+			errorf(fc, "Can't find a SQUASHFS superblock on %pg",
+			       sb->s_bdev);
 		goto failed_mount;
 	}
 
 	/* Check the MAJOR & MINOR versions and lookup compression type */
 	msblk->decompressor = supported_squashfs_filesystem(
+			fc,
 			le16_to_cpu(sblk->s_major),
 			le16_to_cpu(sblk->s_minor),
 			le16_to_cpu(sblk->compression));
@@ -146,15 +149,15 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	/* Check block size for sanity */
 	msblk->block_size = le32_to_cpu(sblk->block_size);
 	if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
-		goto failed_mount;
+		goto insanity;
 
 	/*
 	 * Check the system page size is not larger than the filesystem
 	 * block size (by default 128K).  This is currently not supported.
 	 */
 	if (PAGE_SIZE > msblk->block_size) {
-		ERROR("Page size > filesystem block size (%d).  This is "
-			"currently not supported!\n", msblk->block_size);
+		errorf(fc, "Page size > filesystem block size (%d).  This is "
+		       "currently not supported!", msblk->block_size);
 		goto failed_mount;
 	}
 
@@ -165,12 +168,12 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 
 	/* Check that block_size and block_log match */
 	if (msblk->block_size != (1 << msblk->block_log))
-		goto failed_mount;
+		goto insanity;
 
 	/* Check the root inode for sanity */
 	root_inode = le64_to_cpu(sblk->root_inode);
 	if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
-		goto failed_mount;
+		goto insanity;
 
 	msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
 	msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
@@ -210,7 +213,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	msblk->read_page = squashfs_cache_init("data",
 		squashfs_max_decompressors(), msblk->block_size);
 	if (msblk->read_page == NULL) {
-		ERROR("Failed to allocate read_page block\n");
+		errorf(fc, "Failed to allocate read_page block");
 		goto failed_mount;
 	}
 
@@ -218,7 +221,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	if (IS_ERR(msblk->stream)) {
 		err = PTR_ERR(msblk->stream);
 		msblk->stream = NULL;
-		goto failed_mount;
+		goto insanity;
 	}
 
 	/* Handle xattrs */
@@ -233,7 +236,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
 		xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
 	if (IS_ERR(msblk->xattr_id_table)) {
-		ERROR("unable to read xattr id index table\n");
+		errorf(fc, "unable to read xattr id index table");
 		err = PTR_ERR(msblk->xattr_id_table);
 		msblk->xattr_id_table = NULL;
 		if (err != -ENOTSUPP)
@@ -247,7 +250,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 		le64_to_cpu(sblk->id_table_start), next_table,
 		le16_to_cpu(sblk->no_ids));
 	if (IS_ERR(msblk->id_table)) {
-		ERROR("unable to read id index table\n");
+		errorf(fc, "unable to read id index table");
 		err = PTR_ERR(msblk->id_table);
 		msblk->id_table = NULL;
 		goto failed_mount;
@@ -263,7 +266,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
 		lookup_table_start, next_table, msblk->inodes);
 	if (IS_ERR(msblk->inode_lookup_table)) {
-		ERROR("unable to read inode lookup table\n");
+		errorf(fc, "unable to read inode lookup table");
 		err = PTR_ERR(msblk->inode_lookup_table);
 		msblk->inode_lookup_table = NULL;
 		goto failed_mount;
@@ -288,7 +291,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	msblk->fragment_index = squashfs_read_fragment_index_table(sb,
 		le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
 	if (IS_ERR(msblk->fragment_index)) {
-		ERROR("unable to read fragment index table\n");
+		errorf(fc, "unable to read fragment index table");
 		err = PTR_ERR(msblk->fragment_index);
 		msblk->fragment_index = NULL;
 		goto failed_mount;
@@ -299,13 +302,13 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	/* Sanity check directory_table */
 	if (msblk->directory_table > next_table) {
 		err = -EINVAL;
-		goto failed_mount;
+		goto insanity;
 	}
 
 	/* Sanity check inode_table */
 	if (msblk->inode_table >= msblk->directory_table) {
 		err = -EINVAL;
-		goto failed_mount;
+		goto insanity;
 	}
 
 	/* allocate root */
@@ -334,6 +337,8 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	kfree(sblk);
 	return 0;
 
+insanity:
+	errorf(fc, "squashfs image failed sanity check");
 failed_mount:
 	squashfs_cache_delete(msblk->block_cache);
 	squashfs_cache_delete(msblk->fragment_cache);
@@ -349,6 +354,28 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	return err;
 }
 
+static int squashfs_get_tree(struct fs_context *fc)
+{
+	return vfs_get_block_super(fc, squashfs_fill_super);
+}
+
+static int squashfs_reconfigure(struct fs_context *fc)
+{
+	sync_filesystem(fc->root->d_sb);
+	fc->sb_flags |= SB_RDONLY;
+	return 0;
+}
+
+static const struct fs_context_operations squashfs_context_ops = {
+	.get_tree	= squashfs_get_tree,
+	.reconfigure	= squashfs_reconfigure,
+};
+
+static int squashfs_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &squashfs_context_ops;
+	return 0;
+}
 
 static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
@@ -371,14 +398,6 @@ static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 }
 
 
-static int squashfs_remount(struct super_block *sb, int *flags, char *data)
-{
-	sync_filesystem(sb);
-	*flags |= SB_RDONLY;
-	return 0;
-}
-
-
 static void squashfs_put_super(struct super_block *sb)
 {
 	if (sb->s_fs_info) {
@@ -397,14 +416,6 @@ static void squashfs_put_super(struct super_block *sb)
 	}
 }
 
-
-static struct dentry *squashfs_mount(struct file_system_type *fs_type,
-				int flags, const char *dev_name, void *data)
-{
-	return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
-}
-
-
 static struct kmem_cache *squashfs_inode_cachep;
 
 
@@ -488,7 +499,7 @@ static void squashfs_destroy_inode(struct inode *inode)
 static struct file_system_type squashfs_fs_type = {
 	.owner = THIS_MODULE,
 	.name = "squashfs",
-	.mount = squashfs_mount,
+	.init_fs_context = squashfs_init_fs_context,
 	.kill_sb = kill_block_super,
 	.fs_flags = FS_REQUIRES_DEV
 };
@@ -499,7 +510,6 @@ static const struct super_operations squashfs_super_ops = {
 	.destroy_inode = squashfs_destroy_inode,
 	.statfs = squashfs_statfs,
 	.put_super = squashfs_put_super,
-	.remount_fs = squashfs_remount
 };
 
 module_init(init_squashfs_fs);