fs: push sync_filesystem() down to the file system's remount_fs()

Previously, the no-op "mount -o mount /dev/xxx" operation when the
file system is already mounted read-write causes an implied,
unconditional syncfs().  This seems pretty stupid, and it's certainly
documented or guaraunteed to do this, nor is it particularly useful,
except in the case where the file system was mounted rw and is getting
remounted read-only.

However, it's possible that there might be some file systems that are
actually depending on this behavior.  In most file systems, it's
probably fine to only call sync_filesystem() when transitioning from
read-write to read-only, and there are some file systems where this is
not needed at all (for example, for a pseudo-filesystem or something
like romfs).

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Jan Kara <jack@suse.cz>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Anders Larsen <al@alarsen.net>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: Petr Vandrovec <petr@vandrovec.name>
Cc: xfs@oss.sgi.com
Cc: linux-btrfs@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: codalist@coda.cs.cmu.edu
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: fuse-devel@lists.sourceforge.net
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: linux-nilfs@vger.kernel.org
Cc: linux-ntfs-dev@lists.sourceforge.net
Cc: ocfs2-devel@oss.oracle.com
Cc: reiserfs-devel@vger.kernel.org

fs/adfs/super.c

@@ -212,6 +212,7 @@ static int parse_options(struct super_block *sb, char *options)
 
 static int adfs_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	*flags |= MS_NODIRATIME;
 	return parse_options(sb, data);
 }

fs/affs/super.c

@@ -530,6 +530,7 @@ affs_remount(struct super_block *sb, int *flags, char *data)
 
 	pr_debug("AFFS: remount(flags=0x%x,opts=\"%s\")\n",*flags,data);
 
+	sync_filesystem(sb);
 	*flags |= MS_NODIRATIME;
 
 	memcpy(volume, sbi->s_volume, 32);

fs/befs/linuxvfs.c

@@ -913,6 +913,7 @@ befs_fill_super(struct super_block *sb, void *data, int silent)
 static int
 befs_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	if (!(*flags & MS_RDONLY))
 		return -EINVAL;
 	return 0;

fs/btrfs/super.c

@@ -1381,6 +1381,7 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 	unsigned int old_metadata_ratio = fs_info->metadata_ratio;
 	int ret;
 
+	sync_filesystem(sb);
 	btrfs_remount_prepare(fs_info);
 
 	ret = btrfs_parse_options(root, data);

fs/cifs/cifsfs.c

@@ -541,6 +541,7 @@ static int cifs_show_stats(struct seq_file *s, struct dentry *root)
 
 static int cifs_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	*flags |= MS_NODIRATIME;
 	return 0;
 }

fs/coda/inode.c

@@ -96,6 +96,7 @@ void coda_destroy_inodecache(void)
 
 static int coda_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	*flags |= MS_NOATIME;
 	return 0;
 }

fs/cramfs/inode.c

@@ -244,6 +244,7 @@ static void cramfs_kill_sb(struct super_block *sb)
 
 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	*flags |= MS_RDONLY;
 	return 0;
 }

fs/debugfs/inode.c

@@ -218,6 +218,7 @@ static int debugfs_remount(struct super_block *sb, int *flags, char *data)
 	int err;
 	struct debugfs_fs_info *fsi = sb->s_fs_info;
 
+	sync_filesystem(sb);
 	err = debugfs_parse_options(data, &fsi->mount_opts);
 	if (err)
 		goto fail;

fs/devpts/inode.c

@@ -313,6 +313,7 @@ static int devpts_remount(struct super_block *sb, int *flags, char *data)
 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
 	struct pts_mount_opts *opts = &fsi->mount_opts;
 
+	sync_filesystem(sb);
 	err = parse_mount_options(data, PARSE_REMOUNT, opts);
 
 	/*

fs/efs/super.c

@@ -114,6 +114,7 @@ static void destroy_inodecache(void)
 
 static int efs_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	*flags |= MS_RDONLY;
 	return 0;
 }

fs/ext2/super.c

@@ -1254,6 +1254,7 @@ static int ext2_remount (struct super_block * sb, int * flags, char * data)
 	unsigned long old_sb_flags;
 	int err;
 
+	sync_filesystem(sb);
 	spin_lock(&sbi->s_lock);
 
 	/* Store the old options */

fs/ext3/super.c

@@ -2649,6 +2649,8 @@ static int ext3_remount (struct super_block * sb, int * flags, char * data)
 	int i;
 #endif
 
+	sync_filesystem(sb);
+
 	/* Store the original options */
 	old_sb_flags = sb->s_flags;
 	old_opts.s_mount_opt = sbi->s_mount_opt;

fs/ext4/super.c

@@ -4765,6 +4765,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 #endif
 	char *orig_data = kstrdup(data, GFP_KERNEL);
 
+	sync_filesystem(sb);
+
 	/* Store the original options */
 	old_sb_flags = sb->s_flags;
 	old_opts.s_mount_opt = sbi->s_mount_opt;

fs/f2fs/super.c

@@ -568,6 +568,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	struct f2fs_mount_info org_mount_opt;
 	int err, active_logs;
 
+	sync_filesystem(sb);
+
 	/*
 	 * Save the old mount options in case we
 	 * need to restore them.

fs/fat/inode.c

@@ -635,6 +635,8 @@ static int fat_remount(struct super_block *sb, int *flags, char *data)
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 	*flags |= MS_NODIRATIME | (sbi->options.isvfat ? 0 : MS_NOATIME);
 
+	sync_filesystem(sb);
+
 	/* make sure we update state on remount. */
 	new_rdonly = *flags & MS_RDONLY;
 	if (new_rdonly != (sb->s_flags & MS_RDONLY)) {

fs/freevxfs/vxfs_super.c

@@ -124,6 +124,7 @@ vxfs_statfs(struct dentry *dentry, struct kstatfs *bufp)
 
 static int vxfs_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	*flags |= MS_RDONLY;
 	return 0;
 }

fs/fuse/inode.c

@@ -135,6 +135,7 @@ static void fuse_evict_inode(struct inode *inode)
 
 static int fuse_remount_fs(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	if (*flags & MS_MANDLOCK)
 		return -EINVAL;
 

fs/gfs2/super.c

@@ -1175,6 +1175,8 @@ static int gfs2_remount_fs(struct super_block *sb, int *flags, char *data)
 	struct gfs2_tune *gt = &sdp->sd_tune;
 	int error;
 
+	sync_filesystem(sb);
+
 	spin_lock(&gt->gt_spin);
 	args.ar_commit = gt->gt_logd_secs;
 	args.ar_quota_quantum = gt->gt_quota_quantum;

fs/hfs/super.c

@@ -112,6 +112,7 @@ static int hfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 
 static int hfs_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	*flags |= MS_NODIRATIME;
 	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
 		return 0;

fs/hfsplus/super.c

@@ -323,6 +323,7 @@ static int hfsplus_statfs(struct dentry *dentry, struct kstatfs *buf)
 
 static int hfsplus_remount(struct super_block *sb, int *flags, char *data)
 {
+	sync_filesystem(sb);
 	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
 		return 0;
 	if (!(*flags & MS_RDONLY)) {