Re: [PATCH 1/2] f2fs: add remount_fs callback support

Re: [PATCH 1/2] f2fs: add remount_fs callback support

[Gu Zheng]

Hi Namjae,

On 06/05/2013 12:34 PM, Namjae Jeon wrote:

> 2013/6/4 Gu Zheng <guz.fnst@cn.fujitsu.com>:
>> On 06/01/2013 03:20 PM, Namjae Jeon wrote:
>>
>>> From: Namjae Jeon <namjae.jeon@samsung.com>
>>>
>>> Add the f2fs_remount function call which will be used
>>> during the filesystem remounting. This function
>>> will help us to change the mount options specific to
>>> f2fs.
>>>
>>> Also modify the f2fs background_gc mount option, which
>>> will allow the user to dynamically trun on/off the
>>> garbage collection in f2fs based on the background_gc
>>> value. If background_gc=0, Garbage collection will
>>> be turned off & if background_gc=1, Garbage collection
>>> will be truned on.
>>
>>
>> Hi Namjae,
> Hi. Gu.
> 
>>   I think splitting these two changes into single ones seems better.
>> Refer to the inline comments.
> I don't think so. Mount option background_gc is changed to make
> remount_fs working in the correct way.

Yes, I know. Maybe you somewhat misread my words. 
Though remount_fs is dependent on changing background_gc option, but the change of background_gc option
and the adding remount_fs support are two different changes.
In order to make each patch simple and clear, maybe you need to split into single ones,
such as:
[PATCH 1/3] f2fs: Modify the f2fs background_gc mount option
[PATCH 2/3] f2fs: add remount_fs callback support
[PATCH 3/3] f2fs: reorganise the function get_victim_by_default

Just a personal suggestion, if you think it is worthless, please ignore it.:)


> 
>>
>> Thanks,
>> Gu
>>
>>
>> Though simply option show is enough, but I think the "background_gc=on/off" is more friendly.
> Yes, Agree. I will update.
> 
>>
>>> +
>>> +     /**
>>> +      * We stop the GC thread if FS is mounted as RO
>>> +      * or if background_gc = 0 is passed in mount
>>> +      * option. Also sync the filesystem.
>>> +      */
>>> +     if ((*flags & MS_RDONLY) || !test_opt(sbi, BG_GC)) {
>>
>>
>> Another condition: The old mount is not RO.
> I don't think that it is needed. I think current condition check can
> be covered about all cases.
> Am I missing something ?

Maybe. If the old mount is RO, so does the remount. It still can pass the judgement here, right?
Though the following stop_gc_thread() and f2fs_sync_fs() can handle this case well, but this
is unnecessary and needless. If we add additional judgement of whether old mount is not RO can avoid this.

Thanks,
Gu

> 
>>
>>> +             stop_gc_thread(sbi);
>>> +             f2fs_sync_fs(sb, 1);
>>> +     } else if (test_opt(sbi, BG_GC) && !sbi->gc_thread) {
>>> +             err = start_gc_thread(sbi);
>>> +             if (err)
>>> +                     goto restore_opts;
>>> +     }
>>> +
>>> +     /* Update the POSIXACL Flag */
>>> +      sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
>>> +             (test_opt(sbi, POSIX_ACL) ? MS_POSIXACL : 0);
>>
>>
>> Maybe you forget to update the flags with MS_RDONLY or ~MS_RDONLY, if the flags changed.
> No, we don't need to check this flags. sb-s_flags will be updated by
> MS_REMOUNT of vfs.(do_remount_sb)
> 
>>
>>> +     return 0;
>>> +
>>> +restore_opts:
>>> +     sb->s_flags = old_sb_flags;
>>
>>
>> There is no need to restore sb->s_flags, parse_options() did not change it.
>> no need to store the old sb->s_flags too.
> Yes, right, I will update.
> 
>>
>>>
>>> -     /* After POR, we can run background GC thread */
>>> -     err = start_gc_thread(sbi);
>>> -     if (err)
>>> -             goto fail;
>>> +     /* After POR, we can run background GC thread.*/
>>> +     if (!(sb->s_flags & MS_RDONLY)) {
>>> +             /**
>>> +              * If filesystem is mounted as read-only then
>>> +              * do not start the gc_thread.
>>> +              */
>>
>> It seems that the comment here is against with the logic.
> hum.. Okay, I will update comment to avoid some confusion.
> 
> Thanks for review :)
> I will post v2 patch including your opinion soon.
> 

[PATCH 1/2] f2fs: add remount_fs callback support

[Namjae Jeon]

From: Namjae Jeon <namjae.jeon@samsung.com>

Add the f2fs_remount function call which will be used
during the filesystem remounting. This function
will help us to change the mount options specific to
f2fs.

Also modify the f2fs background_gc mount option, which
will allow the user to dynamically trun on/off the
garbage collection in f2fs based on the background_gc
value. If background_gc=on, Garbage collection will
be turned off & if background_gc=off, Garbage collection
will be truned on.

By default the garbage collection is on in f2fs.

Change Log:
v2: Incorporated the review comments by Gu Zheng.
    Removing the restore part for VFS flags
    Updating comments with proper flag conditions
    Display GC background option as ON/OFF
    Revised conditions to stop GC in case of remount

v1: Initial changes for adding remount_fs callback
support.

Cc: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Pankaj Kumar <pankaj.km@samsung.com>
---
 Documentation/filesystems/f2fs.txt |    9 +-
 fs/f2fs/super.c                    |  235 +++++++++++++++++++++++-------------
 2 files changed, 160 insertions(+), 84 deletions(-)

diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index bd3c56c..b91e2f2 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -98,8 +98,13 @@ Cleaning Overhead
 MOUNT OPTIONS
 ================================================================================
 
-background_gc_off      Turn off cleaning operations, namely garbage collection,
-		       triggered in background when I/O subsystem is idle.
+background_gc=%s       Turn on/off cleaning operations, namely garbage
+                       collection, triggered in background when I/O subsystem is
+                       idle. If background_gc=on, it will turn on the garbage
+                       collection and if background_gc=off, garbage collection
+                       will be truned off.
+                       Default value for this option is on. So garbage
+                       collection is on by default.
 disable_roll_forward   Disable the roll-forward recovery routine
 discard                Issue discard/TRIM commands when a segment is cleaned.
 no_heap                Disable heap-style segment allocation which finds free
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index ba56549..5a11484 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -34,7 +34,7 @@
 static struct kmem_cache *f2fs_inode_cachep;
 
 enum {
-	Opt_gc_background_off,
+	Opt_gc_background,
 	Opt_disable_roll_forward,
 	Opt_discard,
 	Opt_noheap,
@@ -46,7 +46,7 @@ enum {
 };
 
 static match_table_t f2fs_tokens = {
-	{Opt_gc_background_off, "background_gc_off"},
+	{Opt_gc_background, "background_gc=%s"},
 	{Opt_disable_roll_forward, "disable_roll_forward"},
 	{Opt_discard, "discard"},
 	{Opt_noheap, "no_heap"},
@@ -76,6 +76,91 @@ static void init_once(void *foo)
 	inode_init_once(&fi->vfs_inode);
 }
 
+static int parse_options(struct super_block *sb, char *options)
+{
+	struct f2fs_sb_info *sbi = F2FS_SB(sb);
+	substring_t args[MAX_OPT_ARGS];
+	char *p, *name;
+	int arg = 0;
+
+	if (!options)
+		return 0;
+
+	while ((p = strsep(&options, ",")) != NULL) {
+		int token;
+		if (!*p)
+			continue;
+		/*
+		 * Initialize args struct so we know whether arg was
+		 * found; some options take optional arguments.
+		 */
+		args[0].to = args[0].from = NULL;
+		token = match_token(p, f2fs_tokens, args);
+
+		switch (token) {
+		case Opt_gc_background:
+			name = match_strdup(&args[0]);
+
+			if (!name)
+				return -ENOMEM;
+			if (!strncmp(name, "on", 2))
+				set_opt(sbi, BG_GC);
+			else if (!strncmp(name, "off", 3))
+				clear_opt(sbi, BG_GC);
+			else {
+				kfree(name);
+				return -EINVAL;
+			}
+			kfree(name);
+			break;
+		case Opt_disable_roll_forward:
+			set_opt(sbi, DISABLE_ROLL_FORWARD);
+			break;
+		case Opt_discard:
+			set_opt(sbi, DISCARD);
+			break;
+		case Opt_noheap:
+			set_opt(sbi, NOHEAP);
+			break;
+#ifdef CONFIG_F2FS_FS_XATTR
+		case Opt_nouser_xattr:
+			clear_opt(sbi, XATTR_USER);
+			break;
+#else
+		case Opt_nouser_xattr:
+			f2fs_msg(sb, KERN_INFO,
+				"nouser_xattr options not supported");
+			break;
+#endif
+#ifdef CONFIG_F2FS_FS_POSIX_ACL
+		case Opt_noacl:
+			clear_opt(sbi, POSIX_ACL);
+			break;
+#else
+		case Opt_noacl:
+			f2fs_msg(sb, KERN_INFO, "noacl options not supported");
+			break;
+#endif
+		case Opt_active_logs:
+			if (args->from && match_int(args, &arg))
+				return -EINVAL;
+			if (arg != 2 && arg != 4 && arg != NR_CURSEG_TYPE)
+				return -EINVAL;
+			sbi->active_logs = arg;
+			break;
+		case Opt_disable_ext_identify:
+			set_opt(sbi, DISABLE_EXT_IDENTIFY);
+			break;
+		default:
+			f2fs_msg(sb, KERN_ERR,
+				"Unrecognized mount option \"%s\" or missing value",
+				p);
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
 static struct inode *f2fs_alloc_inode(struct super_block *sb)
 {
 	struct f2fs_inode_info *fi;
@@ -225,10 +310,10 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(root->d_sb);
 
-	if (test_opt(sbi, BG_GC))
-		seq_puts(seq, ",background_gc_on");
+	if (!(root->d_sb->s_flags & MS_RDONLY) && test_opt(sbi, BG_GC))
+		seq_printf(seq, ",background_gc=%s", "on");
 	else
-		seq_puts(seq, ",background_gc_off");
+		seq_printf(seq, ",background_gc=%s", "off");
 	if (test_opt(sbi, DISABLE_ROLL_FORWARD))
 		seq_puts(seq, ",disable_roll_forward");
 	if (test_opt(sbi, DISCARD))
@@ -255,6 +340,58 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 	return 0;
 }
 
+static int f2fs_remount(struct super_block *sb, int *flags, char *data)
+{
+	struct f2fs_sb_info *sbi = F2FS_SB(sb);
+	struct f2fs_mount_info org_mount_opt;
+	int err, active_logs;
+
+	/**
+	 * Save the old mount options in case we
+	 * need to restore them.
+	 */
+	org_mount_opt = sbi->mount_opt;
+	active_logs = sbi->active_logs;
+
+	/* parse mount options */
+	err = parse_options(sb, data);
+	if (err)
+		goto restore_opts;
+
+	/**
+	 * Previous and new state of filesystem is RO,
+	 * so no point in checking GC conditions.
+	 */
+	if ((sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY))
+		goto skip;
+
+	/**
+	 * We stop the GC thread if FS is mounted as RO
+	 * or if background_gc = off is passed in mount
+	 * option. Also sync the filesystem.
+	 */
+	if ((*flags & MS_RDONLY) || !test_opt(sbi, BG_GC)) {
+		if (sbi->gc_thread) {
+			stop_gc_thread(sbi);
+			f2fs_sync_fs(sb, 1);
+		}
+	} else if (test_opt(sbi, BG_GC) && !sbi->gc_thread) {
+		err = start_gc_thread(sbi);
+		if (err)
+			goto restore_opts;
+	}
+skip:
+	/* Update the POSIXACL Flag */
+	 sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
+		(test_opt(sbi, POSIX_ACL) ? MS_POSIXACL : 0);
+	return 0;
+
+restore_opts:
+	sbi->mount_opt = org_mount_opt;
+	sbi->active_logs = active_logs;
+	return err;
+}
+
 static struct super_operations f2fs_sops = {
 	.alloc_inode	= f2fs_alloc_inode,
 	.drop_inode	= f2fs_drop_inode,
@@ -268,6 +405,7 @@ static struct super_operations f2fs_sops = {
 	.freeze_fs	= f2fs_freeze,
 	.unfreeze_fs	= f2fs_unfreeze,
 	.statfs		= f2fs_statfs,
+	.remount_fs	= f2fs_remount,
 };
 
 static struct inode *f2fs_nfs_get_inode(struct super_block *sb,
@@ -315,79 +453,6 @@ static const struct export_operations f2fs_export_ops = {
 	.get_parent = f2fs_get_parent,
 };
 
-static int parse_options(struct super_block *sb, char *options)
-{
-	struct f2fs_sb_info *sbi = F2FS_SB(sb);
-	substring_t args[MAX_OPT_ARGS];
-	char *p;
-	int arg = 0;
-
-	if (!options)
-		return 0;
-
-	while ((p = strsep(&options, ",")) != NULL) {
-		int token;
-		if (!*p)
-			continue;
-		/*
-		 * Initialize args struct so we know whether arg was
-		 * found; some options take optional arguments.
-		 */
-		args[0].to = args[0].from = NULL;
-		token = match_token(p, f2fs_tokens, args);
-
-		switch (token) {
-		case Opt_gc_background_off:
-			clear_opt(sbi, BG_GC);
-			break;
-		case Opt_disable_roll_forward:
-			set_opt(sbi, DISABLE_ROLL_FORWARD);
-			break;
-		case Opt_discard:
-			set_opt(sbi, DISCARD);
-			break;
-		case Opt_noheap:
-			set_opt(sbi, NOHEAP);
-			break;
-#ifdef CONFIG_F2FS_FS_XATTR
-		case Opt_nouser_xattr:
-			clear_opt(sbi, XATTR_USER);
-			break;
-#else
-		case Opt_nouser_xattr:
-			f2fs_msg(sb, KERN_INFO,
-				"nouser_xattr options not supported");
-			break;
-#endif
-#ifdef CONFIG_F2FS_FS_POSIX_ACL
-		case Opt_noacl:
-			clear_opt(sbi, POSIX_ACL);
-			break;
-#else
-		case Opt_noacl:
-			f2fs_msg(sb, KERN_INFO, "noacl options not supported");
-			break;
-#endif
-		case Opt_active_logs:
-			if (args->from && match_int(args, &arg))
-				return -EINVAL;
-			if (arg != 2 && arg != 4 && arg != NR_CURSEG_TYPE)
-				return -EINVAL;
-			sbi->active_logs = arg;
-			break;
-		case Opt_disable_ext_identify:
-			set_opt(sbi, DISABLE_EXT_IDENTIFY);
-			break;
-		default:
-			f2fs_msg(sb, KERN_ERR,
-				"Unrecognized mount option \"%s\" or missing value",
-				p);
-			return -EINVAL;
-		}
-	}
-	return 0;
-}
-
 static loff_t max_file_size(unsigned bits)
 {
 	loff_t result = ADDRS_PER_INODE;
@@ -686,10 +751,16 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 				"Cannot recover all fsync data errno=%ld", err);
 	}
 
-	/* After POR, we can run background GC thread */
-	err = start_gc_thread(sbi);
-	if (err)
-		goto fail;
+	/**
+	 * If filesystem is not mounted as read-only then
+	 * do start the gc_thread.
+	 */
+	if (!(sb->s_flags & MS_RDONLY)) {
+		/* After POR, we can run background GC thread.*/
+		err = start_gc_thread(sbi);
+		if (err)
+			goto fail;
+	}
 
 	err = f2fs_build_stats(sbi);
 	if (err)
-- 
1.7.9.5

Re: [PATCH 1/2] f2fs: add remount_fs callback support

[Gu Zheng]

On 06/16/2013 08:48 AM, Namjae Jeon wrote:

> From: Namjae Jeon <namjae.jeon@samsung.com>
> 
> Add the f2fs_remount function call which will be used
> during the filesystem remounting. This function
> will help us to change the mount options specific to
> f2fs.
> 
> Also modify the f2fs background_gc mount option, which
> will allow the user to dynamically trun on/off the
> garbage collection in f2fs based on the background_gc
> value. If background_gc=on, Garbage collection will
> be turned off & if background_gc=off, Garbage collection
> will be truned on.
> 
> By default the garbage collection is on in f2fs.
> 
> Change Log:
> v2: Incorporated the review comments by Gu Zheng.
>     Removing the restore part for VFS flags
>     Updating comments with proper flag conditions
>     Display GC background option as ON/OFF
>     Revised conditions to stop GC in case of remount
> 
> v1: Initial changes for adding remount_fs callback
> support.
> 
> Cc: Gu Zheng <guz.fnst@cn.fujitsu.com>
> Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
> Signed-off-by: Pankaj Kumar <pankaj.km@samsung.com>


Reviewed-by: Gu Zheng <guz.fnst@cn.fujitsu.com>

Thanks,
Gu

> ---
>  Documentation/filesystems/f2fs.txt |    9 +-
>  fs/f2fs/super.c                    |  235 +++++++++++++++++++++++-------------
>  2 files changed, 160 insertions(+), 84 deletions(-)
> 
> diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
> index bd3c56c..b91e2f2 100644
> --- a/Documentation/filesystems/f2fs.txt
> +++ b/Documentation/filesystems/f2fs.txt
> @@ -98,8 +98,13 @@ Cleaning Overhead
>  MOUNT OPTIONS
>  ================================================================================
>  
> -background_gc_off      Turn off cleaning operations, namely garbage collection,
> -		       triggered in background when I/O subsystem is idle.
> +background_gc=%s       Turn on/off cleaning operations, namely garbage
> +                       collection, triggered in background when I/O subsystem is
> +                       idle. If background_gc=on, it will turn on the garbage
> +                       collection and if background_gc=off, garbage collection
> +                       will be truned off.
> +                       Default value for this option is on. So garbage
> +                       collection is on by default.
>  disable_roll_forward   Disable the roll-forward recovery routine
>  discard                Issue discard/TRIM commands when a segment is cleaned.
>  no_heap                Disable heap-style segment allocation which finds free
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index ba56549..5a11484 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -34,7 +34,7 @@
>  static struct kmem_cache *f2fs_inode_cachep;
>  
>  enum {
> -	Opt_gc_background_off,
> +	Opt_gc_background,
>  	Opt_disable_roll_forward,
>  	Opt_discard,
>  	Opt_noheap,
> @@ -46,7 +46,7 @@ enum {
>  };
>  
>  static match_table_t f2fs_tokens = {
> -	{Opt_gc_background_off, "background_gc_off"},
> +	{Opt_gc_background, "background_gc=%s"},
>  	{Opt_disable_roll_forward, "disable_roll_forward"},
>  	{Opt_discard, "discard"},
>  	{Opt_noheap, "no_heap"},
> @@ -76,6 +76,91 @@ static void init_once(void *foo)
>  	inode_init_once(&fi->vfs_inode);
>  }
>  
> +static int parse_options(struct super_block *sb, char *options)
> +{
> +	struct f2fs_sb_info *sbi = F2FS_SB(sb);
> +	substring_t args[MAX_OPT_ARGS];
> +	char *p, *name;
> +	int arg = 0;
> +
> +	if (!options)
> +		return 0;
> +
> +	while ((p = strsep(&options, ",")) != NULL) {
> +		int token;
> +		if (!*p)
> +			continue;
> +		/*
> +		 * Initialize args struct so we know whether arg was
> +		 * found; some options take optional arguments.
> +		 */
> +		args[0].to = args[0].from = NULL;
> +		token = match_token(p, f2fs_tokens, args);
> +
> +		switch (token) {
> +		case Opt_gc_background:
> +			name = match_strdup(&args[0]);
> +
> +			if (!name)
> +				return -ENOMEM;
> +			if (!strncmp(name, "on", 2))
> +				set_opt(sbi, BG_GC);
> +			else if (!strncmp(name, "off", 3))
> +				clear_opt(sbi, BG_GC);
> +			else {
> +				kfree(name);
> +				return -EINVAL;
> +			}
> +			kfree(name);
> +			break;
> +		case Opt_disable_roll_forward:
> +			set_opt(sbi, DISABLE_ROLL_FORWARD);
> +			break;
> +		case Opt_discard:
> +			set_opt(sbi, DISCARD);
> +			break;
> +		case Opt_noheap:
> +			set_opt(sbi, NOHEAP);
> +			break;
> +#ifdef CONFIG_F2FS_FS_XATTR
> +		case Opt_nouser_xattr:
> +			clear_opt(sbi, XATTR_USER);
> +			break;
> +#else
> +		case Opt_nouser_xattr:
> +			f2fs_msg(sb, KERN_INFO,
> +				"nouser_xattr options not supported");
> +			break;
> +#endif
> +#ifdef CONFIG_F2FS_FS_POSIX_ACL
> +		case Opt_noacl:
> +			clear_opt(sbi, POSIX_ACL);
> +			break;
> +#else
> +		case Opt_noacl:
> +			f2fs_msg(sb, KERN_INFO, "noacl options not supported");
> +			break;
> +#endif
> +		case Opt_active_logs:
> +			if (args->from && match_int(args, &arg))
> +				return -EINVAL;
> +			if (arg != 2 && arg != 4 && arg != NR_CURSEG_TYPE)
> +				return -EINVAL;
> +			sbi->active_logs = arg;
> +			break;
> +		case Opt_disable_ext_identify:
> +			set_opt(sbi, DISABLE_EXT_IDENTIFY);
> +			break;
> +		default:
> +			f2fs_msg(sb, KERN_ERR,
> +				"Unrecognized mount option \"%s\" or missing value",
> +				p);
> +			return -EINVAL;
> +		}
> +	}
> +	return 0;
> +}
> +
>  static struct inode *f2fs_alloc_inode(struct super_block *sb)
>  {
>  	struct f2fs_inode_info *fi;
> @@ -225,10 +310,10 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
>  {
>  	struct f2fs_sb_info *sbi = F2FS_SB(root->d_sb);
>  
> -	if (test_opt(sbi, BG_GC))
> -		seq_puts(seq, ",background_gc_on");
> +	if (!(root->d_sb->s_flags & MS_RDONLY) && test_opt(sbi, BG_GC))
> +		seq_printf(seq, ",background_gc=%s", "on");
>  	else
> -		seq_puts(seq, ",background_gc_off");
> +		seq_printf(seq, ",background_gc=%s", "off");
>  	if (test_opt(sbi, DISABLE_ROLL_FORWARD))
>  		seq_puts(seq, ",disable_roll_forward");
>  	if (test_opt(sbi, DISCARD))
> @@ -255,6 +340,58 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
>  	return 0;
>  }
>  
> +static int f2fs_remount(struct super_block *sb, int *flags, char *data)
> +{
> +	struct f2fs_sb_info *sbi = F2FS_SB(sb);
> +	struct f2fs_mount_info org_mount_opt;
> +	int err, active_logs;
> +
> +	/**
> +	 * Save the old mount options in case we
> +	 * need to restore them.
> +	 */
> +	org_mount_opt = sbi->mount_opt;
> +	active_logs = sbi->active_logs;
> +
> +	/* parse mount options */
> +	err = parse_options(sb, data);
> +	if (err)
> +		goto restore_opts;
> +
> +	/**
> +	 * Previous and new state of filesystem is RO,
> +	 * so no point in checking GC conditions.
> +	 */
> +	if ((sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY))
> +		goto skip;
> +
> +	/**
> +	 * We stop the GC thread if FS is mounted as RO
> +	 * or if background_gc = off is passed in mount
> +	 * option. Also sync the filesystem.
> +	 */
> +	if ((*flags & MS_RDONLY) || !test_opt(sbi, BG_GC)) {
> +		if (sbi->gc_thread) {
> +			stop_gc_thread(sbi);
> +			f2fs_sync_fs(sb, 1);
> +		}
> +	} else if (test_opt(sbi, BG_GC) && !sbi->gc_thread) {
> +		err = start_gc_thread(sbi);
> +		if (err)
> +			goto restore_opts;
> +	}
> +skip:
> +	/* Update the POSIXACL Flag */
> +	 sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
> +		(test_opt(sbi, POSIX_ACL) ? MS_POSIXACL : 0);
> +	return 0;
> +
> +restore_opts:
> +	sbi->mount_opt = org_mount_opt;
> +	sbi->active_logs = active_logs;
> +	return err;
> +}
> +
>  static struct super_operations f2fs_sops = {
>  	.alloc_inode	= f2fs_alloc_inode,
>  	.drop_inode	= f2fs_drop_inode,
> @@ -268,6 +405,7 @@ static struct super_operations f2fs_sops = {
>  	.freeze_fs	= f2fs_freeze,
>  	.unfreeze_fs	= f2fs_unfreeze,
>  	.statfs		= f2fs_statfs,
> +	.remount_fs	= f2fs_remount,
>  };
>  
>  static struct inode *f2fs_nfs_get_inode(struct super_block *sb,
> @@ -315,79 +453,6 @@ static const struct export_operations f2fs_export_ops = {
>  	.get_parent = f2fs_get_parent,
>  };
>  
> -static int parse_options(struct super_block *sb, char *options)
> -{
> -	struct f2fs_sb_info *sbi = F2FS_SB(sb);
> -	substring_t args[MAX_OPT_ARGS];
> -	char *p;
> -	int arg = 0;
> -
> -	if (!options)
> -		return 0;
> -
> -	while ((p = strsep(&options, ",")) != NULL) {
> -		int token;
> -		if (!*p)
> -			continue;
> -		/*
> -		 * Initialize args struct so we know whether arg was
> -		 * found; some options take optional arguments.
> -		 */
> -		args[0].to = args[0].from = NULL;
> -		token = match_token(p, f2fs_tokens, args);
> -
> -		switch (token) {
> -		case Opt_gc_background_off:
> -			clear_opt(sbi, BG_GC);
> -			break;
> -		case Opt_disable_roll_forward:
> -			set_opt(sbi, DISABLE_ROLL_FORWARD);
> -			break;
> -		case Opt_discard:
> -			set_opt(sbi, DISCARD);
> -			break;
> -		case Opt_noheap:
> -			set_opt(sbi, NOHEAP);
> -			break;
> -#ifdef CONFIG_F2FS_FS_XATTR
> -		case Opt_nouser_xattr:
> -			clear_opt(sbi, XATTR_USER);
> -			break;
> -#else
> -		case Opt_nouser_xattr:
> -			f2fs_msg(sb, KERN_INFO,
> -				"nouser_xattr options not supported");
> -			break;
> -#endif
> -#ifdef CONFIG_F2FS_FS_POSIX_ACL
> -		case Opt_noacl:
> -			clear_opt(sbi, POSIX_ACL);
> -			break;
> -#else
> -		case Opt_noacl:
> -			f2fs_msg(sb, KERN_INFO, "noacl options not supported");
> -			break;
> -#endif
> -		case Opt_active_logs:
> -			if (args->from && match_int(args, &arg))
> -				return -EINVAL;
> -			if (arg != 2 && arg != 4 && arg != NR_CURSEG_TYPE)
> -				return -EINVAL;
> -			sbi->active_logs = arg;
> -			break;
> -		case Opt_disable_ext_identify:
> -			set_opt(sbi, DISABLE_EXT_IDENTIFY);
> -			break;
> -		default:
> -			f2fs_msg(sb, KERN_ERR,
> -				"Unrecognized mount option \"%s\" or missing value",
> -				p);
> -			return -EINVAL;
> -		}
> -	}
> -	return 0;
> -}
> -
>  static loff_t max_file_size(unsigned bits)
>  {
>  	loff_t result = ADDRS_PER_INODE;
> @@ -686,10 +751,16 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>  				"Cannot recover all fsync data errno=%ld", err);
>  	}
>  
> -	/* After POR, we can run background GC thread */
> -	err = start_gc_thread(sbi);
> -	if (err)
> -		goto fail;
> +	/**
> +	 * If filesystem is not mounted as read-only then
> +	 * do start the gc_thread.
> +	 */
> +	if (!(sb->s_flags & MS_RDONLY)) {
> +		/* After POR, we can run background GC thread.*/
> +		err = start_gc_thread(sbi);
> +		if (err)
> +			goto fail;
> +	}
>  
>  	err = f2fs_build_stats(sbi);
>  	if (err)