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SubjectRe: [PATCH 1/2] f2fs: add remount_fs callback support
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,
I think splitting these two changes into single ones seems better.
Refer to the inline comments.

Thanks,
Gu

>
> By default the garbage collection is on in f2fs.
>
> Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
> Signed-off-by: Pankaj Kumar <pankaj.km@samsung.com>

> ---
> Documentation/filesystems/f2fs.txt | 8 +-
> fs/f2fs/super.c | 223 +++++++++++++++++++++++-------------
> 2 files changed, 148 insertions(+), 83 deletions(-)
>
> diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
> index bd3c56c..6a036ce 100644
> --- a/Documentation/filesystems/f2fs.txt
> +++ b/Documentation/filesystems/f2fs.txt
> @@ -98,8 +98,12 @@ 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=%u Turn on/off cleaning operations, namely garbage collection,
> + triggered in background when I/O subsystem is idle. If
> + background_gc=1, it will turn on the garbage collection &
> + if background_gc=0, garbage collection will be truned off.
> + Default value for this option is 1. 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 3ac305d..bcd68aa 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=%u"},
> {Opt_disable_roll_forward, "disable_roll_forward"},
> {Opt_discard, "discard"},
> {Opt_noheap, "no_heap"},
> @@ -76,6 +76,86 @@ static void init_once(void *foo)
> inode_init_once(&fi->vfs_inode);
> }
>
> +static int parse_options(struct super_block *sb, struct f2fs_sb_info *sbi,
> + char *options)
> +{
> + 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:
> + if (args->from && match_int(args, &arg))
> + return -EINVAL;
> + if (arg != 0 && arg != 1)
> + return -EINVAL;
> + if (arg == 0)
> + clear_opt(sbi, BG_GC);
> + else
> + set_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 struct inode *f2fs_alloc_inode(struct super_block *sb)
> {
> struct f2fs_inode_info *fi;
> @@ -214,10 +294,10 @@ 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=%u", 1);
> else
> - seq_puts(seq, ",background_gc_off");
> + seq_printf(seq, ",background_gc=%u", 0);


Though simply option show is enough, but I think the "background_gc=on/off" is more friendly.

> if (test_opt(sbi, DISABLE_ROLL_FORWARD))
> seq_puts(seq, ",disable_roll_forward");
> if (test_opt(sbi, DISCARD))
> @@ -244,6 +324,52 @@ 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);
> + unsigned long old_sb_flags;
> + struct f2fs_mount_info org_mount_opt;
> + int err, active_logs;
> +
> + /**
> + * Save the old mount options in case we
> + * need to restore them.
> + */
> + old_sb_flags = sb->s_flags;
> + org_mount_opt = sbi->mount_opt;
> + active_logs = sbi->active_logs;
> +
> + /* parse mount options */
> + err = parse_options(sb, sbi, data);
> + if (err)
> + goto restore_opts;
> +
> + /**
> + * 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.

> + 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.

> + 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.

> + 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,
> @@ -256,6 +382,7 @@ 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,
> @@ -303,78 +430,6 @@ static const struct export_operations f2fs_export_ops = {
> .get_parent = f2fs_get_parent,
> };
>
> -static int parse_options(struct super_block *sb, struct f2fs_sb_info *sbi,
> - char *options)
> -{
> - 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)
> {
> @@ -674,10 +729,16 @@ 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;
> + /* 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.

> + err = start_gc_thread(sbi);
> + if (err)
> + goto fail;
> + }
>
> err = f2fs_build_stats(sbi);
> if (err)




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