On Fri, 02 Feb 2007 13:50:10 -1000
[EMAIL PROTECTED] wrote:
>
>
> This adds the ability for the file system to remounted as read only during a
> system suspend. Log the mount points so when the resume occurs, they can be
> remounted back to their original states. This is so in an advent of a power
> failure, we try our best to keep data from being corrupted or lost.
>
Well the code appears simple enough, but I've not previously heard anyone
express a need for this feature. But I know how to cc people who might
have heard this.
Minor coding-style observations:
>
> diff -puN fs/super.c~suspend_fs_ro fs/super.c
> --- linux-2.6_sdio/fs/super.c~suspend_fs_ro 2007-02-01 13:35:46.000000000
> -1000
> +++ linux-2.6_sdio-akuster/fs/super.c 2007-02-01 13:35:50.000000000 -1000
> @@ -47,6 +47,70 @@ struct file_system_type *get_fs_type(con
> LIST_HEAD(super_blocks);
> DEFINE_SPINLOCK(sb_lock);
>
> +#ifdef CONFIG_SUSPEND_REMOUNTFS
> +/*
> + * Code to preserve filesystem data during suspend.
> + */
> +
> +struct suspremount {
> +struct super_block *sb;
> +struct suspremount *next;
> +};
The fields of this struct need a leading tab.
The name "suspremount" might be unpopular. suspend_remount_state would be
more kernely.
> +static struct suspremount *suspremount_list;
> +
> +void suspend_remount_log_fs(struct super_block *sb)
> +{
> + struct suspremount *remountp;
> +
> + if ((remountp = (struct suspremount *)
> + kmalloc(sizeof(struct suspremount), GFP_KERNEL)) != NULL) {
The typecast is unneeded, and the compounded assign-and-test is not
preferred style. So here, please use
struct suspremount *remountp;
remountp = kmalloc(sizeof(*remountp), GFP_KERNEL);
if (remountp != NULL) {
> +
> +/*
> + * Remount filesystems prior to suspend, in case the
> + * power source is removed (ie, battery removed) or
> + * battery dies during suspend.
> + */
> +
> +void suspend_remount_all_fs_ro(void)
> +{
> + suspremount_list = NULL;
> + emergency_remount();
> +}
> +EXPORT_SYMBOL(suspend_remount_all_fs_ro);
Why is this exported to modules?
> +void resume_remount_fs_rw(void)
> +{
> + struct suspremount *remountp;
> +
> + remountp = suspremount_list;
> +
> + while (remountp != NULL) {
> + struct suspremount *tp;
> + struct super_block *sb;
> + int flags, ret;
> +
> + sb = remountp->sb;
> + flags = 0;
> + if (sb->s_op && sb->s_op->remount_fs) {
> + ret = sb->s_op->remount_fs(sb, &flags, NULL);
> + if (ret) printk("resume_remount_rw: error %d\n", ret);
newline needed here.
super_block_operations.remount_fs() is supposed to be called under lock_super().
Some filesystems might go BUG over this, or something. Was there a reason to
not do this?
> + }
> +
> + tp = remountp->next;
> + kfree(remountp);
> + remountp = tp;
> + }
> + suspremount_list = NULL;
> +}
> +EXPORT_SYMBOL(resume_remount_fs_rw);
Why the export?
All this code is singly-threaded at a much higher level (I hope), hence
that list doesn't need locking. However a comment explaining this might be
good.
> @@ -613,6 +677,9 @@ int do_remount_sb(struct super_block *sb
> unlock_super(sb);
> if (retval)
> return retval;
> +#ifdef CONFIG_SUSPEND_REMOUNTFS
> + suspend_remount_log_fs(sb);
> +#endif
We try to avoid putting ifdefs in C files. So in a header file, do
struct super_block;
#ifdef CONFIG_SUSPEND_REMOUNTFS
extern void suspend_remount_log_fs(struct super_block *sb);
#else
static inline void suspend_remount_log_fs(struct super_block *sb) {}
#endif
> +#ifdef CONFIG_SUSPEND_REMOUNTFS
> + /*
> + * Remount filesystems prior to suspend, in case the
> + * power source is removed (ie, battery removed) or
> + * battery dies during suspend.
> + */
> +
> + suspend_remount_all_fs_ro();
> +#endif
Ditto here.
> +#ifdef CONFIG_SUSPEND_REMOUNTFS
> + resume_remount_fs_rw();
> +#endif
And here.
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