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Date:   Wed, 14 Sep 2022 11:16:45 -0700
From:   "Darrick J. Wong" <djwong@kernel.org>
To:     Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc:     linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
        nvdimm@lists.linux.dev, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org, dan.j.williams@intel.com,
        david@fromorbit.com, hch@infradead.org, jane.chu@oracle.com
Subject: Re: [PATCH 2/3] fs: move drop_pagecache_sb() for others to use
Message-ID: <YyIajcWz/h1k3kvq@magnolia>
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On Fri, Sep 02, 2022 at 10:36:00AM +0000, Shiyang Ruan wrote:
> xfs_notify_failure requires a method to invalidate all mappings.
> drop_pagecache_sb() can do this but it is a static function and only
> build with CONFIG_SYSCTL.  Now, move it to super.c and make it available
> for others.
> 
> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> ---
>  fs/drop_caches.c   | 33 ---------------------------------
>  fs/super.c         | 34 ++++++++++++++++++++++++++++++++++
>  include/linux/fs.h |  1 +
>  3 files changed, 35 insertions(+), 33 deletions(-)
> 
> diff --git a/fs/drop_caches.c b/fs/drop_caches.c
> index e619c31b6bd9..5c8406076f9b 100644
> --- a/fs/drop_caches.c
> +++ b/fs/drop_caches.c
> @@ -3,7 +3,6 @@
>   * Implement the manual drop-all-pagecache function
>   */
>  
> -#include <linux/pagemap.h>
>  #include <linux/kernel.h>
>  #include <linux/mm.h>
>  #include <linux/fs.h>
> @@ -15,38 +14,6 @@
>  /* A global variable is a bit ugly, but it keeps the code simple */
>  int sysctl_drop_caches;
>  
> -static void drop_pagecache_sb(struct super_block *sb, void *unused)
> -{
> -	struct inode *inode, *toput_inode = NULL;
> -
> -	spin_lock(&sb->s_inode_list_lock);
> -	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
> -		spin_lock(&inode->i_lock);
> -		/*
> -		 * We must skip inodes in unusual state. We may also skip
> -		 * inodes without pages but we deliberately won't in case
> -		 * we need to reschedule to avoid softlockups.
> -		 */
> -		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
> -		    (mapping_empty(inode->i_mapping) && !need_resched())) {
> -			spin_unlock(&inode->i_lock);
> -			continue;
> -		}
> -		__iget(inode);
> -		spin_unlock(&inode->i_lock);
> -		spin_unlock(&sb->s_inode_list_lock);
> -
> -		invalidate_mapping_pages(inode->i_mapping, 0, -1);
> -		iput(toput_inode);
> -		toput_inode = inode;
> -
> -		cond_resched();
> -		spin_lock(&sb->s_inode_list_lock);
> -	}
> -	spin_unlock(&sb->s_inode_list_lock);
> -	iput(toput_inode);
> -}
> -
>  int drop_caches_sysctl_handler(struct ctl_table *table, int write,
>  		void *buffer, size_t *length, loff_t *ppos)
>  {
> diff --git a/fs/super.c b/fs/super.c
> index 734ed584a946..bdf53dbe834c 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -36,6 +36,7 @@
>  #include <linux/lockdep.h>
>  #include <linux/user_namespace.h>
>  #include <linux/fs_context.h>
> +#include <linux/pagemap.h>
>  #include <uapi/linux/mount.h>
>  #include "internal.h"
>  
> @@ -677,6 +678,39 @@ void drop_super_exclusive(struct super_block *sb)
>  }
>  EXPORT_SYMBOL(drop_super_exclusive);
>  
> +void drop_pagecache_sb(struct super_block *sb, void *unused)
> +{
> +	struct inode *inode, *toput_inode = NULL;
> +
> +	spin_lock(&sb->s_inode_list_lock);
> +	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
> +		spin_lock(&inode->i_lock);
> +		/*
> +		 * We must skip inodes in unusual state. We may also skip
> +		 * inodes without pages but we deliberately won't in case
> +		 * we need to reschedule to avoid softlockups.
> +		 */
> +		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
> +		    (mapping_empty(inode->i_mapping) && !need_resched())) {
> +			spin_unlock(&inode->i_lock);
> +			continue;
> +		}
> +		__iget(inode);
> +		spin_unlock(&inode->i_lock);
> +		spin_unlock(&sb->s_inode_list_lock);
> +
> +		invalidate_mapping_pages(inode->i_mapping, 0, -1);
> +		iput(toput_inode);
> +		toput_inode = inode;
> +
> +		cond_resched();
> +		spin_lock(&sb->s_inode_list_lock);
> +	}
> +	spin_unlock(&sb->s_inode_list_lock);
> +	iput(toput_inode);
> +}
> +EXPORT_SYMBOL(drop_pagecache_sb);

You might want to rename this "super_drop_pagecache" to fit with the
other functions that all have "super" in the name somewhere.

--D

> +
>  static void __iterate_supers(void (*f)(struct super_block *))
>  {
>  	struct super_block *sb, *p = NULL;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9eced4cc286e..5ded28c0d2c9 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3292,6 +3292,7 @@ extern struct super_block *get_super(struct block_device *);
>  extern struct super_block *get_active_super(struct block_device *bdev);
>  extern void drop_super(struct super_block *sb);
>  extern void drop_super_exclusive(struct super_block *sb);
> +void drop_pagecache_sb(struct super_block *sb, void *unused);
>  extern void iterate_supers(void (*)(struct super_block *, void *), void *);
>  extern void iterate_supers_type(struct file_system_type *,
>  			        void (*)(struct super_block *, void *), void *);
> -- 
> 2.37.2
>