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From: Nikolay Borisov <nborisov@suse.com>
To: Omar Sandoval <osandov@osandov.com>, linux-btrfs@vger.kernel.org
Cc: kernel-team@fb.com, linux-fsdevel@vger.kernel.org,
	Tejun Heo <tj@kernel.org>
Subject: Re: [RFC PATCH v4 2/6] vfs: update swap_{,de}activate documentation
Date: Fri, 25 May 2018 12:15:38 +0300	[thread overview]
Message-ID: <4ebdc19f-d904-3b87-ded0-6a2a405eedbe@suse.com> (raw)
In-Reply-To: <4578bf3c7543f6f9a95b14a0523f2066f58ad43d.1527197312.git.osandov@fb.com>



On 25.05.2018 00:41, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> The documentation for these functions is wrong in several ways:
> 
> - swap_activate() is called with the inode locked
> - swap_activate() takes a swap_info_struct * and a sector_t *
> - swap_activate() can also return a positive number of extents it added
>   itself
> - swap_deactivate() does not return anything
> 
> Signed-off-by: Omar Sandoval <osandov@fb.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  Documentation/filesystems/Locking | 17 +++++++----------
>  Documentation/filesystems/vfs.txt | 12 ++++++++----
>  2 files changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
> index 75d2d57e2c44..7f009e98fa3c 100644
> --- a/Documentation/filesystems/Locking
> +++ b/Documentation/filesystems/Locking
> @@ -211,8 +211,9 @@ prototypes:
>  	int (*launder_page)(struct page *);
>  	int (*is_partially_uptodate)(struct page *, unsigned long, unsigned long);
>  	int (*error_remove_page)(struct address_space *, struct page *);
> -	int (*swap_activate)(struct file *);
> -	int (*swap_deactivate)(struct file *);
> +	int (*swap_activate)(struct swap_info_struct *, struct file *,
> +			     sector_t *);
> +	void (*swap_deactivate)(struct file *);
>  
>  locking rules:
>  	All except set_page_dirty and freepage may block
> @@ -236,8 +237,8 @@ putback_page:		yes
>  launder_page:		yes
>  is_partially_uptodate:	yes
>  error_remove_page:	yes
> -swap_activate:		no
> -swap_deactivate:	no
> +swap_activate:					yes
> +swap_deactivate:				no
>  
>  	->write_begin(), ->write_end() and ->readpage() may be called from
>  the request handler (/dev/loop).
> @@ -334,14 +335,10 @@ cleaned, or an error value if not. Note that in order to prevent the page
>  getting mapped back in and redirtied, it needs to be kept locked
>  across the entire operation.
>  
> -	->swap_activate will be called with a non-zero argument on
> -files backing (non block device backed) swapfiles. A return value
> -of zero indicates success, in which case this file can be used for
> -backing swapspace. The swapspace operations will be proxied to the
> -address space operations.
> +	->swap_activate is called from sys_swapon() with the inode locked.
>  
>  	->swap_deactivate() will be called in the sys_swapoff()
> -path after ->swap_activate() returned success.
> +path after ->swap_activate() returned success. The inode is not locked.
>  
>  ----------------------- file_lock_operations ------------------------------
>  prototypes:
> diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
> index 5fd325df59e2..0149109d94d1 100644
> --- a/Documentation/filesystems/vfs.txt
> +++ b/Documentation/filesystems/vfs.txt
> @@ -650,8 +650,9 @@ struct address_space_operations {
>  					unsigned long);
>  	void (*is_dirty_writeback) (struct page *, bool *, bool *);
>  	int (*error_remove_page) (struct mapping *mapping, struct page *page);
> -	int (*swap_activate)(struct file *);
> -	int (*swap_deactivate)(struct file *);
> +	int (*swap_activate)(struct swap_info_struct *, struct file *,
> +			     sector_t *);
> +	void (*swap_deactivate)(struct file *);
>  };
>  
>    writepage: called by the VM to write a dirty page to backing store.
> @@ -828,8 +829,11 @@ struct address_space_operations {
>  
>    swap_activate: Called when swapon is used on a file to allocate
>  	space if necessary and pin the block lookup information in
> -	memory. A return value of zero indicates success,
> -	in which case this file can be used to back swapspace.
> +	memory. If this returns zero, the swap system will call the address
> +	space operations ->readpage() and ->direct_IO(). Alternatively, this
> +	may call add_swap_extent() and return the number of extents added, in
> +	which case the swap system will use the provided blocks directly
> +	instead of going through the filesystem.
>  
>    swap_deactivate: Called during swapoff on files where swap_activate
>  	was successful.
> 

  reply	other threads:[~2018-05-25  9:15 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-24 21:41 [RFC PATCH v4 0/6] Btrfs: implement swap file support Omar Sandoval
2018-05-24 21:41 ` [RFC PATCH v4 1/6] mm: split SWP_FILE into SWP_ACTIVATED and SWP_FS Omar Sandoval
2018-05-25  9:11   ` Nikolay Borisov
2018-05-24 21:41 ` [RFC PATCH v4 2/6] vfs: update swap_{,de}activate documentation Omar Sandoval
2018-05-25  9:15   ` Nikolay Borisov [this message]
2018-05-24 21:41 ` [RFC PATCH v4 3/6] Btrfs: push EXCL_OP set into btrfs_rm_device() Omar Sandoval
2018-05-25  9:19   ` Nikolay Borisov
2018-05-28 13:29   ` David Sterba
2018-05-24 21:41 ` [RFC PATCH v4 4/6] Btrfs: prevent ioctls from interfering with a swap file Omar Sandoval
2018-05-25 14:50   ` David Sterba
2018-05-25 16:00     ` Omar Sandoval
2018-05-25 16:10       ` David Sterba
2018-08-21  8:46         ` Omar Sandoval
2018-05-24 21:41 ` [RFC PATCH v4 5/6] Btrfs: rename get_chunk_map() and make it non-static Omar Sandoval
2018-05-25  9:21   ` Nikolay Borisov
2018-05-25 16:02     ` Omar Sandoval
2018-05-24 21:41 ` [RFC PATCH v4 6/6] Btrfs: support swap files Omar Sandoval
2018-05-25 10:07   ` Nikolay Borisov
2018-05-25 16:16     ` Omar Sandoval
2018-05-28 13:46   ` David Sterba

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