From patchwork Tue Mar 29 23:49:41 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 12795347 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D36B8C433F5 for ; Tue, 29 Mar 2022 23:52:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 494858D0005; Tue, 29 Mar 2022 19:52:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 41C788D0001; Tue, 29 Mar 2022 19:52:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 297098D0005; Tue, 29 Mar 2022 19:52:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0229.hostedemail.com [216.40.44.229]) by kanga.kvack.org (Postfix) with ESMTP id 161EB8D0001 for ; Tue, 29 Mar 2022 19:52:21 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id C3AA8A4A4A for ; Tue, 29 Mar 2022 23:52:20 +0000 (UTC) X-FDA: 79299075240.22.D3CBBBC Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf07.hostedemail.com (Postfix) with ESMTP id 3F4E140004 for ; Tue, 29 Mar 2022 23:52:20 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 2F6AF218F9; Tue, 29 Mar 2022 23:52:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1648597939; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tE32eedhCbqKNV/qzY0QU0j1sD/lbIXfPgDh2Z7fRTs=; b=npmS5Rtdt/vjDg9rTITOYuf0u/0wOAROyuYict0Yx8Rlg5aAG7crOrIyOIn5n7L9jpR+l3 xRm3PhCNFMQsJ0ujiDy2L6oYKm1FM94lty/8pH2WSGM5CMs0tIlhDERpH4jI7U4LC8JfcK joM92dZM0iUmJ2/asLXy8NyVeEpzxLY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1648597939; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tE32eedhCbqKNV/qzY0QU0j1sD/lbIXfPgDh2Z7fRTs=; b=3wC0HgxOOEeD/3T3+oCgunZQv+J+1MqE6Bd8mMwtFdIWZsqNC9klDTo+16h0XLvnTbFdk4 MQLIjNp7nPKQUXAQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 4922A13A7E; Tue, 29 Mar 2022 23:52:17 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id nFx+ArGbQ2JILwAAMHmgww (envelope-from ); Tue, 29 Mar 2022 23:52:17 +0000 Subject: [PATCH 07/10] DOC: update documentation for swap_activate and swap_rw From: NeilBrown To: Andrew Morton Cc: Christoph Hellwig , David Howells , linux-nfs@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Wed, 30 Mar 2022 10:49:41 +1100 Message-ID: <164859778126.29473.6778751233552859461.stgit@noble.brown> In-Reply-To: <164859751830.29473.5309689752169286816.stgit@noble.brown> References: <164859751830.29473.5309689752169286816.stgit@noble.brown> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Stat-Signature: iufj9eumxog4npyh3k9jkcd8nji5hiim X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3F4E140004 Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=npmS5Rtd; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=3wC0HgxO; dmarc=pass (policy=none) header.from=suse.de; spf=pass (imf07.hostedemail.com: domain of neilb@suse.de designates 195.135.220.28 as permitted sender) smtp.mailfrom=neilb@suse.de X-Rspam-User: X-HE-Tag: 1648597940-230352 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: This documentation for ->swap_activate() has been out-of-date for a long time. This patch updates it to match recent changes, and adds documentation for the associated ->swap_rw() Reviewed-by: Christoph Hellwig Signed-off-by: NeilBrown --- Documentation/filesystems/locking.rst | 18 ++++++++++++------ Documentation/filesystems/vfs.rst | 17 ++++++++++++----- 2 files changed, 24 insertions(+), 11 deletions(-) diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index 2998cec9af4b..009d855c9be5 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -260,8 +260,9 @@ prototypes:: int (*launder_folio)(struct folio *); bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count); int (*error_remove_page)(struct address_space *, struct page *); - int (*swap_activate)(struct file *); + int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span) int (*swap_deactivate)(struct file *); + int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter); locking rules: All except dirty_folio and freepage may block @@ -290,6 +291,7 @@ is_partially_uptodate: yes error_remove_page: yes swap_activate: no swap_deactivate: no +swap_rw: yes, unlocks ====================== ======================== ========= =============== ->write_begin(), ->write_end() and ->readpage() may be called from @@ -392,15 +394,19 @@ cleaned, or an error value if not. Note that in order to prevent the folio 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() will be called to prepare the given file for swap. It +should perform any validation and preparation necessary to ensure that +writes can be performed with minimal memory allocation. It should call +add_swap_extent(), or the helper iomap_swapfile_activate(), and return +the number of extents added. If IO should be submitted through +->swap_rw(), it should set SWP_FS_OPS, otherwise IO will be submitted +directly to the block device ``sis->bdev``. ->swap_deactivate() will be called in the sys_swapoff() path after ->swap_activate() returned success. +->swap_rw will be called for swap IO if SWP_FS_OPS was set by ->swap_activate(). + file_lock_operations ==================== diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index 4f14edf93941..9d3480e089f6 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -751,8 +751,9 @@ cache in your filesystem. The following members are defined: size_t count); 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_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span) int (*swap_deactivate)(struct file *); + int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter); }; ``writepage`` @@ -963,15 +964,21 @@ cache in your filesystem. The following members are defined: unless you have them locked or reference counts increased. ``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. + + Called to prepare the given file for swap. It should perform + any validation and preparation necessary to ensure that writes + can be performed with minimal memory allocation. It should call + add_swap_extent(), or the helper iomap_swapfile_activate(), and + return the number of extents added. If IO should be submitted + through ->swap_rw(), it should set SWP_FS_OPS, otherwise IO will + be submitted directly to the block device ``sis->bdev``. ``swap_deactivate`` Called during swapoff on files where swap_activate was successful. +``swap_rw`` + Called to read or write swap pages when SWP_FS_OPS is set. The File Object ===============