From: NeilBrown <neilb@suse.de>
To: Trond Myklebust <trond.myklebust@hammerspace.com>,
Anna Schumaker <anna.schumaker@netapp.com>,
Chuck Lever <chuck.lever@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
Christoph Hellwig <hch@infradead.org>,
David Howells <dhowells@redhat.com>
Cc: linux-nfs@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 08/23] DOC: update documentation for swap_activate and swap_rw
Date: Mon, 24 Jan 2022 14:48:32 +1100 [thread overview]
Message-ID: <164299611278.26253.2945860698197438729.stgit@noble.brown> (raw)
In-Reply-To: <164299573337.26253.7538614611220034049.stgit@noble.brown>
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swap_activate() has been out-of-date for a long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()
Signed-off-by: NeilBrown <neilb@suse.de>
---
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 3f9b1497ebb8..fbb10378d5ee 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -260,8 +260,9 @@ 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_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 set_page_dirty 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 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() 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 bf5c48066fac..779d23fc7954 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -751,8 +751,9 @@ cache in your filesystem. The following members are defined:
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_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``
@@ -959,15 +960,21 @@ 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
===============
next prev parent reply other threads:[~2022-01-24 3:51 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-24 3:48 [PATCH 00/23 V3] Repair SWAP-over_NFS NeilBrown
2022-01-24 3:48 ` [PATCH 05/23] MM: reclaim mustn't enter FS for SWP_FS_OPS swap-space NeilBrown
2022-01-24 7:31 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 03/23] MM: drop swap_set_page_dirty NeilBrown
2022-01-24 7:28 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 14/23] NFS: swap IO handling is slightly different for O_DIRECT IO NeilBrown
2022-01-24 8:58 ` Christoph Hellwig
2022-01-24 13:22 ` Mark Hemment
2022-01-26 22:51 ` NeilBrown
2022-01-24 3:48 ` [PATCH 22/23] NFS: swap-out must always use STABLE writes NeilBrown
2022-01-26 3:45 ` Trond Myklebust
2022-01-26 21:42 ` NeilBrown
2022-01-24 3:48 ` [PATCH 23/23] SUNRPC: lock against ->sock changing during sysfs read NeilBrown
2022-01-24 3:48 ` NeilBrown [this message]
2022-01-24 8:50 ` [PATCH 08/23] DOC: update documentation for swap_activate and swap_rw Christoph Hellwig
2022-01-24 3:48 ` [PATCH 07/23] MM: perform async writes to SWP_FS_OPS swap-space using ->swap_rw NeilBrown
2022-01-24 8:49 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 02/23] MM: extend block-plugging to cover all swap reads with read-ahead NeilBrown
2022-01-24 7:27 ` Christoph Hellwig
2022-01-26 21:47 ` NeilBrown
2022-01-26 23:09 ` Hugh Dickins
2022-01-27 0:32 ` NeilBrown
2022-01-24 3:48 ` [PATCH 16/23] SUNRPC/auth: async tasks mustn't block waiting for memory NeilBrown
2022-01-24 3:48 ` [PATCH 04/23] MM: move responsibility for setting SWP_FS_OPS to ->swap_activate NeilBrown
2022-01-24 7:30 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 06/23] MM: introduce ->swap_rw and use it for reads from SWP_FS_OPS swap-space NeilBrown
2022-01-24 8:48 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 15/23] SUNRPC/call_alloc: async tasks mustn't block waiting for memory NeilBrown
2022-01-24 3:48 ` [PATCH 20/23] SUNRPC: improve 'swap' handling: scheduling and PF_MEMALLOC NeilBrown
2022-01-24 3:48 ` [PATCH 01/23] MM: create new mm/swap.h header file NeilBrown
2022-02-07 13:51 ` Geert Uytterhoeven
2022-01-24 3:48 ` [PATCH 09/23] MM: submit multipage reads for SWP_FS_OPS swap-space NeilBrown
2022-01-24 8:25 ` kernel test robot
2022-01-24 8:52 ` Christoph Hellwig
2022-01-24 9:27 ` kernel test robot
2022-01-24 13:16 ` Mark Hemment
2022-01-26 22:04 ` NeilBrown
2022-02-08 11:07 ` Geert Uytterhoeven
2022-01-24 3:48 ` [PATCH 12/23] NFS: remove IS_SWAPFILE hack NeilBrown
2022-01-24 8:56 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 19/23] NFS: discard NFS_RPC_SWAPFLAGS and RPC_TASK_ROOTCREDS NeilBrown
2022-01-24 3:48 ` [PATCH 17/23] SUNRPC/xprt: async tasks mustn't block waiting for memory NeilBrown
2022-01-24 3:48 ` [PATCH 18/23] SUNRPC: remove scheduling boost for "SWAPPER" tasks NeilBrown
2022-01-24 3:48 ` [PATCH 21/23] NFSv4: keep state manager thread active if swap is enabled NeilBrown
2022-01-24 3:48 ` [PATCH 11/23] VFS: Add FMODE_CAN_ODIRECT file flag NeilBrown
2022-01-24 8:56 ` Christoph Hellwig
2022-01-26 22:14 ` NeilBrown
2022-01-24 3:48 ` [PATCH 10/23] MM: submit multipage write for SWP_FS_OPS swap-space NeilBrown
2022-01-24 8:55 ` Christoph Hellwig
2022-01-24 10:29 ` kernel test robot
2022-01-24 3:48 ` [PATCH 13/23] NFS: rename nfs_direct_IO and use as ->swap_rw NeilBrown
2022-01-24 8:57 ` Christoph Hellwig
2022-02-07 17:55 ` [PATCH 00/23 V3] Repair SWAP-over_NFS Geert Uytterhoeven
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