The quilt patch titled
Subject: mm: submit multipage write for SWP_FS_OPS swap-space
has been removed from the -mm tree. Its filename was
mm-submit-multipage-write-for-swp_fs_ops-swap-space.patch
This patch was dropped because it was merged into mm-stable
------------------------------------------------------
From: NeilBrown <neilb@xxxxxxx>
Subject: mm: submit multipage write for SWP_FS_OPS swap-space
swap_writepage() is given one page at a time, but may be called repeatedly
in succession.
For block-device swapspace, the blk_plug functionality allows the multiple
pages to be combined together at lower layers. That cannot be used for
SWP_FS_OPS as blk_plug may not exist - it is only active when
CONFIG_BLOCK=y. Consequently all swap reads over NFS are single page
reads.
With this patch we pass a pointer-to-pointer via the wbc. swap_writepage
can store state between calls - much like the pointer passed explicitly to
swap_readpage. After calling swap_writepage() some number of times, the
state will be passed to swap_write_unplug() which can submit the combined
request.
Link: https://lkml.kernel.org/r/164859778128.29473.5191868522654408537.stgit@noble.brown
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Tested-by: David Howells <dhowells@xxxxxxxxxx>
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/writeback.h | 7 +++
mm/page_io.c | 78 +++++++++++++++++++++++++-----------
mm/swap.h | 4 +
mm/vmscan.c | 9 +++-
4 files changed, 74 insertions(+), 24 deletions(-)
--- a/include/linux/writeback.h~mm-submit-multipage-write-for-swp_fs_ops-swap-space
+++ a/include/linux/writeback.h
@@ -80,6 +80,13 @@ struct writeback_control {
unsigned punt_to_cgroup:1; /* cgrp punting, see __REQ_CGROUP_PUNT */
+ /* To enable batching of swap writes to non-block-device backends,
+ * "plug" can be set point to a 'struct swap_iocb *'. When all swap
+ * writes have been submitted, if with swap_iocb is not NULL,
+ * swap_write_unplug() should be called.
+ */
+ struct swap_iocb **swap_plug;
+
#ifdef CONFIG_CGROUP_WRITEBACK
struct bdi_writeback *wb; /* wb this writeback is issued under */
struct inode *inode; /* inode being written out */
--- a/mm/page_io.c~mm-submit-multipage-write-for-swp_fs_ops-swap-space
+++ a/mm/page_io.c
@@ -259,8 +259,9 @@ static void sio_write_complete(struct ki
{
struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
struct page *page = sio->bvec[0].bv_page;
+ int p;
- if (ret != PAGE_SIZE) {
+ if (ret != PAGE_SIZE * sio->pages) {
/*
* In the case of swap-over-nfs, this can be a
* temporary failure if the system has limited
@@ -271,43 +272,63 @@ static void sio_write_complete(struct ki
* the normal direct-to-bio case as it could
* be temporary.
*/
- set_page_dirty(page);
- ClearPageReclaim(page);
pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
ret, page_file_offset(page));
+ for (p = 0; p < sio->pages; p++) {
+ page = sio->bvec[p].bv_page;
+ set_page_dirty(page);
+ ClearPageReclaim(page);
+ }
} else
- count_vm_event(PSWPOUT);
- end_page_writeback(page);
+ count_vm_events(PSWPOUT, sio->pages);
+
+ for (p = 0; p < sio->pages; p++)
+ end_page_writeback(sio->bvec[p].bv_page);
+
mempool_free(sio, sio_pool);
}
static int swap_writepage_fs(struct page *page, struct writeback_control *wbc)
{
- struct swap_iocb *sio;
+ struct swap_iocb *sio = NULL;
struct swap_info_struct *sis = page_swap_info(page);
struct file *swap_file = sis->swap_file;
- struct address_space *mapping = swap_file->f_mapping;
- struct iov_iter from;
- int ret;
+ loff_t pos = page_file_offset(page);
set_page_writeback(page);
unlock_page(page);
- sio = mempool_alloc(sio_pool, GFP_NOIO);
- init_sync_kiocb(&sio->iocb, swap_file);
- sio->iocb.ki_complete = sio_write_complete;
- sio->iocb.ki_pos = page_file_offset(page);
- sio->bvec[0].bv_page = page;
- sio->bvec[0].bv_len = PAGE_SIZE;
- sio->bvec[0].bv_offset = 0;
- iov_iter_bvec(&from, WRITE, &sio->bvec[0], 1, PAGE_SIZE);
- ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
- if (ret != -EIOCBQUEUED)
- sio_write_complete(&sio->iocb, ret);
- return ret;
+ if (wbc->swap_plug)
+ sio = *wbc->swap_plug;
+ if (sio) {
+ if (sio->iocb.ki_filp != swap_file ||
+ sio->iocb.ki_pos + sio->pages * PAGE_SIZE != pos) {
+ swap_write_unplug(sio);
+ sio = NULL;
+ }
+ }
+ if (!sio) {
+ sio = mempool_alloc(sio_pool, GFP_NOIO);
+ init_sync_kiocb(&sio->iocb, swap_file);
+ sio->iocb.ki_complete = sio_write_complete;
+ sio->iocb.ki_pos = pos;
+ sio->pages = 0;
+ }
+ sio->bvec[sio->pages].bv_page = page;
+ sio->bvec[sio->pages].bv_len = PAGE_SIZE;
+ sio->bvec[sio->pages].bv_offset = 0;
+ sio->pages += 1;
+ if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
+ swap_write_unplug(sio);
+ sio = NULL;
+ }
+ if (wbc->swap_plug)
+ *wbc->swap_plug = sio;
+
+ return 0;
}
int __swap_writepage(struct page *page, struct writeback_control *wbc,
- bio_end_io_t end_write_func)
+ bio_end_io_t end_write_func)
{
struct bio *bio;
int ret;
@@ -344,6 +365,19 @@ int __swap_writepage(struct page *page,
return 0;
}
+void swap_write_unplug(struct swap_iocb *sio)
+{
+ struct iov_iter from;
+ struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
+ int ret;
+
+ iov_iter_bvec(&from, WRITE, sio->bvec, sio->pages,
+ PAGE_SIZE * sio->pages);
+ ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
+ if (ret != -EIOCBQUEUED)
+ sio_write_complete(&sio->iocb, ret);
+}
+
static void sio_read_complete(struct kiocb *iocb, long ret)
{
struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
--- a/mm/swap.h~mm-submit-multipage-write-for-swp_fs_ops-swap-space
+++ a/mm/swap.h
@@ -16,6 +16,7 @@ static inline void swap_read_unplug(stru
if (unlikely(plug))
__swap_read_unplug(plug);
}
+void swap_write_unplug(struct swap_iocb *sio);
int swap_writepage(struct page *page, struct writeback_control *wbc);
void end_swap_bio_write(struct bio *bio);
int __swap_writepage(struct page *page, struct writeback_control *wbc,
@@ -71,6 +72,9 @@ static inline int swap_readpage(struct p
{
return 0;
}
+static inline void swap_write_unplug(struct swap_iocb *sio)
+{
+}
static inline struct address_space *swap_address_space(swp_entry_t entry)
{
--- a/mm/vmscan.c~mm-submit-multipage-write-for-swp_fs_ops-swap-space
+++ a/mm/vmscan.c
@@ -1156,7 +1156,8 @@ typedef enum {
* pageout is called by shrink_page_list() for each dirty page.
* Calls ->writepage().
*/
-static pageout_t pageout(struct folio *folio, struct address_space *mapping)
+static pageout_t pageout(struct folio *folio, struct address_space *mapping,
+ struct swap_iocb **plug)
{
/*
* If the folio is dirty, only perform writeback if that write
@@ -1201,6 +1202,7 @@ static pageout_t pageout(struct folio *f
.range_start = 0,
.range_end = LLONG_MAX,
.for_reclaim = 1,
+ .swap_plug = plug,
};
folio_set_reclaim(folio);
@@ -1533,6 +1535,7 @@ static unsigned int shrink_page_list(str
unsigned int nr_reclaimed = 0;
unsigned int pgactivate = 0;
bool do_demote_pass;
+ struct swap_iocb *plug = NULL;
memset(stat, 0, sizeof(*stat));
cond_resched();
@@ -1814,7 +1817,7 @@ retry:
* starts and then write it out here.
*/
try_to_unmap_flush_dirty();
- switch (pageout(folio, mapping)) {
+ switch (pageout(folio, mapping, &plug)) {
case PAGE_KEEP:
goto keep_locked;
case PAGE_ACTIVATE:
@@ -1968,6 +1971,8 @@ keep:
list_splice(&ret_pages, page_list);
count_vm_events(PGACTIVATE, pgactivate);
+ if (plug)
+ swap_write_unplug(plug);
return nr_reclaimed;
}
_
Patches currently in -mm which might be from neilb@xxxxxxx are
mm-discard-__gfp_atomic.patch
