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mm: perform async writes to SWP_FS_OPS swap-space using ->swap_rw 

This patch switches swap-out to SWP_FS_OPS swap-spaces to use ->swap_rw
and makes the writes asynchronous, like they are for other swap spaces.

To make it async we need to allocate the kiocb struct from a mempool. 
This may block, but won't block as long as waiting for the write to
complete.  At most it will wait for some previous swap IO to complete.

Link: https://lkml.kernel.org/r/164859778126.29473.12399585304843922231.stgit@noble.brown
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: David Howells <dhowells@redhat.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
NeilBrown 2022-05-09 18:20:48 -07:00 committed by akpm
parent eb79f3af93
commit 7eadabc05d
1 changed files with 58 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

98
mm/page_io.c
View File

@ -254,6 +254,57 @@ int sio_pool_init(void)
return 0;
}
static void sio_write_complete(struct kiocb *iocb, long ret)
{
struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
struct page *page = sio->bvec.bv_page;
if (ret != PAGE_SIZE) {
/*
* In the case of swap-over-nfs, this can be a
* temporary failure if the system has limited
* memory for allocating transmit buffers.
* Mark the page dirty and avoid
* folio_rotate_reclaimable but rate-limit the
* messages but do not flag PageError like
* 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));
} else
count_vm_event(PSWPOUT);
end_page_writeback(page);
mempool_free(sio, sio_pool);
}
static int swap_writepage_fs(struct page *page, struct writeback_control *wbc)
{
struct swap_iocb *sio;
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;
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.bv_page = page;
sio->bvec.bv_len = PAGE_SIZE;
sio->bvec.bv_offset = 0;
iov_iter_bvec(&from, WRITE, &sio->bvec, 1, PAGE_SIZE);
ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
if (ret != -EIOCBQUEUED)
sio_write_complete(&sio->iocb, ret);
return ret;
}
int __swap_writepage(struct page *page, struct writeback_control *wbc,
bio_end_io_t end_write_func)
{
@ -262,46 +313,13 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
struct swap_info_struct *sis = page_swap_info(page);
VM_BUG_ON_PAGE(!PageSwapCache(page), page);
if (data_race(sis->flags & SWP_FS_OPS)) {
struct kiocb kiocb;
struct file *swap_file = sis->swap_file;
struct address_space *mapping = swap_file->f_mapping;
struct bio_vec bv = {
.bv_page = page,
.bv_len = PAGE_SIZE,
.bv_offset = 0
};
struct iov_iter from;
iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
init_sync_kiocb(&kiocb, swap_file);
kiocb.ki_pos = page_file_offset(page);
set_page_writeback(page);
unlock_page(page);
ret = mapping->a_ops->direct_IO(&kiocb, &from);
if (ret == PAGE_SIZE) {
count_vm_event(PSWPOUT);
ret = 0;
} else {
/*
* In the case of swap-over-nfs, this can be a
* temporary failure if the system has limited
* memory for allocating transmit buffers.
* Mark the page dirty and avoid
* folio_rotate_reclaimable but rate-limit the
* messages but do not flag PageError like
* the normal direct-to-bio case as it could
* be temporary.
*/
set_page_dirty(page);
ClearPageReclaim(page);
pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
page_file_offset(page));
}
end_page_writeback(page);
return ret;
}
/*
* ->flags can be updated non-atomicially (scan_swap_map_slots),
* but that will never affect SWP_FS_OPS, so the data_race
* is safe.
*/
if (data_race(sis->flags & SWP_FS_OPS))
return swap_writepage_fs(page, wbc);
ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
if (!ret) {