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Subject[PATCH 03/18] MM: use ->swap_rw for reads from SWP_FS_OPS swap-space
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To submit an async read with ->swap_rw() we need to allocate
a structure to hold the kiocb and other details. swap_readpage() cannot
handle transient failure, so create a mempool to provide the structures.

Signed-off-by: NeilBrown <neilb@suse.de>
---
mm/page_io.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++------
mm/swap.h | 1 +
mm/swapfile.c | 5 +++++
3 files changed, 58 insertions(+), 6 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index a9fe5de5dc32..47d7e7866e33 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -283,6 +283,23 @@ static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
#define bio_associate_blkg_from_page(bio, page) do { } while (0)
#endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */

+struct swap_iocb {
+ struct kiocb iocb;
+ struct bio_vec bvec;
+};
+static mempool_t *sio_pool;
+
+int sio_pool_init(void)
+{
+ if (!sio_pool)
+ sio_pool = mempool_create_kmalloc_pool(
+ SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
+ if (sio_pool)
+ return 0;
+ else
+ return -ENOMEM;
+}
+
int __swap_writepage(struct page *page, struct writeback_control *wbc,
bio_end_io_t end_write_func)
{
@@ -353,6 +370,23 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
return 0;
}

+static void sio_read_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 != 0 && ret != PAGE_SIZE) {
+ SetPageError(page);
+ ClearPageUptodate(page);
+ pr_alert_ratelimited("Read-error on swap-device\n");
+ } else {
+ SetPageUptodate(page);
+ count_vm_event(PSWPIN);
+ }
+ unlock_page(page);
+ mempool_free(sio, sio_pool);
+}
+
int swap_readpage(struct page *page, bool synchronous)
{
struct bio *bio;
@@ -378,13 +412,25 @@ int swap_readpage(struct page *page, bool synchronous)
}

if (data_race(sis->flags & SWP_FS_OPS)) {
- //struct file *swap_file = sis->swap_file;
- //struct address_space *mapping = swap_file->f_mapping;
+ struct file *swap_file = sis->swap_file;
+ struct address_space *mapping = swap_file->f_mapping;
+ struct iov_iter from;
+ struct swap_iocb *sio;
+ loff_t pos = page_file_offset(page);
+
+ sio = mempool_alloc(sio_pool, GFP_KERNEL);
+ init_sync_kiocb(&sio->iocb, swap_file);
+ sio->iocb.ki_pos = pos;
+ sio->iocb.ki_complete = sio_read_complete;
+ sio->bvec.bv_page = page;
+ sio->bvec.bv_len = PAGE_SIZE;
+ sio->bvec.bv_offset = 0;
+
+ iov_iter_bvec(&from, READ, &sio->bvec, 1, PAGE_SIZE);
+ ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
+ if (ret != -EIOCBQUEUED)
+ sio_read_complete(&sio->iocb, ret);

- /* This needs to use ->swap_rw() */
- ret = -EINVAL;
- if (!ret)
- count_vm_event(PSWPIN);
goto out;
}

diff --git a/mm/swap.h b/mm/swap.h
index 13e72a5023aa..128a1d3e5558 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -3,6 +3,7 @@
#include <linux/blk_types.h> /* for bio_end_io_t */

/* linux/mm/page_io.c */
+int sio_pool_init(void);
int swap_readpage(struct page *page, bool do_poll);
int swap_writepage(struct page *page, struct writeback_control *wbc);
void end_swap_bio_write(struct bio *bio);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f23d9ff21cf8..43539be38e68 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2401,6 +2401,11 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
if (ret < 0)
return ret;
sis->flags |= SWP_ACTIVATED;
+ if ((sis->flags & SWP_FS_OPS) &&
+ sio_pool_init() != 0) {
+ destroy_swap_extents(sis);
+ return -ENOMEM;
+ }
return ret;
}


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