mirros/rockchip-kernel
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

mm: introduce ->swap_rw and use it for reads from SWP_FS_OPS swap-space

Browse Source 
swap currently uses ->readpage to read swap pages.  This can only request
one page at a time from the filesystem, which is not most efficient.

swap uses ->direct_IO for writes which while this is adequate is an
inappropriate over-loading.  ->direct_IO may need to had handle allocate
space for holes or other details that are not relevant for swap.

So this patch introduces a new address_space operation: ->swap_rw.  In
this patch it is used for reads, and a subsequent patch will switch writes
to use it.

No filesystem yet supports ->swap_rw, but that is not a problem because
no filesystem actually works with filesystem-based swap.
Only two filesystems set SWP_FS_OPS:
- cifs sets the flag, but ->direct_IO always fails so swap cannot work.
- nfs sets the flag, but ->direct_IO calls generic_write_checks()
  which has failed on swap files for several releases.

To ensure that a NULL ->swap_rw isn't called, ->activate_swap() for both
NFS and cifs are changed to fail if ->swap_rw is not set.  This can be
removed if/when the function is added.

Future patches will restore swap-over-NFS functionality.

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 we create a mempool to provide the structures.

Link: https://lkml.kernel.org/r/164859778125.29473.13430559328221330589.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 d791ea676b
commit e1209d3a7a
6 changed files with 77 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

68
mm/page_io.c
View File

@@ -235,6 +235,25 @@ 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) {
mempool_t *pool = mempool_create_kmalloc_pool(
SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
if (cmpxchg(&sio_pool, NULL, pool))
mempool_destroy(pool);
}
if (!sio_pool)
return -ENOMEM;
return 0;
}
int __swap_writepage(struct page *page, struct writeback_control *wbc,
bio_end_io_t end_write_func)
{
@@ -306,6 +325,48 @@ 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);
}
static int swap_readpage_fs(struct page *page)
{
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;
struct swap_iocb *sio;
loff_t pos = page_file_offset(page);
int ret;
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);
return ret;
}
int swap_readpage(struct page *page, bool synchronous)
{
struct bio *bio;
@@ -334,12 +395,7 @@ 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;
ret = mapping->a_ops->readpage(swap_file, page);
if (!ret)
count_vm_event(PSWPIN);
ret = swap_readpage_fs(page);
goto out;
}