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authorNeilBrown <neilb@suse.de>2022-05-10 04:20:48 +0300
committerakpm <akpm@linux-foundation.org>2022-05-10 04:20:48 +0300
commite1209d3a7a67c281260ba9989621060ba7328b8c (patch)
tree267b9e527bf7d26db3078fd32ce60447b8e45108 /mm/swapfile.c
parentd791ea676b66489ef6dabd04cd655f5c77426e40 (diff)
downloadlinux-e1209d3a7a67c281260ba9989621060ba7328b8c.tar.xz
mm: introduce ->swap_rw and use it for reads from SWP_FS_OPS swap-space
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>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index d811458c0a88..9398e915b36b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2262,6 +2262,11 @@ 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;
}