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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 /fs/cifs
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 'fs/cifs')
-rw-r--r--fs/cifs/file.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 14d29404c834..794e2cc23e3f 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4905,6 +4905,10 @@ static int cifs_swap_activate(struct swap_info_struct *sis,
cifs_dbg(FYI, "swap activate\n");
+ if (!swap_file->f_mapping->a_ops->swap_rw)
+ /* Cannot support swap */
+ return -EINVAL;
+
spin_lock(&inode->i_lock);
blocks = inode->i_blocks;
isize = inode->i_size;