Using ->direct_IO and ->readpage for the generic swap file
infrastructure requires all sorts of nasty workarounds. ->readpage
implementations don't play nicely with swap cache pages, and ->direct_IO
implementations have different locking conventions for every filesystem.
Instead, use ->read_iter/->write_iter with an ITER_BVEC and let the
filesystem take care of it. This will also allow us to easily transition
to kernel AIO if that gets merged in the future.
Cc: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Omar Sandoval <osandov@xxxxxxxxxxx>
---
mm/page_io.c | 30 +++++++++++++++++++++++-------
mm/swapfile.c | 11 ++++++++++-
2 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/mm/page_io.c b/mm/page_io.c
index 532a39b..61165b0 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -263,7 +263,6 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
if (sis->flags & SWP_FILE) {
struct kiocb kiocb;
struct file *swap_file = sis->swap_file;
- struct address_space *mapping = swap_file->f_mapping;
struct iov_iter from;
struct bio_vec bv = {
.bv_page = page,
@@ -279,9 +278,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
set_page_writeback(page);
unlock_page(page);
- ret = mapping->a_ops->direct_IO(ITER_BVEC | WRITE,
- &kiocb, &from,
- kiocb.ki_pos);
+ ret = swap_file->f_op->write_iter(&kiocb, &from);
if (ret == PAGE_SIZE) {
count_vm_event(PSWPOUT);
ret = 0;
@@ -344,12 +341,31 @@ int swap_readpage(struct page *page)
}
if (sis->flags & SWP_FILE) {
+ struct kiocb kiocb;
struct file *swap_file = sis->swap_file;
- struct address_space *mapping = swap_file->f_mapping;
+ struct iov_iter to;
+ struct bio_vec bv = {
+ .bv_page = page,
+ .bv_len = PAGE_SIZE,
+ .bv_offset = 0,
+ };
+
+ iov_iter_bvec(&to, ITER_BVEC | READ, &bv, 1, PAGE_SIZE);
+
+ init_sync_kiocb(&kiocb, swap_file);
+ kiocb.ki_pos = page_file_offset(page);
+ kiocb.ki_nbytes = PAGE_SIZE;
- ret = mapping->a_ops->readpage(swap_file, page);
- if (!ret)
+ ret = swap_file->f_op->read_iter(&kiocb, &to);
+ if (ret == PAGE_SIZE) {
+ SetPageUptodate(page);
count_vm_event(PSWPIN);
+ ret = 0;
+ } else {
+ ClearPageUptodate(page);
+ SetPageError(page);
+ }
+ unlock_page(page);
return ret;
}
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 63f55cc..4e14122 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2379,7 +2379,16 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
name = NULL;
goto bad_swap;
}
- swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
+ swap_file = file_open_name(name, O_RDWR | O_LARGEFILE | O_DIRECT, 0);
+ if (swap_file == ERR_PTR(-EINVAL)) {
+ /*
+ * XXX: there are several filesystems that implement ->bmap but
+ * not ->direct_IO. It's unlikely that anyone is using a
+ * swapfile on, e.g., the MINIX fs, but this kludge will keep us
+ * from getting a complaint from the one person who does.
+ */
+ swap_file = file_open_name(name, O_RDWR | O_LARGEFILE, 0);
+ }
if (IS_ERR(swap_file)) {
error = PTR_ERR(swap_file);
swap_file = NULL;
--
2.2.1
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