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bio_vec-backed iov_iter

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New variant of iov_iter - ITER_BVEC in iter->type, backed with
bio_vec array instead of iovec one.  Primitives taught to deal
with such beasts, __swap_write() switched to using that kind
of iov_iter.

Note that bio_vec is just a <page, offset, length> triple - there's
nothing block-specific about it.  I've left the definition where it
was, but took it from under ifdef CONFIG_BLOCK.

Next target: ->splice_write()...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2014-04-04 23:12:29 -04:00
parent 81055e584f
commit 62a8067a7f
5 changed files with 385 additions and 44 deletions
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19
mm/page_io.c
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@ -259,23 +259,28 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
struct kiocb kiocb;
struct file *swap_file = sis->swap_file;
struct address_space *mapping = swap_file->f_mapping;
struct iovec iov = {
.iov_base = kmap(page),
.iov_len = PAGE_SIZE,
struct bio_vec bv = {
.bv_page = page,
.bv_len = PAGE_SIZE,
.bv_offset = 0
};
struct iov_iter from = {
.type = ITER_BVEC | WRITE,
.count = PAGE_SIZE,
.iov_offset = 0,
.nr_segs = 1,
.bvec = &bv
};
struct iov_iter from;
init_sync_kiocb(&kiocb, swap_file);
kiocb.ki_pos = page_file_offset(page);
kiocb.ki_nbytes = PAGE_SIZE;
iov_iter_init(&from, KERNEL_WRITE, &iov, 1, PAGE_SIZE);
set_page_writeback(page);
unlock_page(page);
ret = mapping->a_ops->direct_IO(KERNEL_WRITE,
ret = mapping->a_ops->direct_IO(ITER_BVEC | WRITE,
&kiocb, &from,
kiocb.ki_pos);
kunmap(page);
if (ret == PAGE_SIZE) {
count_vm_event(PSWPOUT);
ret = 0;