On Wed, May 30, 2018 at 11:58:11AM +0200, Christoph Hellwig wrote:
> Simply use iomap_apply to iterate over the file and a submit a bio for
> each non-uptodate but mapped region and zero everything else. Note that
> as-is this can not be used for file systems with a blocksize smaller than
> the page size, but that support will be added later.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/iomap.c | 203 +++++++++++++++++++++++++++++++++++++++++-
> include/linux/iomap.h | 4 +
> 2 files changed, 206 insertions(+), 1 deletion(-)
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index b0bc928672af..5e5a266e3325 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -1,6 +1,6 @@
> /*
> * Copyright (C) 2010 Red Hat, Inc.
> - * Copyright (c) 2016 Christoph Hellwig.
> + * Copyright (c) 2016-2018 Christoph Hellwig.
> *
> * This program is free software; you can redistribute it and/or modify it
> * under the terms and conditions of the GNU General Public License,
> @@ -18,6 +18,7 @@
> #include <linux/uaccess.h>
> #include <linux/gfp.h>
> #include <linux/mm.h>
> +#include <linux/mm_inline.h>
> #include <linux/swap.h>
> #include <linux/pagemap.h>
> #include <linux/file.h>
> @@ -102,6 +103,206 @@ iomap_sector(struct iomap *iomap, loff_t pos)
> return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT;
> }
>
> +static void
> +iomap_read_end_io(struct bio *bio)
> +{
> + int error = blk_status_to_errno(bio->bi_status);
> + struct bio_vec *bvec;
> + int i;
> +
> + bio_for_each_segment_all(bvec, bio, i)
> + page_endio(bvec->bv_page, false, error);
> + bio_put(bio);
> +}
> +
> +struct iomap_readpage_ctx {
> + struct page *cur_page;
> + bool cur_page_in_bio;
> + bool is_readahead;
> + struct bio *bio;
> + struct list_head *pages;
> +};
> +
> +static loff_t
> +iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> + struct iomap *iomap)
> +{
> + struct iomap_readpage_ctx *ctx = data;
> + struct page *page = ctx->cur_page;
> + unsigned poff = pos & (PAGE_SIZE - 1);
> + unsigned plen = min_t(loff_t, PAGE_SIZE - poff, length);
> + bool is_contig = false;
> + sector_t sector;
> +
> + /* we don't support blocksize < PAGE_SIZE quite yet: */
sentence ends with a ".". :)
> + WARN_ON_ONCE(pos != page_offset(page));
> + WARN_ON_ONCE(plen != PAGE_SIZE);
> +
> + if (iomap->type != IOMAP_MAPPED || pos >= i_size_read(inode)) {
In what situation do we get a read request completely beyond EOF?
(comment, please!)
> + zero_user(page, poff, plen);
> + SetPageUptodate(page);
> + goto done;
> + }
[...]
> +int
> +iomap_readpage(struct page *page, const struct iomap_ops *ops)
> +{
> + struct iomap_readpage_ctx ctx = { .cur_page = page };
> + struct inode *inode = page->mapping->host;
> + unsigned poff;
> + loff_t ret;
> +
> + WARN_ON_ONCE(page_has_buffers(page));
> +
> + for (poff = 0; poff < PAGE_SIZE; poff += ret) {
> + ret = iomap_apply(inode, page_offset(page) + poff,
> + PAGE_SIZE - poff, 0, ops, &ctx,
> + iomap_readpage_actor);
> + if (ret <= 0) {
> + WARN_ON_ONCE(ret == 0);
> + SetPageError(page);
> + break;
> + }
> + }
> +
> + if (ctx.bio) {
> + submit_bio(ctx.bio);
> + WARN_ON_ONCE(!ctx.cur_page_in_bio);
> + } else {
> + WARN_ON_ONCE(ctx.cur_page_in_bio);
> + unlock_page(page);
> + }
> + return 0;
Hmmm. If we had an error from iomap_apply, shouldn't we be returning
it here instead just throwing it away? some ->readpage callers
appear to ignore the PageError() state on return but do expect
errors to be returned.
[...]
> +iomap_readpages(struct address_space *mapping, struct list_head *pages,
> + unsigned nr_pages, const struct iomap_ops *ops)
> +{
> + struct iomap_readpage_ctx ctx = {
> + .pages = pages,
> + .is_readahead = true,
> + };
> + loff_t pos = page_offset(list_entry(pages->prev, struct page, lru));
> + loff_t last = page_offset(list_entry(pages->next, struct page, lru));
> + loff_t length = last - pos + PAGE_SIZE, ret = 0;
Two lines, please.
> + while (length > 0) {
> + ret = iomap_apply(mapping->host, pos, length, 0, ops,
> + &ctx, iomap_readpages_actor);
> + if (ret <= 0) {
> + WARN_ON_ONCE(ret == 0);
> + goto done;
> + }
> + pos += ret;
> + length -= ret;
> + }
> + ret = 0;
> +done:
> + if (ctx.bio)
> + submit_bio(ctx.bio);
> + if (ctx.cur_page) {
> + if (!ctx.cur_page_in_bio)
> + unlock_page(ctx.cur_page);
> + put_page(ctx.cur_page);
> + }
> + WARN_ON_ONCE(!ret && !list_empty(ctx.pages));
What error condition is this warning about?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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