Commit 357c1206 authored by Jens Axboe's avatar Jens Axboe Committed by Linus Torvalds
Browse files

mpage: add argument structure for do_mpage_readpage() 

Patch series "Submit ->readpages() IO as read-ahead", v4.

The only caller of ->readpages() is from read-ahead, yet we don't submit
IO flagged with REQ_RAHEAD.  This means we don't see it in blktrace, for
instance, which is a shame.  Additionally, it's preventing further
functional changes in the block layer for deadling with read-ahead more
intelligently.  We already make assumptions about ->readpages() just
being for read-ahead in the mpage implementation, using
readahead_gfp_mask(mapping) as out GFP mask of choice.

This small series fixes up mpage_readpages() to submit with REQ_RAHEAD,
which takes care of file systems using mpage_readpages().  The first
patch is a prep patch, that makes do_mpage_readpage() take an argument
structure.

This patch (of 4):

We're currently passing 8 arguments to this function, clean it up a bit
by packing the arguments in an args structure we pass to it.

No intentional functional changes in this patch.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20180621010725.17813-2-axboe@kernel.dk


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <clm@fb.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 87aa7529

fs/mpage.c

+57 −52
Original line number Diff line number Diff line
@@ -133,6 +133,17 @@ map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) 
	} while (page_bh != head);

}



struct mpage_readpage_args {

	struct bio *bio;

	struct page *page;

	unsigned int nr_pages;

	sector_t last_block_in_bio;

	struct buffer_head map_bh;

	unsigned long first_logical_block;

	get_block_t *get_block;

	gfp_t gfp;

};



/*

 * This is the worker routine which does all the work of mapping the disk

 * blocks and constructs largest possible bios, submits them for IO if the
@@ -142,16 +153,14 @@ map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) 
 * represent the validity of its disk mapping and to decide when to do the next

 * get_block() call.

 */

static struct bio *

do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,

		sector_t *last_block_in_bio, struct buffer_head *map_bh,

		unsigned long *first_logical_block, get_block_t get_block,

		gfp_t gfp)

static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)

{

	struct page *page = args->page;

	struct inode *inode = page->mapping->host;

	const unsigned blkbits = inode->i_blkbits;

	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;

	const unsigned blocksize = 1 << blkbits;

	struct buffer_head *map_bh = &args->map_bh;

	sector_t block_in_file;

	sector_t last_block;

	sector_t last_block_in_file;
@@ -168,7 +177,7 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, 
		goto confused;



	block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);

	last_block = block_in_file + nr_pages * blocks_per_page;

	last_block = block_in_file + args->nr_pages * blocks_per_page;

	last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;

	if (last_block > last_block_in_file)

		last_block = last_block_in_file;
@@ -178,9 +187,10 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, 
	 * Map blocks using the result from the previous get_blocks call first.

	 */

	nblocks = map_bh->b_size >> blkbits;

	if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&

			block_in_file < (*first_logical_block + nblocks)) {

		unsigned map_offset = block_in_file - *first_logical_block;

	if (buffer_mapped(map_bh) &&

			block_in_file > args->first_logical_block &&

			block_in_file < (args->first_logical_block + nblocks)) {

		unsigned map_offset = block_in_file - args->first_logical_block;

		unsigned last = nblocks - map_offset;



		for (relative_block = 0; ; relative_block++) {
@@ -208,9 +218,9 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, 


		if (block_in_file < last_block) {

			map_bh->b_size = (last_block-block_in_file) << blkbits;

			if (get_block(inode, block_in_file, map_bh, 0))

			if (args->get_block(inode, block_in_file, map_bh, 0))

				goto confused;

			*first_logical_block = block_in_file;

			args->first_logical_block = block_in_file;

		}



		if (!buffer_mapped(map_bh)) {
@@ -273,43 +283,45 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, 
	/*

	 * This page will go to BIO.  Do we need to send this BIO off first?

	 */

	if (bio && (*last_block_in_bio != blocks[0] - 1))

		bio = mpage_bio_submit(REQ_OP_READ, 0, bio);

	if (args->bio && (args->last_block_in_bio != blocks[0] - 1))

		args->bio = mpage_bio_submit(REQ_OP_READ, 0, args->bio);



alloc_new:

	if (bio == NULL) {

	if (args->bio == NULL) {

		if (first_hole == blocks_per_page) {

			if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9),

								page))

				goto out;

		}

		bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),

				min_t(int, nr_pages, BIO_MAX_PAGES), gfp);

		if (bio == NULL)

		args->bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),

					min_t(int, args->nr_pages,

					      BIO_MAX_PAGES),

					args->gfp);

		if (args->bio == NULL)

			goto confused;

	}



	length = first_hole << blkbits;

	if (bio_add_page(bio, page, length, 0) < length) {

		bio = mpage_bio_submit(REQ_OP_READ, 0, bio);

	if (bio_add_page(args->bio, page, length, 0) < length) {

		args->bio = mpage_bio_submit(REQ_OP_READ, 0, args->bio);

		goto alloc_new;

	}



	relative_block = block_in_file - *first_logical_block;

	relative_block = block_in_file - args->first_logical_block;

	nblocks = map_bh->b_size >> blkbits;

	if ((buffer_boundary(map_bh) && relative_block == nblocks) ||

	    (first_hole != blocks_per_page))

		bio = mpage_bio_submit(REQ_OP_READ, 0, bio);

		args->bio = mpage_bio_submit(REQ_OP_READ, 0, args->bio);

	else

		*last_block_in_bio = blocks[blocks_per_page - 1];

		args->last_block_in_bio = blocks[blocks_per_page - 1];

out:

	return bio;

	return args->bio;



confused:

	if (bio)

		bio = mpage_bio_submit(REQ_OP_READ, 0, bio);

	if (args->bio)

		args->bio = mpage_bio_submit(REQ_OP_READ, 0, args->bio);

	if (!PageUptodate(page))

	        block_read_full_page(page, get_block);

		block_read_full_page(page, args->get_block);

	else

		unlock_page(page);

	goto out;
@@ -363,15 +375,12 @@ int 
mpage_readpages(struct address_space *mapping, struct list_head *pages,

				unsigned nr_pages, get_block_t get_block)

{

	struct bio *bio = NULL;

	struct mpage_readpage_args args = {

		.get_block = get_block,

		.gfp = readahead_gfp_mask(mapping),

	};

	unsigned page_idx;

	sector_t last_block_in_bio = 0;

	struct buffer_head map_bh;

	unsigned long first_logical_block = 0;

	gfp_t gfp = readahead_gfp_mask(mapping);



	map_bh.b_state = 0;

	map_bh.b_size = 0;

	for (page_idx = 0; page_idx < nr_pages; page_idx++) {

		struct page *page = lru_to_page(pages);
@@ -379,18 +388,16 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages, 
		list_del(&page->lru);

		if (!add_to_page_cache_lru(page, mapping,

					page->index,

					gfp)) {

			bio = do_mpage_readpage(bio, page,

					nr_pages - page_idx,

					&last_block_in_bio, &map_bh,

					&first_logical_block,

					get_block, gfp);

					args.gfp)) {

			args.page = page;

			args.nr_pages = nr_pages - page_idx;

			args.bio = do_mpage_readpage(&args);

		}

		put_page(page);

	}

	BUG_ON(!list_empty(pages));

	if (bio)

		mpage_bio_submit(REQ_OP_READ, 0, bio);

	if (args.bio)

		mpage_bio_submit(REQ_OP_READ, 0, args.bio);

	return 0;

}

EXPORT_SYMBOL(mpage_readpages);
@@ -400,18 +407,16 @@ EXPORT_SYMBOL(mpage_readpages); 
 */

int mpage_readpage(struct page *page, get_block_t get_block)

{

	struct bio *bio = NULL;

	sector_t last_block_in_bio = 0;

	struct buffer_head map_bh;

	unsigned long first_logical_block = 0;

	gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);

	struct mpage_readpage_args args = {

		.page = page,

		.nr_pages = 1,

		.get_block = get_block,

		.gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL),

	};



	map_bh.b_state = 0;

	map_bh.b_size = 0;

	bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,

			&map_bh, &first_logical_block, get_block, gfp);

	if (bio)

		mpage_bio_submit(REQ_OP_READ, 0, bio);

	args.bio = do_mpage_readpage(&args);

	if (args.bio)

		mpage_bio_submit(REQ_OP_READ, 0, args.bio);

	return 0;

}

EXPORT_SYMBOL(mpage_readpage);

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