Commit 74c8164e authored by Jens Axboe's avatar Jens Axboe Committed by Linus Torvalds
Browse files

mpage: mpage_readpages() should submit IO as read-ahead 

a_ops->readpages() is only ever used for read-ahead, yet we don't flag
the IO being submitted as such.  Fix that up.  Any file system that uses
mpage_readpages() as its ->readpages() implementation will now get this
right.

Since we're passing in whether the IO is read-ahead or not, we don't
need to pass in the 'gfp' separately, as it is dependent on the IO being
read-ahead.  Kill off that member.

Add some documentation notes on ->readpages() being purely for
read-ahead.

Link: http://lkml.kernel.org/r/20180621010725.17813-3-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: Chris Mason <clm@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 357c1206

fs/f2fs/data.c

+5 −0
Original line number Diff line number Diff line
@@ -1421,6 +1421,11 @@ out: 
/*

 * This function was originally taken from fs/mpage.c, and customized for f2fs.

 * Major change was from block_size == page_size in f2fs by default.

 *

 * Note that the aops->readpages() function is ONLY used for read-ahead. If

 * this function ever deviates from doing just read-ahead, it should either

 * use ->readpage() or do the necessary surgery to decouple ->readpages()

 * readom read-ahead.

 */

static int f2fs_mpage_readpages(struct address_space *mapping,

			struct list_head *pages, struct page *page,

fs/mpage.c

+19 −10
Original line number Diff line number Diff line
@@ -137,11 +137,11 @@ struct mpage_readpage_args { 
	struct bio *bio;

	struct page *page;

	unsigned int nr_pages;

	bool is_readahead;

	sector_t last_block_in_bio;

	struct buffer_head map_bh;

	unsigned long first_logical_block;

	get_block_t *get_block;

	gfp_t gfp;

};



/*
@@ -170,8 +170,18 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args) 
	struct block_device *bdev = NULL;

	int length;

	int fully_mapped = 1;

	int op_flags;

	unsigned nblocks;

	unsigned relative_block;

	gfp_t gfp;



	if (args->is_readahead) {

		op_flags = REQ_RAHEAD;

		gfp = readahead_gfp_mask(page->mapping);

	} else {

		op_flags = 0;

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

	}



	if (page_has_buffers(page))

		goto confused;
@@ -284,7 +294,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args) 
	 * This page will go to BIO.  Do we need to send this BIO off first?

	 */

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

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

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



alloc_new:

	if (args->bio == NULL) {
@@ -296,14 +306,14 @@ alloc_new: 
		args->bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),

					min_t(int, args->nr_pages,

					      BIO_MAX_PAGES),

					args->gfp);

					gfp);

		if (args->bio == NULL)

			goto confused;

	}



	length = first_hole << blkbits;

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

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

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

		goto alloc_new;

	}
@@ -311,7 +321,7 @@ alloc_new: 
	nblocks = map_bh->b_size >> blkbits;

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

	    (first_hole != blocks_per_page))

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

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

	else

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

out:
@@ -319,7 +329,7 @@ out: 


confused:

	if (args->bio)

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

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

	if (!PageUptodate(page))

		block_read_full_page(page, args->get_block);

	else
@@ -377,7 +387,7 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages, 
{

	struct mpage_readpage_args args = {

		.get_block = get_block,

		.gfp = readahead_gfp_mask(mapping),

		.is_readahead = true,

	};

	unsigned page_idx;
@@ -388,7 +398,7 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages, 
		list_del(&page->lru);

		if (!add_to_page_cache_lru(page, mapping,

					page->index,

					args.gfp)) {

					readahead_gfp_mask(mapping))) {

			args.page = page;

			args.nr_pages = nr_pages - page_idx;

			args.bio = do_mpage_readpage(&args);
@@ -397,7 +407,7 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages, 
	}

	BUG_ON(!list_empty(pages));

	if (args.bio)

		mpage_bio_submit(REQ_OP_READ, 0, args.bio);

		mpage_bio_submit(REQ_OP_READ, REQ_RAHEAD, args.bio);

	return 0;

}

EXPORT_SYMBOL(mpage_readpages);
@@ -411,7 +421,6 @@ int mpage_readpage(struct page *page, get_block_t get_block) 
		.page = page,

		.nr_pages = 1,

		.get_block = get_block,

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

	};



	args.bio = do_mpage_readpage(&args);

include/linux/fs.h

+4 −0
Original line number Diff line number Diff line
@@ -344,6 +344,10 @@ struct address_space_operations { 
	/* Set a page dirty.  Return true if this dirtied it */

	int (*set_page_dirty)(struct page *page);



	/*

	 * Reads in the requested pages. Unlike ->readpage(), this is

	 * PURELY used for read-ahead!.

	 */

	int (*readpages)(struct file *filp, struct address_space *mapping,

			struct list_head *pages, unsigned nr_pages);

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