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

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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: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Andrew 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jens Axboe 2018-08-17 15:45:36 -07:00 committed by Linus Torvalds
parent 357c120652
commit 74c8164e1c
3 changed files with 28 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
fs/f2fs/data.c
View File

@ -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,

29
fs/mpage.c
View File

@ -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);

4
include/linux/fs.h
View File

@ -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);