Commit 8fc78b6f authored by Hsin-Yi Wang's avatar Hsin-Yi Wang Committed by Andrew Morton
Browse files

squashfs: implement readahead 

Implement readahead callback for squashfs.  It will read datablocks which
cover pages in readahead request.  For a few cases it will not mark page
as uptodate, including:

- file end is 0.
- zero filled blocks.
- current batch of pages isn't in the same datablock.
- decompressor error.

Otherwise pages will be marked as uptodate.  The unhandled pages will be
updated by readpage later.

Link: https://lkml.kernel.org/r/20220617083810.337573-4-hsinyi@chromium.org


Signed-off-by: default avatarHsin-Yi Wang <hsinyi@chromium.org>
Suggested-by: default avatarMatthew Wilcox <willy@infradead.org>
Reported-by: default avatarMatthew Wilcox <willy@infradead.org>
Reported-by: default avatarPhillip Lougher <phillip@squashfs.org.uk>
Reported-by: default avatarXiongwei Song <Xiongwei.Song@windriver.com>
Reported-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Hou Tao <houtao1@huawei.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Miao Xie <miaoxie@huawei.com>
Cc: Zhang Yi <yi.zhang@huawei.com>
Cc: Zheng Liang <zhengliang6@huawei.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent db98b430

fs/squashfs/file.c

+91 −1
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ 
#include "squashfs_fs_sb.h"

#include "squashfs_fs_i.h"

#include "squashfs.h"

#include "page_actor.h"



/*

 * Locate cache slot in range [offset, index] for specified inode.  If
@@ -495,7 +496,96 @@ static int squashfs_read_folio(struct file *file, struct folio *folio) 
	return 0;

}



static void squashfs_readahead(struct readahead_control *ractl)

{

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

	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;

	size_t mask = (1UL << msblk->block_log) - 1;

	unsigned short shift = msblk->block_log - PAGE_SHIFT;

	loff_t start = readahead_pos(ractl) & ~mask;

	size_t len = readahead_length(ractl) + readahead_pos(ractl) - start;

	struct squashfs_page_actor *actor;

	unsigned int nr_pages = 0;

	struct page **pages;

	int i, file_end = i_size_read(inode) >> msblk->block_log;

	unsigned int max_pages = 1UL << shift;



	readahead_expand(ractl, start, (len | mask) + 1);



	if (file_end == 0)

		return;



	pages = kmalloc_array(max_pages, sizeof(void *), GFP_KERNEL);

	if (!pages)

		return;



	for (;;) {

		pgoff_t index;

		int res, bsize;

		u64 block = 0;

		unsigned int expected;



		nr_pages = __readahead_batch(ractl, pages, max_pages);

		if (!nr_pages)

			break;



		if (readahead_pos(ractl) >= i_size_read(inode))

			goto skip_pages;



		index = pages[0]->index >> shift;

		if ((pages[nr_pages - 1]->index >> shift) != index)

			goto skip_pages;



		expected = index == file_end ?

			   (i_size_read(inode) & (msblk->block_size - 1)) :

			    msblk->block_size;



		bsize = read_blocklist(inode, index, &block);

		if (bsize == 0)

			goto skip_pages;



		actor = squashfs_page_actor_init_special(msblk, pages, nr_pages,

							 expected);

		if (!actor)

			goto skip_pages;



		res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);



		kfree(actor);



		if (res == expected) {

			int bytes;



			/* Last page (if present) may have trailing bytes not filled */

			bytes = res % PAGE_SIZE;

			if (pages[nr_pages - 1]->index == file_end && bytes)

				memzero_page(pages[nr_pages - 1], bytes,

					     PAGE_SIZE - bytes);



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

				flush_dcache_page(pages[i]);

				SetPageUptodate(pages[i]);

			}

		}



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

			unlock_page(pages[i]);

			put_page(pages[i]);

		}

	}



	kfree(pages);

	return;



skip_pages:

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

		unlock_page(pages[i]);

		put_page(pages[i]);

	}

	kfree(pages);

}



const struct address_space_operations squashfs_aops = {

	.read_folio = squashfs_read_folio

	.read_folio = squashfs_read_folio,

	.readahead = squashfs_readahead

};