Commit 1bb1a07a authored by Phillip Lougher's avatar Phillip Lougher Committed by Andrew Morton
Browse files

squashfs: don't use intermediate buffer if pages missing 

Now that the "page actor" can handle missing pages, we don't have to fall
back to using an intermediate buffer in Squashfs_readpage_block() if all
the pages necessary can't be obtained.

Link: https://lkml.kernel.org/r/20220611032133.5743-3-phillip@squashfs.org.uk


Signed-off-by: default avatarPhillip Lougher <phillip@squashfs.org.uk>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Xiongwei Song <Xiongwei.Song@windriver.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f268eedd

fs/squashfs/file_direct.c

+12 −63
Original line number Diff line number Diff line
@@ -18,9 +18,6 @@ 
#include "squashfs.h"

#include "page_actor.h"



static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,

	int pages, struct page **page, int bytes);



/* Read separately compressed datablock directly into page cache */

int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,

	int expected)
@@ -33,7 +30,7 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize, 
	int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;

	int start_index = target_page->index & ~mask;

	int end_index = start_index | mask;

	int i, n, pages, missing_pages, bytes, res = -ENOMEM;

	int i, n, pages, bytes, res = -ENOMEM;

	struct page **page;

	struct squashfs_page_actor *actor;

	void *pageaddr;
@@ -48,44 +45,29 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize, 
		return res;



	/* Try to grab all the pages covered by the Squashfs block */

	for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) {

	for (i = 0, n = start_index; n <= end_index; n++) {

		page[i] = (n == target_page->index) ? target_page :

			grab_cache_page_nowait(target_page->mapping, n);



		if (page[i] == NULL) {

			missing_pages++;

		if (page[i] == NULL)

			continue;

		}



		if (PageUptodate(page[i])) {

			unlock_page(page[i]);

			put_page(page[i]);

			page[i] = NULL;

			missing_pages++;

		}

			continue;

		}



	if (missing_pages) {

		/*

		 * Couldn't get one or more pages, this page has either

		 * been VM reclaimed, but others are still in the page cache

		 * and uptodate, or we're racing with another thread in

		 * squashfs_readpage also trying to grab them.  Fall back to

		 * using an intermediate buffer.

		 */

		res = squashfs_read_cache(target_page, block, bsize, pages,

							page, expected);

		if (res < 0)

			goto mark_errored;



		goto out;

		i++;

	}



	pages = i;



	/*

	 * Create a "page actor" which will kmap and kunmap the

	 * page cache pages appropriately within the decompressor

	 */

	actor = squashfs_page_actor_init_special(msblk, page, pages, 0);

	actor = squashfs_page_actor_init_special(msblk, page, pages, expected);

	if (actor == NULL)

		goto out;
@@ -102,12 +84,12 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize, 
		goto mark_errored;

	}



	/* Last page may have trailing bytes not filled */

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

	bytes = res % PAGE_SIZE;

	if (bytes) {

		pageaddr = kmap_atomic(page[pages - 1]);

	if (page[pages - 1]->index == end_index && bytes) {

		pageaddr = kmap_local_page(page[pages - 1]);

		memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);

		kunmap_atomic(pageaddr);

		kunmap_local(pageaddr);

	}



	/* Mark pages as uptodate, unlock and release */
@@ -140,36 +122,3 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize, 
	kfree(page);

	return res;

}
 




static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,

	int pages, struct page **page, int bytes)

{

	struct inode *i = target_page->mapping->host;

	struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb,

						 block, bsize);

	int res = buffer->error, n, offset = 0;



	if (res) {

		ERROR("Unable to read page, block %llx, size %x\n", block,

			bsize);

		goto out;

	}



	for (n = 0; n < pages && bytes > 0; n++,

			bytes -= PAGE_SIZE, offset += PAGE_SIZE) {

		int avail = min_t(int, bytes, PAGE_SIZE);



		if (page[n] == NULL)

			continue;



		squashfs_fill_page(page[n], buffer, offset, avail);

		unlock_page(page[n]);

		if (page[n] != target_page)

			put_page(page[n]);

	}



out:

	squashfs_cache_put(buffer);

	return res;

}