Unverified Commit fd54fa6e authored by Phillip Lougher's avatar Phillip Lougher Committed by Christian Brauner
Browse files

Squashfs: Rewrite and update squashfs_readahead_fragment() to not use page->index 



The previous implementation lacked error checking (e.g. the bytes
returned by squashfs_fill_page() is not checked), and the use of
page->index could not be removed without substantially rewriting
the routine to use the page actor abstraction used elsewhere.

Signed-off-by: default avatarPhillip Lougher <phillip@squashfs.org.uk>
Link: https://lore.kernel.org/r/20240818235847.170468-5-phillip@squashfs.org.uk


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 7f73fcde

fs/squashfs/file.c

+50 −16
Original line number Diff line number Diff line
@@ -494,39 +494,73 @@ static int squashfs_read_folio(struct file *file, struct folio *folio) 
}



static int squashfs_readahead_fragment(struct page **page,

	unsigned int pages, unsigned int expected)

	unsigned int pages, unsigned int expected, loff_t start)

{

	struct inode *inode = page[0]->mapping->host;

	struct squashfs_cache_entry *buffer = squashfs_get_fragment(inode->i_sb,

		squashfs_i(inode)->fragment_block,

		squashfs_i(inode)->fragment_size);

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

	unsigned int n, mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;

	int error = buffer->error;

	int i, bytes, copied;

	struct squashfs_page_actor *actor;

	unsigned int offset;

	void *addr;

	struct page *last_page;



	if (buffer->error)

		goto out;



	if (error)

	actor = squashfs_page_actor_init_special(msblk, page, pages,

							expected, start);

	if (!actor)

		goto out;



	expected += squashfs_i(inode)->fragment_offset;

	squashfs_actor_nobuff(actor);

	addr = squashfs_first_page(actor);



	for (copied = offset = 0; offset < expected; offset += PAGE_SIZE) {

		int avail = min_t(int, expected - offset, PAGE_SIZE);



		if (!IS_ERR(addr)) {

			bytes = squashfs_copy_data(addr, buffer, offset +

					squashfs_i(inode)->fragment_offset, avail);



			if (bytes != avail)

				goto failed;

		}



		copied += avail;

		addr = squashfs_next_page(actor);

	}



	for (n = 0; n < pages; n++) {

		unsigned int base = (page[n]->index & mask) << PAGE_SHIFT;

		unsigned int offset = base + squashfs_i(inode)->fragment_offset;

	last_page = squashfs_page_actor_free(actor);



		if (expected > offset) {

			unsigned int avail = min_t(unsigned int, expected -

				offset, PAGE_SIZE);

	if (copied == expected) {

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

		bytes = copied % PAGE_SIZE;

		if (bytes && last_page)

			memzero_page(last_page, bytes, PAGE_SIZE - bytes);



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

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

			flush_dcache_page(page[i]);

			SetPageUptodate(page[i]);

		}

	}



		unlock_page(page[n]);

		put_page(page[n]);

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

		unlock_page(page[i]);

		put_page(page[i]);

	}



	squashfs_cache_put(buffer);

	return 0;



failed:

	squashfs_page_actor_free(actor);



out:

	squashfs_cache_put(buffer);

	return error;

	return 1;

}



static void squashfs_readahead(struct readahead_control *ractl)
@@ -572,7 +606,7 @@ static void squashfs_readahead(struct readahead_control *ractl) 
		if (start >> msblk->block_log == file_end &&

				squashfs_i(inode)->fragment_block != SQUASHFS_INVALID_BLK) {

			res = squashfs_readahead_fragment(pages, nr_pages,

							  expected);

							  expected, start);

			if (res)

				goto skip_pages;

			continue;