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Commit adb33b84 authored by Paul Lawrence's avatar Paul Lawrence
Browse files

ANDROID: Incremental fs: Avoid continually recalculating hashes 



With a verified file (use incfs_perf to create a verified file), throughput
measured using dd after dropping caches increases from 200M/s to 290M/s

Test: incfs_test passes
Bug: 155996534
Signed-off-by: default avatarPaul Lawrence <paullawrence@google.com>
Change-Id: I7abb5ad92e4167f82f3452acc9db322fec8307dd
parent cf38436c

fs/incfs/data_mgmt.c

+70 −10
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#include <linux/file.h>

#include <linux/ktime.h>

#include <linux/mm.h>

#include <linux/pagemap.h>

#include <linux/lz4.h>

#include <linux/crc32.h>
@@ -366,7 +367,8 @@ static void log_block_read(struct mount_info *mi, incfs_uuid_t *id, 
}



static int validate_hash_tree(struct file *bf, struct data_file *df,

			      int block_index, struct mem_range data, u8 *buf)

			      int block_index, struct mem_range data,

			      u8 *tmp_buf)

{

	u8 digest[INCFS_MAX_HASH_SIZE] = {};

	struct mtree *tree = NULL;
@@ -379,6 +381,7 @@ static int validate_hash_tree(struct file *bf, struct data_file *df, 
	int hash_per_block;

	int lvl = 0;

	int res;

	struct page *saved_page = NULL;



	tree = df->df_hash_tree;

	sig = df->df_signature;
@@ -400,17 +403,39 @@ static int validate_hash_tree(struct file *bf, struct data_file *df, 
				INCFS_DATA_FILE_BLOCK_SIZE);

		size_t hash_off_in_block = hash_block_index * digest_size

			% INCFS_DATA_FILE_BLOCK_SIZE;

		struct mem_range buf_range = range(buf,

					INCFS_DATA_FILE_BLOCK_SIZE);

		ssize_t read_res = incfs_kread(bf, buf,

				INCFS_DATA_FILE_BLOCK_SIZE, hash_block_off);

		struct mem_range buf_range;

		struct page *page = NULL;

		bool aligned = (hash_block_off &

				(INCFS_DATA_FILE_BLOCK_SIZE - 1)) == 0;

		u8 *actual_buf;



		if (aligned) {

			page = read_mapping_page(

				bf->f_inode->i_mapping,

				hash_block_off / INCFS_DATA_FILE_BLOCK_SIZE,

				NULL);



			if (IS_ERR(page))

				return PTR_ERR(page);



			actual_buf = page_address(page);

		} else {

			size_t read_res =

				incfs_kread(bf, tmp_buf,

					    INCFS_DATA_FILE_BLOCK_SIZE,

					    hash_block_off);



			if (read_res < 0)

				return read_res;

			if (read_res != INCFS_DATA_FILE_BLOCK_SIZE)

				return -EIO;



		saved_digest_rng = range(buf + hash_off_in_block, digest_size);

			actual_buf = tmp_buf;

		}



		buf_range = range(actual_buf, INCFS_DATA_FILE_BLOCK_SIZE);

		saved_digest_rng =

			range(actual_buf + hash_off_in_block, digest_size);

		if (!incfs_equal_ranges(calc_digest_rng, saved_digest_rng)) {

			int i;

			bool zero = true;
@@ -425,9 +450,37 @@ static int validate_hash_tree(struct file *bf, struct data_file *df, 


			if (zero)

				pr_debug("incfs: Note saved_digest all zero - did you forget to load the hashes?\n");



			if (saved_page)

				put_page(saved_page);

			if (page)

				put_page(page);

			return -EBADMSG;

		}



		if (saved_page) {

			/*

			 * This is something of a kludge. The PageChecked flag

			 * is reserved for the file system, but we are setting

			 * this on the pages belonging to the underlying file

			 * system. incfs is only going to be used on f2fs and

			 * ext4 which only use this flag when fs-verity is being

			 * used, so this is safe for now, however a better

			 * mechanism needs to be found.

			 */

			SetPageChecked(saved_page);

			put_page(saved_page);

			saved_page = NULL;

		}



		if (page && PageChecked(page)) {

			put_page(page);

			return 0;

		}



		saved_page = page;

		page = NULL;



		res = incfs_calc_digest(tree->alg, buf_range, calc_digest_rng);

		if (res)

			return res;
@@ -437,8 +490,15 @@ static int validate_hash_tree(struct file *bf, struct data_file *df, 
	root_hash_rng = range(tree->root_hash, digest_size);

	if (!incfs_equal_ranges(calc_digest_rng, root_hash_rng)) {

		pr_debug("incfs: Root hash mismatch blk:%d\n", block_index);

		if (saved_page)

			put_page(saved_page);

		return -EBADMSG;

	}



	if (saved_page) {

		SetPageChecked(saved_page);

		put_page(saved_page);

	}

	return 0;

}