1 files changed, 386 insertions, 0 deletions

diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
new file mode 100644
index 000000000..c7b6cdb2e
--- /dev/null
+++ b/fs/ext4/readpage.c
@@ -0,0 +1,386 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/ext4/readpage.c
+ *
+ * Copyright (C) 2002, Linus Torvalds.
+ * Copyright (C) 2015, Google, Inc.
+ *
+ * This was originally taken from fs/mpage.c
+ *
+ * The ext4_mpage_readpages() function here is intended to
+ * replace mpage_readahead() in the general case, not just for
+ * encrypted files.  It has some limitations (see below), where it
+ * will fall back to read_block_full_page(), but these limitations
+ * should only be hit when page_size != block_size.
+ *
+ * This will allow us to attach a callback function to support ext4
+ * encryption.
+ *
+ * If anything unusual happens, such as:
+ *
+ * - encountering a page which has buffers
+ * - encountering a page which has a non-hole after a hole
+ * - encountering a page with non-contiguous blocks
+ *
+ * then this code just gives up and calls the buffer_head-based read function.
+ * It does handle a page which has holes at the end - that is a common case:
+ * the end-of-file on blocksize < PAGE_SIZE setups.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/kdev_t.h>
+#include <linux/gfp.h>
+#include <linux/bio.h>
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/blk-crypto.h>
+#include <linux/blkdev.h>
+#include <linux/highmem.h>
+#include <linux/prefetch.h>
+#include <linux/mpage.h>
+#include <linux/writeback.h>
+#include <linux/backing-dev.h>
+
+#include "ext4.h"
+#include <trace/events/ext4.h>
+
+#define NUM_VERITY_WORKS 128
+
+static struct kmem_cache *ext4_verity_work_cache;
+static mempool_t *ext4_verity_work_pool;
+
+struct ext4_verity_work {
+	struct bio *bio;
+	struct fsverity_info *vi;
+	struct work_struct work;
+};
+
+static void __read_end_io(struct bio *bio)
+{
+	struct folio_iter fi;
+
+	bio_for_each_folio_all(fi, bio)
+		folio_end_read(fi.folio, bio->bi_status == 0);
+	if (bio->bi_private)
+		mempool_free(bio->bi_private, ext4_verity_work_pool);
+	bio_put(bio);
+}
+
+static void verity_work(struct work_struct *work)
+{
+	struct ext4_verity_work *ctx =
+		container_of(work, struct ext4_verity_work, work);
+	struct bio *bio = ctx->bio;
+	struct fsverity_info *vi = ctx->vi;
+
+	/*
+	 * Free the ext4_verity_work right away, since it's no longer needed.
+	 * This relieves the pressure on the mempool as much as possible.
+	 */
+	mempool_free(ctx, ext4_verity_work_pool);
+	bio->bi_private = NULL;
+
+	fsverity_verify_bio(vi, bio);
+
+	__read_end_io(bio);
+}
+
+/*
+ * I/O completion handler for multipage BIOs.
+ *
+ * The mpage code never puts partial pages into a BIO (except for end-of-file).
+ * If a page does not map to a contiguous run of blocks then it simply falls
+ * back to block_read_full_folio().
+ *
+ * Why is this?  If a page's completion depends on a number of different BIOs
+ * which can complete in any order (or at the same time) then determining the
+ * status of that page is hard.  See end_buffer_async_read() for the details.
+ * There is no point in duplicating all that complexity.
+ */
+static void mpage_end_io(struct bio *bio)
+{
+	if (IS_ENABLED(CONFIG_FS_VERITY) && bio->bi_private &&
+	    !bio->bi_status) {
+		struct ext4_verity_work *ctx = bio->bi_private;
+
+		INIT_WORK(&ctx->work, verity_work);
+		fsverity_enqueue_verify_work(&ctx->work);
+		return;
+	}
+	__read_end_io(bio);
+}
+
+static void ext4_set_verity_work(struct bio *bio, struct fsverity_info *vi)
+{
+	if (vi) {
+		/* Due to the mempool, this never fails. */
+		struct ext4_verity_work *ctx =
+			mempool_alloc(ext4_verity_work_pool, GFP_NOFS);
+
+		ctx->bio = bio;
+		ctx->vi = vi;
+		bio->bi_private = ctx;
+	}
+}
+
+static inline loff_t ext4_readpage_limit(struct inode *inode)
+{
+	if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
+		return inode->i_sb->s_maxbytes;
+
+	return i_size_read(inode);
+}
+
+static int ext4_mpage_readpages(struct inode *inode, struct fsverity_info *vi,
+		struct readahead_control *rac, struct folio *folio)
+{
+	struct bio *bio = NULL;
+	sector_t last_block_in_bio = 0;
+	const unsigned blkbits = inode->i_blkbits;
+	const unsigned blocksize = 1 << blkbits;
+	sector_t block_in_file;
+	sector_t last_block;
+	sector_t last_block_in_file;
+	sector_t first_block;
+	loff_t pos;
+	unsigned page_block;
+	struct block_device *bdev = inode->i_sb->s_bdev;
+	int length;
+	unsigned relative_block = 0;
+	struct ext4_map_blocks map;
+	unsigned int nr_pages, folio_pages;
+
+	map.m_pblk = 0;
+	map.m_lblk = 0;
+	map.m_len = 0;
+	map.m_flags = 0;
+
+	nr_pages = rac ? readahead_count(rac) : folio_nr_pages(folio);
+	for (; nr_pages; nr_pages -= folio_pages) {
+		int fully_mapped = 1;
+		unsigned int first_hole;
+		unsigned int blocks_per_folio;
+
+		if (rac)
+			folio = readahead_folio(rac);
+
+		folio_pages = folio_nr_pages(folio);
+		prefetchw(&folio->flags);
+
+		if (folio_buffers(folio))
+			goto confused;
+
+		blocks_per_folio = folio_size(folio) >> blkbits;
+		first_hole = blocks_per_folio;
+		pos = folio_pos(folio);
+		block_in_file = pos >> blkbits;
+		last_block = EXT4_PG_TO_LBLK(inode, folio->index + nr_pages);
+		last_block_in_file = (ext4_readpage_limit(inode) +
+				      blocksize - 1) >> blkbits;
+		if (last_block > last_block_in_file)
+			last_block = last_block_in_file;
+		page_block = 0;
+
+		/*
+		 * Map blocks using the previous result first.
+		 */
+		if ((map.m_flags & EXT4_MAP_MAPPED) &&
+		    block_in_file > map.m_lblk &&
+		    block_in_file < (map.m_lblk + map.m_len)) {
+			unsigned map_offset = block_in_file - map.m_lblk;
+			unsigned last = map.m_len - map_offset;
+
+			first_block = map.m_pblk + map_offset;
+			for (relative_block = 0; ; relative_block++) {
+				if (relative_block == last) {
+					/* needed? */
+					map.m_flags &= ~EXT4_MAP_MAPPED;
+					break;
+				}
+				if (page_block == blocks_per_folio)
+					break;
+				page_block++;
+				block_in_file++;
+			}
+		}
+
+		/*
+		 * Then do more ext4_map_blocks() calls until we are
+		 * done with this folio.
+		 */
+		while (page_block < blocks_per_folio) {
+			if (block_in_file < last_block) {
+				map.m_lblk = block_in_file;
+				map.m_len = last_block - block_in_file;
+
+				if (ext4_map_blocks(NULL, inode, &map, 0) < 0) {
+				set_error_page:
+					folio_zero_segment(folio, 0,
+							  folio_size(folio));
+					folio_unlock(folio);
+					goto next_page;
+				}
+			}
+			if ((map.m_flags & EXT4_MAP_MAPPED) == 0) {
+				fully_mapped = 0;
+				if (first_hole == blocks_per_folio)
+					first_hole = page_block;
+				page_block++;
+				block_in_file++;
+				continue;
+			}
+			if (first_hole != blocks_per_folio)
+				goto confused;		/* hole -> non-hole */
+
+			/* Contiguous blocks? */
+			if (!page_block)
+				first_block = map.m_pblk;
+			else if (first_block + page_block != map.m_pblk)
+				goto confused;
+			for (relative_block = 0; ; relative_block++) {
+				if (relative_block == map.m_len) {
+					/* needed? */
+					map.m_flags &= ~EXT4_MAP_MAPPED;
+					break;
+				} else if (page_block == blocks_per_folio)
+					break;
+				page_block++;
+				block_in_file++;
+			}
+		}
+		if (first_hole != blocks_per_folio) {
+			folio_zero_segment(folio, first_hole << blkbits,
+					  folio_size(folio));
+			if (first_hole == 0) {
+				if (vi && !fsverity_verify_folio(vi, folio))
+					goto set_error_page;
+				folio_end_read(folio, true);
+				continue;
+			}
+		} else if (fully_mapped) {
+			folio_set_mappedtodisk(folio);
+		}
+
+		/*
+		 * This folio will go to BIO.  Do we need to send this
+		 * BIO off first?
+		 */
+		if (bio && (last_block_in_bio != first_block - 1 ||
+			    !fscrypt_mergeable_bio(bio, inode, pos))) {
+		submit_and_realloc:
+			blk_crypto_submit_bio(bio);
+			bio = NULL;
+		}
+		if (bio == NULL) {
+			/*
+			 * bio_alloc will _always_ be able to allocate a bio if
+			 * __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset().
+			 */
+			bio = bio_alloc(bdev, bio_max_segs(nr_pages),
+					REQ_OP_READ, GFP_KERNEL);
+			fscrypt_set_bio_crypt_ctx(bio, inode, pos, GFP_KERNEL);
+			ext4_set_verity_work(bio, vi);
+			bio->bi_iter.bi_sector = first_block << (blkbits - 9);
+			bio->bi_end_io = mpage_end_io;
+			if (rac)
+				bio->bi_opf |= REQ_RAHEAD;
+		}
+
+		length = first_hole << blkbits;
+		if (!bio_add_folio(bio, folio, length, 0))
+			goto submit_and_realloc;
+
+		if (((map.m_flags & EXT4_MAP_BOUNDARY) &&
+		     (relative_block == map.m_len)) ||
+		    (first_hole != blocks_per_folio)) {
+			blk_crypto_submit_bio(bio);
+			bio = NULL;
+		} else
+			last_block_in_bio = first_block + blocks_per_folio - 1;
+		continue;
+	confused:
+		if (bio) {
+			blk_crypto_submit_bio(bio);
+			bio = NULL;
+		}
+		if (!folio_test_uptodate(folio))
+			block_read_full_folio(folio, ext4_get_block);
+		else
+			folio_unlock(folio);
+next_page:
+		; /* A label shall be followed by a statement until C23 */
+	}
+	if (bio)
+		blk_crypto_submit_bio(bio);
+	return 0;
+}
+
+int ext4_read_folio(struct file *file, struct folio *folio)
+{
+	struct inode *inode = folio->mapping->host;
+	struct fsverity_info *vi = NULL;
+	int ret;
+
+	trace_ext4_read_folio(inode, folio);
+
+	if (ext4_has_inline_data(inode)) {
+		ret = ext4_readpage_inline(inode, folio);
+		if (ret != -EAGAIN)
+			return ret;
+	}
+
+	if (folio->index < DIV_ROUND_UP(inode->i_size, PAGE_SIZE))
+		vi = fsverity_get_info(inode);
+	if (vi)
+		fsverity_readahead(vi, folio->index, folio_nr_pages(folio));
+	return ext4_mpage_readpages(inode, vi, NULL, folio);
+}
+
+void ext4_readahead(struct readahead_control *rac)
+{
+	struct inode *inode = rac->mapping->host;
+	struct fsverity_info *vi = NULL;
+
+	/* If the file has inline data, no need to do readahead. */
+	if (ext4_has_inline_data(inode))
+		return;
+
+	if (readahead_index(rac) < DIV_ROUND_UP(inode->i_size, PAGE_SIZE))
+		vi = fsverity_get_info(inode);
+	if (vi)
+		fsverity_readahead(vi, readahead_index(rac),
+				   readahead_count(rac));
+	ext4_mpage_readpages(inode, vi, rac, NULL);
+}
+
+int __init ext4_init_verity_caches(void)
+{
+	if (!IS_ENABLED(CONFIG_FS_VERITY))
+		return 0;
+	ext4_verity_work_cache =
+		KMEM_CACHE(ext4_verity_work, SLAB_RECLAIM_ACCOUNT);
+
+	if (!ext4_verity_work_cache)
+		goto fail;
+	ext4_verity_work_pool = mempool_create_slab_pool(
+		NUM_VERITY_WORKS, ext4_verity_work_cache);
+	if (!ext4_verity_work_pool)
+		goto fail_free_cache;
+	return 0;
+
+fail_free_cache:
+	kmem_cache_destroy(ext4_verity_work_cache);
+fail:
+	return -ENOMEM;
+}
+
+void ext4_exit_verity_caches(void)
+{
+	if (!IS_ENABLED(CONFIG_FS_VERITY))
+		return;
+	mempool_destroy(ext4_verity_work_pool);
+	kmem_cache_destroy(ext4_verity_work_cache);
+}