1 files changed, 404 insertions, 277 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 6c7eb80220ca..32da97c3c19d 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -29,6 +29,7 @@
 #include "compression.h"
 #include "extent_io.h"
 #include "extent_map.h"
+#include "subpage.h"
 #include "zoned.h"
 
 static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" };
@@ -181,9 +182,9 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
 			if (memcmp(&csum, cb_sum, csum_size) != 0) {
 				btrfs_print_data_csum_error(inode, disk_start,
 						csum, cb_sum, cb->mirror_num);
-				if (btrfs_io_bio(bio)->device)
+				if (btrfs_bio(bio)->device)
 					btrfs_dev_stat_inc_and_print(
-						btrfs_io_bio(bio)->device,
+						btrfs_bio(bio)->device,
 						BTRFS_DEV_STAT_CORRUPTION_ERRS);
 				return -EIO;
 			}
@@ -194,6 +195,87 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
 	return 0;
 }
 
+/*
+ * Reduce bio and io accounting for a compressed_bio with its corresponding bio.
+ *
+ * Return true if there is no pending bio nor io.
+ * Return false otherwise.
+ */
+static bool dec_and_test_compressed_bio(struct compressed_bio *cb, struct bio *bio)
+{
+	struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
+	unsigned int bi_size = 0;
+	bool last_io = false;
+	struct bio_vec *bvec;
+	struct bvec_iter_all iter_all;
+
+	/*
+	 * At endio time, bi_iter.bi_size doesn't represent the real bio size.
+	 * Thus here we have to iterate through all segments to grab correct
+	 * bio size.
+	 */
+	bio_for_each_segment_all(bvec, bio, iter_all)
+		bi_size += bvec->bv_len;
+
+	if (bio->bi_status)
+		cb->errors = 1;
+
+	ASSERT(bi_size && bi_size <= cb->compressed_len);
+	last_io = refcount_sub_and_test(bi_size >> fs_info->sectorsize_bits,
+					&cb->pending_sectors);
+	/*
+	 * Here we must wake up the possible error handler after all other
+	 * operations on @cb finished, or we can race with
+	 * finish_compressed_bio_*() which may free @cb.
+	 */
+	wake_up_var(cb);
+
+	return last_io;
+}
+
+static void finish_compressed_bio_read(struct compressed_bio *cb, struct bio *bio)
+{
+	unsigned int index;
+	struct page *page;
+
+	/* Release the compressed pages */
+	for (index = 0; index < cb->nr_pages; index++) {
+		page = cb->compressed_pages[index];
+		page->mapping = NULL;
+		put_page(page);
+	}
+
+	/* Do io completion on the original bio */
+	if (cb->errors) {
+		bio_io_error(cb->orig_bio);
+	} else {
+		struct bio_vec *bvec;
+		struct bvec_iter_all iter_all;
+
+		ASSERT(bio);
+		ASSERT(!bio->bi_status);
+		/*
+		 * We have verified the checksum already, set page checked so
+		 * the end_io handlers know about it
+		 */
+		ASSERT(!bio_flagged(bio, BIO_CLONED));
+		bio_for_each_segment_all(bvec, cb->orig_bio, iter_all) {
+			u64 bvec_start = page_offset(bvec->bv_page) +
+					 bvec->bv_offset;
+
+			btrfs_page_set_checked(btrfs_sb(cb->inode->i_sb),
+					bvec->bv_page, bvec_start,
+					bvec->bv_len);
+		}
+
+		bio_endio(cb->orig_bio);
+	}
+
+	/* Finally free the cb struct */
+	kfree(cb->compressed_pages);
+	kfree(cb);
+}
+
 /* when we finish reading compressed pages from the disk, we
  * decompress them and then run the bio end_io routines on the
  * decompressed pages (in the inode address space).
@@ -208,25 +290,17 @@ static void end_compressed_bio_read(struct bio *bio)
 {
 	struct compressed_bio *cb = bio->bi_private;
 	struct inode *inode;
-	struct page *page;
-	unsigned int index;
-	unsigned int mirror = btrfs_io_bio(bio)->mirror_num;
+	unsigned int mirror = btrfs_bio(bio)->mirror_num;
 	int ret = 0;
 
-	if (bio->bi_status)
-		cb->errors = 1;
-
-	/* if there are more bios still pending for this compressed
-	 * extent, just exit
-	 */
-	if (!refcount_dec_and_test(&cb->pending_bios))
+	if (!dec_and_test_compressed_bio(cb, bio))
 		goto out;
 
 	/*
 	 * Record the correct mirror_num in cb->orig_bio so that
 	 * read-repair can work properly.
 	 */
-	btrfs_io_bio(cb->orig_bio)->mirror_num = mirror;
+	btrfs_bio(cb->orig_bio)->mirror_num = mirror;
 	cb->mirror_num = mirror;
 
 	/*
@@ -250,36 +324,7 @@ static void end_compressed_bio_read(struct bio *bio)
 csum_failed:
 	if (ret)
 		cb->errors = 1;
-
-	/* release the compressed pages */
-	index = 0;
-	for (index = 0; index < cb->nr_pages; index++) {
-		page = cb->compressed_pages[index];
-		page->mapping = NULL;
-		put_page(page);
-	}
-
-	/* do io completion on the original bio */
-	if (cb->errors) {
-		bio_io_error(cb->orig_bio);
-	} else {
-		struct bio_vec *bvec;
-		struct bvec_iter_all iter_all;
-
-		/*
-		 * we have verified the checksum already, set page
-		 * checked so the end_io handlers know about it
-		 */
-		ASSERT(!bio_flagged(bio, BIO_CLONED));
-		bio_for_each_segment_all(bvec, cb->orig_bio, iter_all)
-			SetPageChecked(bvec->bv_page);
-
-		bio_endio(cb->orig_bio);
-	}
-
-	/* finally free the cb struct */
-	kfree(cb->compressed_pages);
-	kfree(cb);
+	finish_compressed_bio_read(cb, bio);
 out:
 	bio_put(bio);
 }
@@ -291,6 +336,7 @@ out:
 static noinline void end_compressed_writeback(struct inode *inode,
 					      const struct compressed_bio *cb)
 {
+	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	unsigned long index = cb->start >> PAGE_SHIFT;
 	unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
 	struct page *pages[16];
@@ -313,7 +359,8 @@ static noinline void end_compressed_writeback(struct inode *inode,
 		for (i = 0; i < ret; i++) {
 			if (cb->errors)
 				SetPageError(pages[i]);
-			end_page_writeback(pages[i]);
+			btrfs_page_clamp_clear_writeback(fs_info, pages[i],
+							 cb->start, cb->len);
 			put_page(pages[i]);
 		}
 		nr_pages -= ret;
@@ -322,60 +369,127 @@ static noinline void end_compressed_writeback(struct inode *inode,
 	/* the inode may be gone now */
 }
 
-/*
- * do the cleanup once all the compressed pages hit the disk.
- * This will clear writeback on the file pages and free the compressed
- * pages.
- *
- * This also calls the writeback end hooks for the file pages so that
- * metadata and checksums can be updated in the file.
- */
-static void end_compressed_bio_write(struct bio *bio)
+static void finish_compressed_bio_write(struct compressed_bio *cb)
 {
-	struct compressed_bio *cb = bio->bi_private;
-	struct inode *inode;
-	struct page *page;
+	struct inode *inode = cb->inode;
 	unsigned int index;
 
-	if (bio->bi_status)
-		cb->errors = 1;
-
-	/* if there are more bios still pending for this compressed
-	 * extent, just exit
-	 */
-	if (!refcount_dec_and_test(&cb->pending_bios))
-		goto out;
-
-	/* ok, we're the last bio for this extent, step one is to
-	 * call back into the FS and do all the end_io operations
+	/*
+	 * Ok, we're the last bio for this extent, step one is to call back
+	 * into the FS and do all the end_io operations.
 	 */
-	inode = cb->inode;
-	btrfs_record_physical_zoned(inode, cb->start, bio);
 	btrfs_writepage_endio_finish_ordered(BTRFS_I(inode), NULL,
 			cb->start, cb->start + cb->len - 1,
 			!cb->errors);
 
 	end_compressed_writeback(inode, cb);
-	/* note, our inode could be gone now */
+	/* Note, our inode could be gone now */
 
 	/*
-	 * release the compressed pages, these came from alloc_page and
+	 * Release the compressed pages, these came from alloc_page and
 	 * are not attached to the inode at all
 	 */
-	index = 0;
 	for (index = 0; index < cb->nr_pages; index++) {
-		page = cb->compressed_pages[index];
+		struct page *page = cb->compressed_pages[index];
+
 		page->mapping = NULL;
 		put_page(page);
 	}
 
-	/* finally free the cb struct */
+	/* Finally free the cb struct */
 	kfree(cb->compressed_pages);
 	kfree(cb);
+}
+
+/*
+ * Do the cleanup once all the compressed pages hit the disk.  This will clear
+ * writeback on the file pages and free the compressed pages.
+ *
+ * This also calls the writeback end hooks for the file pages so that metadata
+ * and checksums can be updated in the file.
+ */
+static void end_compressed_bio_write(struct bio *bio)
+{
+	struct compressed_bio *cb = bio->bi_private;
+
+	if (!dec_and_test_compressed_bio(cb, bio))
+		goto out;
+
+	btrfs_record_physical_zoned(cb->inode, cb->start, bio);
+
+	finish_compressed_bio_write(cb);
 out:
 	bio_put(bio);
 }
 
+static blk_status_t submit_compressed_bio(struct btrfs_fs_info *fs_info,
+					  struct compressed_bio *cb,
+					  struct bio *bio, int mirror_num)
+{
+	blk_status_t ret;
+
+	ASSERT(bio->bi_iter.bi_size);
+	ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
+	if (ret)
+		return ret;
+	ret = btrfs_map_bio(fs_info, bio, mirror_num);
+	return ret;
+}
+
+/*
+ * Allocate a compressed_bio, which will be used to read/write on-disk
+ * (aka, compressed) * data.
+ *
+ * @cb:                 The compressed_bio structure, which records all the needed
+ *                      information to bind the compressed data to the uncompressed
+ *                      page cache.
+ * @disk_byten:         The logical bytenr where the compressed data will be read
+ *                      from or written to.
+ * @endio_func:         The endio function to call after the IO for compressed data
+ *                      is finished.
+ * @next_stripe_start:  Return value of logical bytenr of where next stripe starts.
+ *                      Let the caller know to only fill the bio up to the stripe
+ *                      boundary.
+ */
+
+
+static struct bio *alloc_compressed_bio(struct compressed_bio *cb, u64 disk_bytenr,
+					unsigned int opf, bio_end_io_t endio_func,
+					u64 *next_stripe_start)
+{
+	struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
+	struct btrfs_io_geometry geom;
+	struct extent_map *em;
+	struct bio *bio;
+	int ret;
+
+	bio = btrfs_bio_alloc(BIO_MAX_VECS);
+
+	bio->bi_iter.bi_sector = disk_bytenr >> SECTOR_SHIFT;
+	bio->bi_opf = opf;
+	bio->bi_private = cb;
+	bio->bi_end_io = endio_func;
+
+	em = btrfs_get_chunk_map(fs_info, disk_bytenr, fs_info->sectorsize);
+	if (IS_ERR(em)) {
+		bio_put(bio);
+		return ERR_CAST(em);
+	}
+
+	if (bio_op(bio) == REQ_OP_ZONE_APPEND)
+		bio_set_dev(bio, em->map_lookup->stripes[0].dev->bdev);
+
+	ret = btrfs_get_io_geometry(fs_info, em, btrfs_op(bio), disk_bytenr, &geom);
+	free_extent_map(em);
+	if (ret < 0) {
+		bio_put(bio);
+		return ERR_PTR(ret);
+	}
+	*next_stripe_start = disk_bytenr + geom.len;
+
+	return bio;
+}
+
 /*
  * worker function to build and submit bios for previously compressed pages.
  * The corresponding pages in the inode should be marked for writeback
@@ -396,20 +510,19 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	struct bio *bio = NULL;
 	struct compressed_bio *cb;
-	unsigned long bytes_left;
-	int pg_index = 0;
-	struct page *page;
-	u64 first_byte = disk_start;
+	u64 cur_disk_bytenr = disk_start;
+	u64 next_stripe_start;
 	blk_status_t ret;
 	int skip_sum = inode->flags & BTRFS_INODE_NODATASUM;
 	const bool use_append = btrfs_use_zone_append(inode, disk_start);
 	const unsigned int bio_op = use_append ? REQ_OP_ZONE_APPEND : REQ_OP_WRITE;
 
-	WARN_ON(!PAGE_ALIGNED(start));
+	ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
+	       IS_ALIGNED(len, fs_info->sectorsize));
 	cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
 	if (!cb)
 		return BLK_STS_RESOURCE;
-	refcount_set(&cb->pending_bios, 0);
+	refcount_set(&cb->pending_sectors, compressed_len >> fs_info->sectorsize_bits);
 	cb->errors = 0;
 	cb->inode = &inode->vfs_inode;
 	cb->start = start;
@@ -420,118 +533,100 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 	cb->orig_bio = NULL;
 	cb->nr_pages = nr_pages;
 
-	bio = btrfs_bio_alloc(first_byte);
-	bio->bi_opf = bio_op | write_flags;
-	bio->bi_private = cb;
-	bio->bi_end_io = end_compressed_bio_write;
-
-	if (use_append) {
-		struct btrfs_device *device;
-
-		device = btrfs_zoned_get_device(fs_info, disk_start, PAGE_SIZE);
-		if (IS_ERR(device)) {
-			kfree(cb);
-			bio_put(bio);
-			return BLK_STS_NOTSUPP;
+	while (cur_disk_bytenr < disk_start + compressed_len) {
+		u64 offset = cur_disk_bytenr - disk_start;
+		unsigned int index = offset >> PAGE_SHIFT;
+		unsigned int real_size;
+		unsigned int added;
+		struct page *page = compressed_pages[index];
+		bool submit = false;
+
+		/* Allocate new bio if submitted or not yet allocated */
+		if (!bio) {
+			bio = alloc_compressed_bio(cb, cur_disk_bytenr,
+				bio_op | write_flags, end_compressed_bio_write,
+				&next_stripe_start);
+			if (IS_ERR(bio)) {
+				ret = errno_to_blk_status(PTR_ERR(bio));
+				bio = NULL;
+				goto finish_cb;
+			}
 		}
-
-		bio_set_dev(bio, device->bdev);
-	}
-
-	if (blkcg_css) {
-		bio->bi_opf |= REQ_CGROUP_PUNT;
-		kthread_associate_blkcg(blkcg_css);
-	}
-	refcount_set(&cb->pending_bios, 1);
-
-	/* create and submit bios for the compressed pages */
-	bytes_left = compressed_len;
-	for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
-		int submit = 0;
-		int len = 0;
-
-		page = compressed_pages[pg_index];
-		page->mapping = inode->vfs_inode.i_mapping;
-		if (bio->bi_iter.bi_size)
-			submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio,
-							  0);
-
 		/*
-		 * Page can only be added to bio if the current bio fits in
-		 * stripe.
+		 * We should never reach next_stripe_start start as we will
+		 * submit comp_bio when reach the boundary immediately.
 		 */
-		if (!submit) {
-			if (pg_index == 0 && use_append)
-				len = bio_add_zone_append_page(bio, page,
-							       PAGE_SIZE, 0);
-			else
-				len = bio_add_page(bio, page, PAGE_SIZE, 0);
-		}
-
-		page->mapping = NULL;
-		if (submit || len < PAGE_SIZE) {
-			/*
-			 * inc the count before we submit the bio so
-			 * we know the end IO handler won't happen before
-			 * we inc the count.  Otherwise, the cb might get
-			 * freed before we're done setting it up
-			 */
-			refcount_inc(&cb->pending_bios);
-			ret = btrfs_bio_wq_end_io(fs_info, bio,
-						  BTRFS_WQ_ENDIO_DATA);
-			BUG_ON(ret); /* -ENOMEM */
+		ASSERT(cur_disk_bytenr != next_stripe_start);
 
+		/*
+		 * We have various limits on the real read size:
+		 * - stripe boundary
+		 * - page boundary
+		 * - compressed length boundary
+		 */
+		real_size = min_t(u64, U32_MAX, next_stripe_start - cur_disk_bytenr);
+		real_size = min_t(u64, real_size, PAGE_SIZE - offset_in_page(offset));
+		real_size = min_t(u64, real_size, compressed_len - offset);
+		ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
+
+		if (use_append)
+			added = bio_add_zone_append_page(bio, page, real_size,
+					offset_in_page(offset));
+		else
+			added = bio_add_page(bio, page, real_size,
+					offset_in_page(offset));
+		/* Reached zoned boundary */
+		if (added == 0)
+			submit = true;
+
+		cur_disk_bytenr += added;
+		/* Reached stripe boundary */
+		if (cur_disk_bytenr == next_stripe_start)
+			submit = true;
+
+		/* Finished the range */
+		if (cur_disk_bytenr == disk_start + compressed_len)
+			submit = true;
+
+		if (submit) {
 			if (!skip_sum) {
 				ret = btrfs_csum_one_bio(inode, bio, start, 1);
-				BUG_ON(ret); /* -ENOMEM */
-			}
-
-			ret = btrfs_map_bio(fs_info, bio, 0);
-			if (ret) {
-				bio->bi_status = ret;
-				bio_endio(bio);
+				if (ret)
+					goto finish_cb;
 			}
 
-			bio = btrfs_bio_alloc(first_byte);
-			bio->bi_opf = bio_op | write_flags;
-			bio->bi_private = cb;
-			bio->bi_end_io = end_compressed_bio_write;
-			if (blkcg_css)
-				bio->bi_opf |= REQ_CGROUP_PUNT;
-			/*
-			 * Use bio_add_page() to ensure the bio has at least one
-			 * page.
-			 */
-			bio_add_page(bio, page, PAGE_SIZE, 0);
+			ret = submit_compressed_bio(fs_info, cb, bio, 0);
+			if (ret)
+				goto finish_cb;
+			bio = NULL;
 		}
-		if (bytes_left < PAGE_SIZE) {
-			btrfs_info(fs_info,
-					"bytes left %lu compress len %u nr %u",
-			       bytes_left, cb->compressed_len, cb->nr_pages);
-		}
-		bytes_left -= PAGE_SIZE;
-		first_byte += PAGE_SIZE;
 		cond_resched();
 	}
+	if (blkcg_css)
+		kthread_associate_blkcg(NULL);
 
-	ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
-	BUG_ON(ret); /* -ENOMEM */
-
-	if (!skip_sum) {
-		ret = btrfs_csum_one_bio(inode, bio, start, 1);
-		BUG_ON(ret); /* -ENOMEM */
-	}
+	return 0;
 
-	ret = btrfs_map_bio(fs_info, bio, 0);
-	if (ret) {
+finish_cb:
+	if (bio) {
 		bio->bi_status = ret;
 		bio_endio(bio);
 	}
+	/* Last byte of @cb is submitted, endio will free @cb */
+	if (cur_disk_bytenr == disk_start + compressed_len)
+		return ret;
 
-	if (blkcg_css)
-		kthread_associate_blkcg(NULL);
-
-	return 0;
+	wait_var_event(cb, refcount_read(&cb->pending_sectors) ==
+			   (disk_start + compressed_len - cur_disk_bytenr) >>
+			   fs_info->sectorsize_bits);
+	/*
+	 * Even with previous bio ended, we should still have io not yet
+	 * submitted, thus need to finish manually.
+	 */
+	ASSERT(refcount_read(&cb->pending_sectors));
+	/* Now we are the only one referring @cb, can finish it safely. */
+	finish_compressed_bio_write(cb);
+	return ret;
 }
 
 static u64 bio_end_offset(struct bio *bio)
@@ -541,25 +636,33 @@ static u64 bio_end_offset(struct bio *bio)
 	return page_offset(last->bv_page) + last->bv_len + last->bv_offset;
 }
 
+/*
+ * Add extra pages in the same compressed file extent so that we don't need to
+ * re-read the same extent again and again.
+ *
+ * NOTE: this won't work well for subpage, as for subpage read, we lock the
+ * full page then submit bio for each compressed/regular extents.
+ *
+ * This means, if we have several sectors in the same page points to the same
+ * on-disk compressed data, we will re-read the same extent many times and
+ * this function can only help for the next page.
+ */
 static noinline int add_ra_bio_pages(struct inode *inode,
 				     u64 compressed_end,
 				     struct compressed_bio *cb)
 {
+	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	unsigned long end_index;
-	unsigned long pg_index;
-	u64 last_offset;
+	u64 cur = bio_end_offset(cb->orig_bio);
 	u64 isize = i_size_read(inode);
 	int ret;
 	struct page *page;
-	unsigned long nr_pages = 0;
 	struct extent_map *em;
 	struct address_space *mapping = inode->i_mapping;
 	struct extent_map_tree *em_tree;
 	struct extent_io_tree *tree;
-	u64 end;
-	int misses = 0;
+	int sectors_missed = 0;
 
-	last_offset = bio_end_offset(cb->orig_bio);
 	em_tree = &BTRFS_I(inode)->extent_tree;
 	tree = &BTRFS_I(inode)->io_tree;
 
@@ -578,18 +681,29 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 
 	end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
 
-	while (last_offset < compressed_end) {
-		pg_index = last_offset >> PAGE_SHIFT;
+	while (cur < compressed_end) {
+		u64 page_end;
+		u64 pg_index = cur >> PAGE_SHIFT;
+		u32 add_size;
 
 		if (pg_index > end_index)
 			break;
 
 		page = xa_load(&mapping->i_pages, pg_index);
 		if (page && !xa_is_value(page)) {
-			misses++;
-			if (misses > 4)
+			sectors_missed += (PAGE_SIZE - offset_in_page(cur)) >>
+					  fs_info->sectorsize_bits;
+
+			/* Beyond threshold, no need to continue */
+			if (sectors_missed > 4)
 				break;
-			goto next;
+
+			/*
+			 * Jump to next page start as we already have page for
+			 * current offset.
+			 */
+			cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE;
+			continue;
 		}
 
 		page = __page_cache_alloc(mapping_gfp_constraint(mapping,
@@ -599,14 +713,11 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 
 		if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
 			put_page(page);
-			goto next;
+			/* There is already a page, skip to page end */
+			cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE;
+			continue;
 		}
 
-		/*
-		 * at this point, we have a locked page in the page cache
-		 * for these bytes in the file.  But, we have to make
-		 * sure they map to this compressed extent on disk.
-		 */
 		ret = set_page_extent_mapped(page);
 		if (ret < 0) {
 			unlock_page(page);
@@ -614,18 +725,22 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 			break;
 		}
 
-		end = last_offset + PAGE_SIZE - 1;
-		lock_extent(tree, last_offset, end);
+		page_end = (pg_index << PAGE_SHIFT) + PAGE_SIZE - 1;
+		lock_extent(tree, cur, page_end);
 		read_lock(&em_tree->lock);
-		em = lookup_extent_mapping(em_tree, last_offset,
-					   PAGE_SIZE);
+		em = lookup_extent_mapping(em_tree, cur, page_end + 1 - cur);
 		read_unlock(&em_tree->lock);
 
-		if (!em || last_offset < em->start ||
-		    (last_offset + PAGE_SIZE > extent_map_end(em)) ||
+		/*
+		 * At this point, we have a locked page in the page cache for
+		 * these bytes in the file.  But, we have to make sure they map
+		 * to this compressed extent on disk.
+		 */
+		if (!em || cur < em->start ||
+		    (cur + fs_info->sectorsize > extent_map_end(em)) ||
 		    (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
 			free_extent_map(em);
-			unlock_extent(tree, last_offset, end);
+			unlock_extent(tree, cur, page_end);
 			unlock_page(page);
 			put_page(page);
 			break;
@@ -643,20 +758,23 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 			}
 		}
 
-		ret = bio_add_page(cb->orig_bio, page,
-				   PAGE_SIZE, 0);
-
-		if (ret == PAGE_SIZE) {
-			nr_pages++;
-			put_page(page);
-		} else {
-			unlock_extent(tree, last_offset, end);
+		add_size = min(em->start + em->len, page_end + 1) - cur;
+		ret = bio_add_page(cb->orig_bio, page, add_size, offset_in_page(cur));
+		if (ret != add_size) {
+			unlock_extent(tree, cur, page_end);
 			unlock_page(page);
 			put_page(page);
 			break;
 		}
-next:
-		last_offset += PAGE_SIZE;
+		/*
+		 * If it's subpage, we also need to increase its
+		 * subpage::readers number, as at endio we will decrease
+		 * subpage::readers and to unlock the page.
+		 */
+		if (fs_info->sectorsize < PAGE_SIZE)
+			btrfs_subpage_start_reader(fs_info, page, cur, add_size);
+		put_page(page);
+		cur += add_size;
 	}
 	return 0;
 }
@@ -681,9 +799,10 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	unsigned int compressed_len;
 	unsigned int nr_pages;
 	unsigned int pg_index;
-	struct page *page;
-	struct bio *comp_bio;
-	u64 cur_disk_byte = bio->bi_iter.bi_sector << 9;
+	struct bio *comp_bio = NULL;
+	const u64 disk_bytenr = bio->bi_iter.bi_sector << SECTOR_SHIFT;
+	u64 cur_disk_byte = disk_bytenr;
+	u64 next_stripe_start;
 	u64 file_offset;
 	u64 em_len;
 	u64 em_start;
@@ -710,7 +829,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	if (!cb)
 		goto out;
 
-	refcount_set(&cb->pending_bios, 0);
+	refcount_set(&cb->pending_sectors, compressed_len >> fs_info->sectorsize_bits);
 	cb->errors = 0;
 	cb->inode = inode;
 	cb->mirror_num = mirror_num;
@@ -750,86 +869,74 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	/* include any pages we added in add_ra-bio_pages */
 	cb->len = bio->bi_iter.bi_size;
 
-	comp_bio = btrfs_bio_alloc(cur_disk_byte);
-	comp_bio->bi_opf = REQ_OP_READ;
-	comp_bio->bi_private = cb;
-	comp_bio->bi_end_io = end_compressed_bio_read;
-	refcount_set(&cb->pending_bios, 1);
-
-	for (pg_index = 0; pg_index < nr_pages; pg_index++) {
-		u32 pg_len = PAGE_SIZE;
-		int submit = 0;
+	while (cur_disk_byte < disk_bytenr + compressed_len) {
+		u64 offset = cur_disk_byte - disk_bytenr;
+		unsigned int index = offset >> PAGE_SHIFT;
+		unsigned int real_size;
+		unsigned int added;
+		struct page *page = cb->compressed_pages[index];
+		bool submit = false;
+
+		/* Allocate new bio if submitted or not yet allocated */
+		if (!comp_bio) {
+			comp_bio = alloc_compressed_bio(cb, cur_disk_byte,
+					REQ_OP_READ, end_compressed_bio_read,
+					&next_stripe_start);
+			if (IS_ERR(comp_bio)) {
+				ret = errno_to_blk_status(PTR_ERR(comp_bio));
+				comp_bio = NULL;
+				goto finish_cb;
+			}
+		}
+		/*
+		 * We should never reach next_stripe_start start as we will
+		 * submit comp_bio when reach the boundary immediately.
+		 */
+		ASSERT(cur_disk_byte != next_stripe_start);
+		/*
+		 * We have various limit on the real read size:
+		 * - stripe boundary
+		 * - page boundary
+		 * - compressed length boundary
+		 */
+		real_size = min_t(u64, U32_MAX, next_stripe_start - cur_disk_byte);
+		real_size = min_t(u64, real_size, PAGE_SIZE - offset_in_page(offset));
+		real_size = min_t(u64, real_size, compressed_len - offset);
+		ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
 
+		added = bio_add_page(comp_bio, page, real_size, offset_in_page(offset));
 		/*
-		 * To handle subpage case, we need to make sure the bio only
-		 * covers the range we need.
-		 *
-		 * If we're at the last page, truncate the length to only cover
-		 * the remaining part.
+		 * Maximum compressed extent is smaller than bio size limit,
+		 * thus bio_add_page() should always success.
 		 */
-		if (pg_index == nr_pages - 1)
-			pg_len = min_t(u32, PAGE_SIZE,
-					compressed_len - pg_index * PAGE_SIZE);
+		ASSERT(added == real_size);
+		cur_disk_byte += added;
 
-		page = cb->compressed_pages[pg_index];
-		page->mapping = inode->i_mapping;
-		page->index = em_start >> PAGE_SHIFT;
+		/* Reached stripe boundary, need to submit */
+		if (cur_disk_byte == next_stripe_start)
+			submit = true;
 
-		if (comp_bio->bi_iter.bi_size)
-			submit = btrfs_bio_fits_in_stripe(page, pg_len,
-							  comp_bio, 0);
+		/* Has finished the range, need to submit */
+		if (cur_disk_byte == disk_bytenr + compressed_len)
+			submit = true;
 
-		page->mapping = NULL;
-		if (submit || bio_add_page(comp_bio, page, pg_len, 0) < pg_len) {
+		if (submit) {
 			unsigned int nr_sectors;
 
-			ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
-						  BTRFS_WQ_ENDIO_DATA);
-			BUG_ON(ret); /* -ENOMEM */
-
-			/*
-			 * inc the count before we submit the bio so
-			 * we know the end IO handler won't happen before
-			 * we inc the count.  Otherwise, the cb might get
-			 * freed before we're done setting it up
-			 */
-			refcount_inc(&cb->pending_bios);
-
 			ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
-			BUG_ON(ret); /* -ENOMEM */
+			if (ret)
+				goto finish_cb;
 
 			nr_sectors = DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
 						  fs_info->sectorsize);
 			sums += fs_info->csum_size * nr_sectors;
 
-			ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
-			if (ret) {
-				comp_bio->bi_status = ret;
-				bio_endio(comp_bio);
-			}
-
-			comp_bio = btrfs_bio_alloc(cur_disk_byte);
-			comp_bio->bi_opf = REQ_OP_READ;
-			comp_bio->bi_private = cb;
-			comp_bio->bi_end_io = end_compressed_bio_read;
-
-			bio_add_page(comp_bio, page, pg_len, 0);
+			ret = submit_compressed_bio(fs_info, cb, comp_bio, mirror_num);
+			if (ret)
+				goto finish_cb;
+			comp_bio = NULL;
 		}
-		cur_disk_byte += pg_len;
 	}
-
-	ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
-	BUG_ON(ret); /* -ENOMEM */
-
-	ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
-	BUG_ON(ret); /* -ENOMEM */
-
-	ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
-	if (ret) {
-		comp_bio->bi_status = ret;
-		bio_endio(comp_bio);
-	}
-
 	return 0;
 
 fail2:
@@ -844,6 +951,26 @@ fail1:
 out:
 	free_extent_map(em);
 	return ret;
+finish_cb:
+	if (comp_bio) {
+		comp_bio->bi_status = ret;
+		bio_endio(comp_bio);
+	}
+	/* All bytes of @cb is submitted, endio will free @cb */
+	if (cur_disk_byte == disk_bytenr + compressed_len)
+		return ret;
+
+	wait_var_event(cb, refcount_read(&cb->pending_sectors) ==
+			   (disk_bytenr + compressed_len - cur_disk_byte) >>
+			   fs_info->sectorsize_bits);
+	/*
+	 * Even with previous bio ended, we should still have io not yet
+	 * submitted, thus need to finish @cb manually.
+	 */
+	ASSERT(refcount_read(&cb->pending_sectors));
+	/* Now we are the only one referring @cb, can finish it safely. */
+	finish_compressed_bio_read(cb, NULL);
+	return ret;
 }
 
 /*