erofs: support compressed inodes for fileio

Use pseudo bios just like the previous fscache approach since
merged bio_vecs can be filled properly with unique interfaces.
Reviewed-by: Sandeep Dhavale <dhavale@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240830032840.3783206-3-hsiangkao@linux.alibaba.com

fs/erofs/fileio.c

@@ -23,7 +23,6 @@ static void erofs_fileio_ki_complete(struct kiocb *iocb, long ret)
 			container_of(iocb, struct erofs_fileio_rq, iocb);
 	struct folio_iter fi;
 
-	DBG_BUGON(rq->bio.bi_end_io);
 	if (ret > 0) {
 		if (ret != rq->bio.bi_iter.bi_size) {
 			bio_advance(&rq->bio, ret);
@@ -31,10 +30,14 @@ static void erofs_fileio_ki_complete(struct kiocb *iocb, long ret)
 		}
 		ret = 0;
 	}
+	if (rq->bio.bi_end_io) {
+		rq->bio.bi_end_io(&rq->bio);
+	} else {
 		bio_for_each_folio_all(fi, &rq->bio) {
 			DBG_BUGON(folio_test_uptodate(fi.folio));
 			erofs_onlinefolio_end(fi.folio, ret);
 		}
+	}
 	bio_uninit(&rq->bio);
 	kfree(rq);
 }
@@ -68,6 +71,17 @@ static struct erofs_fileio_rq *erofs_fileio_rq_alloc(struct erofs_map_dev *mdev)
 	return rq;
 }
 
+struct bio *erofs_fileio_bio_alloc(struct erofs_map_dev *mdev)
+{
+	return &erofs_fileio_rq_alloc(mdev)->bio;
+}
+
+void erofs_fileio_submit_bio(struct bio *bio)
+{
+	return erofs_fileio_rq_submit(container_of(bio, struct erofs_fileio_rq,
+						   bio));
+}
+
 static int erofs_fileio_scan_folio(struct erofs_fileio *io, struct folio *folio)
 {
 	struct inode *inode = folio_inode(folio);

fs/erofs/inode.c

@@ -252,12 +252,6 @@ static int erofs_fill_inode(struct inode *inode)
 	mapping_set_large_folios(inode->i_mapping);
 	if (erofs_inode_is_data_compressed(vi->datalayout)) {
 #ifdef CONFIG_EROFS_FS_ZIP
-#ifdef CONFIG_EROFS_FS_BACKED_BY_FILE
-		if (erofs_is_fileio_mode(EROFS_SB(inode->i_sb))) {
-			err = -EOPNOTSUPP;
-			goto out_unlock;
-		}
-#endif
 		DO_ONCE_LITE_IF(inode->i_blkbits != PAGE_SHIFT,
 			  erofs_info, inode->i_sb,
 			  "EXPERIMENTAL EROFS subpage compressed block support in use. Use at your own risk!");

fs/erofs/internal.h

@@ -489,6 +489,14 @@ static inline void z_erofs_exit_subsystem(void) {}
 static inline int erofs_init_managed_cache(struct super_block *sb) { return 0; }
 #endif	/* !CONFIG_EROFS_FS_ZIP */
 
+#ifdef CONFIG_EROFS_FS_BACKED_BY_FILE
+struct bio *erofs_fileio_bio_alloc(struct erofs_map_dev *mdev);
+void erofs_fileio_submit_bio(struct bio *bio);
+#else
+static inline struct bio *erofs_fileio_bio_alloc(struct erofs_map_dev *mdev) { return NULL; }
+static inline void erofs_fileio_submit_bio(struct bio *bio) {}
+#endif
+
 #ifdef CONFIG_EROFS_FS_ONDEMAND
 int erofs_fscache_register_fs(struct super_block *sb);
 void erofs_fscache_unregister_fs(struct super_block *sb);

fs/erofs/zdata.c

@@ -1618,10 +1618,12 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
 			if (bio && (cur != last_pa ||
 				    bio->bi_bdev != mdev.m_bdev)) {
 drain_io:
-				if (!erofs_is_fscache_mode(sb))
-					submit_bio(bio);
-				else
+				if (erofs_is_fileio_mode(EROFS_SB(sb)))
+					erofs_fileio_submit_bio(bio);
+				else if (erofs_is_fscache_mode(sb))
 					erofs_fscache_submit_bio(bio);
+				else
+					submit_bio(bio);
 
 				if (memstall) {
 					psi_memstall_leave(&pflags);
@@ -1646,9 +1648,12 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
 			}
 
 			if (!bio) {
-				bio = erofs_is_fscache_mode(sb) ?
-					erofs_fscache_bio_alloc(&mdev) :
-					bio_alloc(mdev.m_bdev, BIO_MAX_VECS,
+				if (erofs_is_fileio_mode(EROFS_SB(sb)))
+					bio = erofs_fileio_bio_alloc(&mdev);
+				else if (erofs_is_fscache_mode(sb))
+					bio = erofs_fscache_bio_alloc(&mdev);
+				else
+					bio = bio_alloc(mdev.m_bdev, BIO_MAX_VECS,
 							REQ_OP_READ, GFP_NOIO);
 				bio->bi_end_io = z_erofs_endio;
 				bio->bi_iter.bi_sector = cur >> 9;
@@ -1672,10 +1677,12 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
 	} while (owned_head != Z_EROFS_PCLUSTER_TAIL);
 
 	if (bio) {
-		if (!erofs_is_fscache_mode(sb))
-			submit_bio(bio);
-		else
+		if (erofs_is_fileio_mode(EROFS_SB(sb)))
+			erofs_fileio_submit_bio(bio);
+		else if (erofs_is_fscache_mode(sb))
 			erofs_fscache_submit_bio(bio);
+		else
+			submit_bio(bio);
 		if (memstall)
 			psi_memstall_leave(&pflags);
 	}