Changes since last update:

- Fix wrong iomap->length calculation post EOF, which could
    cause a WARN_ON in iomap_iter_done() (Siddh);
 
  - Fix improper kvcalloc() use with __GFP_NOFAIL (me);
 
  - Add missing `domain_id` mount option in documentation (Jingbo);
 
  - Clean up fscache option parsing (Jingbo).
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Merge tag 'erofs-for-6.2-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs

Pull erofs fixes from Gao Xiang:
 "Two patches fixes issues reported by syzbot, one fixes a missing
  `domain_id` mount option in documentation and a minor cleanup:

   - Fix wrong iomap->length calculation post EOF, which could cause a
     WARN_ON in iomap_iter_done() (Siddh)

   - Fix improper kvcalloc() use with __GFP_NOFAIL (me)

   - Add missing `domain_id` mount option in documentation (Jingbo)

   - Clean up fscache option parsing (Jingbo)"

* tag 'erofs-for-6.2-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  erofs: clean up parsing of fscache related options
  erofs: add documentation for 'domain_id' mount option
  erofs: fix kvcalloc() misuse with __GFP_NOFAIL
  erofs/zmap.c: Fix incorrect offset calculation

Documentation/filesystems/erofs.rst

@@ -120,6 +120,8 @@ dax={always,never}     Use direct access (no page cache).  See
 dax                    A legacy option which is an alias for ``dax=always``.
 device=%s              Specify a path to an extra device to be used together.
 fsid=%s                Specify a filesystem image ID for Fscache back-end.
+domain_id=%s           Specify a domain ID in fscache mode so that different images
+                       with the same blobs under a given domain ID can share storage.
 ===================    =========================================================
 
 Sysfs Entries

fs/erofs/super.c

@@ -577,26 +577,25 @@ static int erofs_fc_parse_param(struct fs_context *fc,
 		}
 		++ctx->devs->extra_devices;
 		break;
-	case Opt_fsid:
 #ifdef CONFIG_EROFS_FS_ONDEMAND
+	case Opt_fsid:
 		kfree(ctx->fsid);
 		ctx->fsid = kstrdup(param->string, GFP_KERNEL);
 		if (!ctx->fsid)
 			return -ENOMEM;
-#else
-		errorfc(fc, "fsid option not supported");
-#endif
 		break;
 	case Opt_domain_id:
-#ifdef CONFIG_EROFS_FS_ONDEMAND
 		kfree(ctx->domain_id);
 		ctx->domain_id = kstrdup(param->string, GFP_KERNEL);
 		if (!ctx->domain_id)
 			return -ENOMEM;
-#else
-		errorfc(fc, "domain_id option not supported");
-#endif
 		break;
+#else
+	case Opt_fsid:
+	case Opt_domain_id:
+		errorfc(fc, "%s option not supported", erofs_fs_parameters[opt].name);
+		break;
+#endif
 	default:
 		return -ENOPARAM;
 	}

fs/erofs/zdata.c

@@ -1032,12 +1032,12 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
 
 	if (!be->decompressed_pages)
 		be->decompressed_pages =
-			kvcalloc(be->nr_pages, sizeof(struct page *),
-				 GFP_KERNEL | __GFP_NOFAIL);
+			kcalloc(be->nr_pages, sizeof(struct page *),
+				GFP_KERNEL | __GFP_NOFAIL);
 	if (!be->compressed_pages)
 		be->compressed_pages =
-			kvcalloc(pclusterpages, sizeof(struct page *),
-				 GFP_KERNEL | __GFP_NOFAIL);
+			kcalloc(pclusterpages, sizeof(struct page *),
+				GFP_KERNEL | __GFP_NOFAIL);
 
 	z_erofs_parse_out_bvecs(be);
 	err2 = z_erofs_parse_in_bvecs(be, &overlapped);
@@ -1085,7 +1085,7 @@ out:
 	}
 	if (be->compressed_pages < be->onstack_pages ||
 	    be->compressed_pages >= be->onstack_pages + Z_EROFS_ONSTACK_PAGES)
-		kvfree(be->compressed_pages);
+		kfree(be->compressed_pages);
 	z_erofs_fill_other_copies(be, err);
 
 	for (i = 0; i < be->nr_pages; ++i) {
@@ -1104,7 +1104,7 @@ out:
 	}
 
 	if (be->decompressed_pages != be->onstack_pages)
-		kvfree(be->decompressed_pages);
+		kfree(be->decompressed_pages);
 
 	pcl->length = 0;
 	pcl->partial = true;

fs/erofs/zmap.c

@@ -793,12 +793,16 @@ static int z_erofs_iomap_begin_report(struct inode *inode, loff_t offset,
 		iomap->type = IOMAP_HOLE;
 		iomap->addr = IOMAP_NULL_ADDR;
 		/*
-		 * No strict rule how to describe extents for post EOF, yet
-		 * we need do like below. Otherwise, iomap itself will get
+		 * No strict rule on how to describe extents for post EOF, yet
+		 * we need to do like below. Otherwise, iomap itself will get
 		 * into an endless loop on post EOF.
+		 *
+		 * Calculate the effective offset by subtracting extent start
+		 * (map.m_la) from the requested offset, and add it to length.
+		 * (NB: offset >= map.m_la always)
 		 */
 		if (iomap->offset >= inode->i_size)
-			iomap->length = length + map.m_la - offset;
+			iomap->length = length + offset - map.m_la;
 	}
 	iomap->flags = 0;
 	return 0;