btrfs: add extra error messages for delalloc range related errors

All the error handling bugs I hit so far are all -ENOSPC from either:

- cow_file_range()
- run_delalloc_nocow()
- submit_uncompressed_range()

Previously when those functions failed, there is no error message at
all, making the debugging much harder.

So here we introduce extra error messages for:

- cow_file_range()
- run_delalloc_nocow()
- submit_uncompressed_range()
- writepage_delalloc() when btrfs_run_delalloc_range() failed
- extent_writepage() when extent_writepage_io() failed

One example of the new debug error messages is the following one:

 run fstests generic/750 at 2024-12-08 12:41:41
 BTRFS: device fsid 461b25f5-e240-4543-8deb-e7c2bd01a6d3 devid 1 transid 8 /dev/mapper/test-scratch1 (253:4) scanned by mount (2436600)
 BTRFS info (device dm-4): first mount of filesystem 461b25f5-e240-4543-8deb-e7c2bd01a6d3
 BTRFS info (device dm-4): using crc32c (crc32c-arm64) checksum algorithm
 BTRFS info (device dm-4): forcing free space tree for sector size 4096 with page size 65536
 BTRFS info (device dm-4): using free-space-tree
 BTRFS warning (device dm-4): read-write for sector size 4096 with page size 65536 is experimental
 BTRFS info (device dm-4): checking UUID tree
 BTRFS error (device dm-4): cow_file_range failed, root=363 inode=412 start=503808 len=98304: -28
 BTRFS error (device dm-4): run_delalloc_nocow failed, root=363 inode=412 start=503808 len=98304: -28
 BTRFS error (device dm-4): failed to run delalloc range, root=363 ino=412 folio=458752 submit_bitmap=11-15 start=503808 len=98304: -28

Which shows an error from cow_file_range() which is called inside a
nocow write attempt, along with the extra bitmap from
writepage_delalloc().

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -1254,6 +1254,15 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
 						       wbc);
 			if (ret >= 0)
 				last_finished = found_start + found_len;
+			if (unlikely(ret < 0))
+				btrfs_err_rl(fs_info,
+"failed to run delalloc range, root=%lld ino=%llu folio=%llu submit_bitmap=%*pbl start=%llu len=%u: %d",
+					     inode->root->root_key.objectid,
+					     btrfs_ino(inode),
+					     folio_pos(folio),
+					     fs_info->sectors_per_page,
+					     &bio_ctrl->submit_bitmap,
+					     found_start, found_len, ret);
 		} else {
 			/*
 			 * We've hit an error during previous delalloc range,
@@ -1546,6 +1555,13 @@ static int extent_writepage(struct folio *folio, struct btrfs_bio_ctrl *bio_ctrl
 				  PAGE_SIZE, bio_ctrl, i_size);
 	if (ret == 1)
 		return 0;
+	if (ret < 0)
+		btrfs_err_rl(fs_info,
+"failed to submit blocks, root=%lld inode=%llu folio=%llu submit_bitmap=%*pbl: %d",
+			     BTRFS_I(inode)->root->root_key.objectid,
+			     btrfs_ino(BTRFS_I(inode)),
+			     folio_pos(folio), fs_info->sectors_per_page,
+			     &bio_ctrl->submit_bitmap, ret);
 
 	bio_ctrl->wbc->nr_to_write--;
 

fs/btrfs/inode.c

@@ -1134,6 +1134,10 @@ static void submit_uncompressed_range(struct btrfs_inode *inode,
 		if (locked_folio)
 			btrfs_folio_end_lock(inode->root->fs_info, locked_folio,
 					     start, async_extent->ram_size);
+		btrfs_err_rl(inode->root->fs_info,
+		"%s failed, root=%llu inode=%llu start=%llu len=%llu: %d",
+			     __func__, btrfs_root_id(inode->root),
+			     btrfs_ino(inode), start, async_extent->ram_size, ret);
 	}
 }
 
@@ -1246,7 +1250,7 @@ out_free_reserve:
 	free_async_extent_pages(async_extent);
 	if (async_chunk->blkcg_css)
 		kthread_associate_blkcg(NULL);
-	btrfs_debug(fs_info,
+	btrfs_debug_rl(fs_info,
 "async extent submission failed root=%lld inode=%llu start=%llu len=%llu ret=%d",
 		    btrfs_root_id(root), btrfs_ino(inode), start,
 		    async_extent->ram_size, ret);
@@ -1580,6 +1584,10 @@ out_unlock:
 		btrfs_qgroup_free_data(inode, NULL, start + cur_alloc_size,
 				       end - start - cur_alloc_size + 1, NULL);
 	}
+	btrfs_err_rl(fs_info,
+		     "%s failed, root=%llu inode=%llu start=%llu len=%llu: %d",
+		     __func__, btrfs_root_id(inode->root),
+		     btrfs_ino(inode), orig_start, end + 1 - orig_start, ret);
 	return ret;
 }
 
@@ -2322,6 +2330,10 @@ error:
 		btrfs_qgroup_free_data(inode, NULL, cur_offset, end - cur_offset + 1, NULL);
 	}
 	btrfs_free_path(path);
+	btrfs_err_rl(fs_info,
+		     "%s failed, root=%llu inode=%llu start=%llu len=%llu: %d",
+		     __func__, btrfs_root_id(inode->root),
+		     btrfs_ino(inode), start, end + 1 - start, ret);
 	return ret;
 }
 

fs/btrfs/subpage.c

@@ -652,7 +652,7 @@ IMPLEMENT_BTRFS_PAGE_OPS(checked, folio_set_checked, folio_clear_checked,
 									\
 	GET_SUBPAGE_BITMAP(subpage, fs_info, name, &bitmap);		\
 	btrfs_warn(fs_info,						\
-	"dumpping bitmap start=%llu len=%u folio=%llu" #name "_bitmap=%*pbl", \
+	"dumpping bitmap start=%llu len=%u folio=%llu " #name "_bitmap=%*pbl", \
 		   start, len, folio_pos(folio),			\
 		   fs_info->sectors_per_page, &bitmap);			\
 }
@@ -717,6 +717,7 @@ void btrfs_folio_set_lock(const struct btrfs_fs_info *fs_info,
 	/* Target range should not yet be locked. */
 	if (unlikely(!bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits))) {
 		subpage_dump_bitmap(fs_info, folio, locked, start, len);
+		btrfs_warn(fs_info, "nr_locked=%u\n", atomic_read(&subpage->nr_locked));
 		ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
 	}
 	bitmap_set(subpage->bitmaps, start_bit, nbits);