[Skiboot] [PATCH 04/17] libflash/file: Break up MTD erase ioctl() calls

[Cyril Bur]

Unfortunately not all drivers are created equal and several drivers on
which pflash relies block in the kernel for quite some time and ignore
signals.

This is really only a problem if pflash is to perform large erases. So
don't, perform these ops in small chunks.

An in kernel fix is possible in most cases but it takes time and systems
will be running older drivers for quite some time. Since sector erases
aren't significantly slower than whole chip erases there isn't much of a
performance penalty to breaking up the erase ioctl()s.

Signed-off-by: Cyril Bur <cyril.bur at au1.ibm.com>
---
 libflash/file.c | 60 +++++++++++++++++++++++++++++++++------------------------
 1 file changed, 35 insertions(+), 25 deletions(-)

diff --git a/libflash/file.c b/libflash/file.c
index 5cea3fc5..7065eb4f 100644
--- a/libflash/file.c
+++ b/libflash/file.c
@@ -143,34 +143,44 @@ static int mtd_erase(struct blocklevel_device *bl, uint64_t dst, uint64_t len)
 	 * then lets just hope the kernel knows how to deal with it. If it
 	 * is unsupported the ioctl() will fail and we'll report that -
 	 * there is no other option.
+	 *
+	 * Furthermore, even very recent MTD layers and drivers aren't
+	 * particularly good at not blocking in the kernel. This creates
+	 * unexpected behaviour in userspace tools using these functions.
+	 * In the absence of significant work inside the kernel, we'll just
+	 * split stuff up here for convenience.
+	 * We can assume everything is aligned here.
 	 */
-	if (dst > UINT_MAX || len > UINT_MAX) {
-		struct erase_info_user64 erase_info = {
-			.start = dst,
-			.length = len
-		};
-
-		if (ioctl(file_data->fd, MEMERASE64, &erase_info) == -1) {
-			err = errno;
-			if (err == 25) /* Kernel doesn't do 64bit MTD erase ioctl() */
-				FL_DBG("Attempted a 64bit erase on a kernel which doesn't support it\n");
-			FL_ERR("%s: IOCTL to kernel failed! %s\n", __func__, strerror(err));
-			errno = err;
-			return FLASH_ERR_PARM_ERROR;
-		}
-	} else {
-		struct erase_info_user erase_info = {
-			.start = dst,
-			.length = len
-		};
-		if (ioctl(file_data->fd, MEMERASE, &erase_info) == -1) {
-			err = errno;
-			FL_ERR("%s: IOCTL to kernel failed! %s\n", __func__, strerror(err));
-			errno = err;
-			return FLASH_ERR_PARM_ERROR;
+	while (len) {
+		if (dst > UINT_MAX || len > UINT_MAX) {
+			struct erase_info_user64 erase_info = {
+				.start = dst,
+				.length = file_data->bl.erase_mask + 1
+			};
+
+			if (ioctl(file_data->fd, MEMERASE64, &erase_info) == -1) {
+				err = errno;
+				if (err == 25) /* Kernel doesn't do 64bit MTD erase ioctl() */
+					FL_DBG("Attempted a 64bit erase on a kernel which doesn't support it\n");
+				FL_ERR("%s: IOCTL to kernel failed! %s\n", __func__, strerror(err));
+				errno = err;
+				return FLASH_ERR_PARM_ERROR;
+			}
+		} else {
+			struct erase_info_user erase_info = {
+				.start = dst,
+				.length = file_data->bl.erase_mask + 1
+			};
+			if (ioctl(file_data->fd, MEMERASE, &erase_info) == -1) {
+				err = errno;
+				FL_ERR("%s: IOCTL to kernel failed! %s\n", __func__, strerror(err));
+				errno = err;
+				return FLASH_ERR_PARM_ERROR;
+			}
 		}
+		dst += file_data->bl.erase_mask + 1;
+		len -= file_data->bl.erase_mask + 1;
 	}
-
 	return 0;
 }
 
-- 
2.13.3