[PATCH] ide: option to disable cache flushes for buggy drives

Some drives claim they support cache flushing, but get seriously
confused if you try. Add this option to be able to boot with
barriers enabled by default.

Signed-off-by: Jens Axboe <axboe@suse.de>

drivers/ide/ide-disk.c

@@ -776,7 +776,7 @@ static void update_ordered(ide_drive_t *drive)
 		 * not available so we don't need to recheck that.
 		 */
 		capacity = idedisk_capacity(drive);
-		barrier = ide_id_has_flush_cache(id) &&
+		barrier = ide_id_has_flush_cache(id) && !drive->noflush &&
 			(drive->addressing == 0 || capacity <= (1ULL << 28) ||
 			 ide_id_has_flush_cache_ext(id));
 

drivers/ide/ide.c

@@ -1539,7 +1539,7 @@ static int __init ide_setup(char *s)
 		const char *hd_words[] = {
 			"none", "noprobe", "nowerr", "cdrom", "serialize",
 			"autotune", "noautotune", "minus8", "swapdata", "bswap",
-			"minus11", "remap", "remap63", "scsi", NULL };
+			"noflush", "remap", "remap63", "scsi", NULL };
 		unit = s[2] - 'a';
 		hw   = unit / MAX_DRIVES;
 		unit = unit % MAX_DRIVES;
@@ -1578,6 +1578,9 @@ static int __init ide_setup(char *s)
 			case -10: /* "bswap" */
 				drive->bswap = 1;
 				goto done;
+			case -11: /* noflush */
+				drive->noflush = 1;
+				goto done;
 			case -12: /* "remap" */
 				drive->remap_0_to_1 = 1;
 				goto done;

include/linux/ide.h

@@ -571,6 +571,7 @@ typedef struct ide_drive_s {
 	u8	waiting_for_dma;	/* dma currently in progress */
 	u8	unmask;			/* okay to unmask other irqs */
 	u8	bswap;			/* byte swap data */
+	u8	noflush;		/* don't attempt flushes */
 	u8	dsc_overlap;		/* DSC overlap */
 	u8	nice1;			/* give potential excess bandwidth */