[PATCH] libata: use FLUSH_EXT only when driver is larger than LBA28 limit
Many drives support LBA48 even when its capacity is smaller than
1<<28, as LBA48 is required for many functionalities. FLUSH_EXT is
mandatory for drives w/ LBA48 support.
Interestingly, at least one of such drives (ST960812A) has problems
dealing with FLUSH_EXT. It eventually completes the command but takes
around 7 seconds to finish in many cases thus drastically slowing down
IO transactions. This seems to be a firmware bug which sneaked into
production probably because no other ATA driver including linux IDE
issues FLUSH_EXT to drives which report support for LBA48 & FLUSH_EXT
but is smaller than 1<<28 blocks.
This patch adds ATA_DFLAG_FLUSH_EXT which is set iff the drive
supports LBA48 & FLUSH_EXT and is larger than LBA28 limit. Both cache
flush paths are updated to issue FLUSH_EXT only when the flag is set.
Note that the changed behavior is more inline with the rest of libata.
libata prefers shorter commands whenever possible.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Danny Kukawka <dkukawka@novell.com>
Cc: Stefan Seyfried <seife@novell.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 0d0ddea..36e233c 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -140,6 +140,7 @@
ATA_DFLAG_LBA48 = (1 << 1), /* device supports LBA48 */
ATA_DFLAG_CDB_INTR = (1 << 2), /* device asserts INTRQ when ready for CDB */
ATA_DFLAG_NCQ = (1 << 3), /* device supports NCQ */
+ ATA_DFLAG_FLUSH_EXT = (1 << 4), /* do FLUSH_EXT instead of FLUSH */
ATA_DFLAG_CFG_MASK = (1 << 8) - 1,
ATA_DFLAG_PIO = (1 << 8), /* device limited to PIO mode */