[PATCH] libata: implement ata_exec_internal()

This patch implements ata_exec_internal() function which performs
libata internal command execution.  Previously, this was done by each
user by manually initializing a qc, issueing it, waiting for its
completion and handling errors.  In addition to obvious code
factoring, using ata_exec_internal() fixes the following bugs.

* qc not freed on issue failure
* ap->qactive clearing could race with the next internal command
* race between timeout handling and irq
* ignoring error condition not represented in tf->status

Also, qc & hardware are not accessed anymore once it's completed,
making internal commands more conformant with general semantics.
ata_exec_internal() also makes it easy to issue internal commands from
multiple threads if that becomes necessary.

This patch only implements ata_exec_internal().  A following patch
will convert all users.

Signed-off-by: Tejun Heo <htejun@gmail.com>

--

Jeff, all patches have been regenerated against upstream branch as of
today.  (575ab52a21)

Also, I took out a debug printk from ata_exec_internal (don't know how
that one got left there).  Other than that, all patches are identical
to the previous posting.

Thanks. :-)
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

include/linux/libata.h

@@ -135,6 +135,8 @@ enum {
 	ATA_TMOUT_BOOT_QUICK	= 7 * HZ,	/* hueristic */
 	ATA_TMOUT_CDB		= 30 * HZ,
 	ATA_TMOUT_CDB_QUICK	= 5 * HZ,
+	ATA_TMOUT_INTERNAL	= 30 * HZ,
+	ATA_TMOUT_INTERNAL_QUICK = 5 * HZ,
 
 	/* ATA bus states */
 	BUS_UNKNOWN		= 0,