IDE: Make taskfile interface more robust wrt unexpected end-of-command

Now that we handle all the special commands using REQ_TYPE_ATA_TASKFILE
rather than using the old REQ_TYPE_ATA_CMD model, we need to also
emulate the lack of full taskfile data that comes with the old command
model (ie when commands are generated with the HDIO_DRIVE_CMD ioctl
rather than using the HDIO_DRIVE_TASK[FILE] ioctls).

In particular, this means that we should handle command completion the
more relaxed way that the old drive_cmd_intr() code did.  It allows
commands to finish early even if they don't use up all the data that we
thought we had for them.

This fixes a regression seen by Anders Eriksson where some SMART
commands sent by smartd would cause a boot-time system hang on his
machine because the IDE command handling code didn't realize that the
command had completed.

Tested-by: Anders Eriksson <aeriksson@fastmail.fm>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 9 deletions

diff --git a/drivers/ide/ide-taskfile.c b/drivers/ide/ide-taskfile.c
index 0518a2e948cf..4c86a8d84b4c 100644
--- a/drivers/ide/ide-taskfile.c
+++ b/drivers/ide/ide-taskfile.c
@@ -423,6 +423,25 @@ void task_end_request(ide_drive_t *drive, struct request *rq, u8 stat)
 }
 
 /*
+ * We got an interrupt on a task_in case, but no errors and no DRQ.
+ *
+ * It might be a spurious irq (shared irq), but it might be a
+ * command that had no output.
+ */
+static ide_startstop_t task_in_unexpected(ide_drive_t *drive, struct request *rq, u8 stat)
+{
+        /* Command all done? */
+        if (OK_STAT(stat, READY_STAT, BUSY_STAT)) {
+                task_end_request(drive, rq, stat);
+                return ide_stopped;
+        }
+
+        /* Assume it was a spurious irq */
+        ide_set_handler(drive, &task_in_intr, WAIT_WORSTCASE, NULL);
+        return ide_started;
+}
+
+/*
  * Handler for command with PIO data-in phase (Read/Read Multiple).
  */
 static ide_startstop_t task_in_intr(ide_drive_t *drive)
@@ -431,18 +450,17 @@ static ide_startstop_t task_in_intr(ide_drive_t *drive)
         struct request *rq = HWGROUP(drive)->rq;
         u8 stat = ide_read_status(drive);
 
-        /* new way for dealing with premature shared PCI interrupts */
-        if (!OK_STAT(stat, DRQ_STAT, BAD_R_STAT)) {
-                if (stat & (ERR_STAT | DRQ_STAT))
-                        return task_error(drive, rq, __FUNCTION__, stat);
-                /* No data yet, so wait for another IRQ. */
-                ide_set_handler(drive, &task_in_intr, WAIT_WORSTCASE, NULL);
-                return ide_started;
-        }
+        /* Error? */
+        if (stat & ERR_STAT)
+                return task_error(drive, rq, __FUNCTION__, stat);
+
+        /* Didn't want any data? Odd. */
+        if (!(stat & DRQ_STAT))
+                return task_in_unexpected(drive, rq, stat);
 
         ide_pio_datablock(drive, rq, 0);
 
-        /* If it was the last datablock check status and finish transfer. */
+        /* Are we done? Check status and finish transfer. */
         if (!hwif->nleft) {
                 stat = wait_drive_not_busy(drive);
                 if (!OK_STAT(stat, 0, BAD_STAT))