There are two sites where the flag is being changed: ide_retry_pc
and idetape_do_request. Both codepaths are protected by hwif->busy
(ide_lock_port) and therefore we shouldn't need the atomic accesses. The
only problem would be the compiler reordering the accesses, therefore the
optimization barrier.
Spotted-by: Jiri Slaby <jirislaby@xxxxxxxxx>
Signed-off-by: Borislav Petkov <petkovbb@xxxxxxxxx>
---
drivers/ide/ide-atapi.c | 2 +-
drivers/ide/ide-tape.c | 21 ++++++++++++++++-----
2 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c
index afe5a43..fbcb851 100644
--- a/drivers/ide/ide-atapi.c
+++ b/drivers/ide/ide-atapi.c
@@ -258,7 +258,7 @@ void ide_retry_pc(ide_drive_t *drive)
pc->req_xfer = sense_rq->data_len;
if (drive->media == ide_tape)
- set_bit(IDE_AFLAG_IGNORE_DSC, &drive->atapi_flags);
+ drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;
if (ide_queue_sense_rq(drive, pc))
ide_complete_rq(drive, -EIO, blk_rq_bytes(drive->hwif->rq));
diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index 203bbea..4ff50cc 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -656,15 +656,24 @@ static ide_startstop_t idetape_do_request(ide_drive_t *drive,
if ((drive->dev_flags & IDE_DFLAG_DSC_OVERLAP) == 0 &&
(rq->cmd[13] & REQ_IDETAPE_PC2) == 0)
- set_bit(IDE_AFLAG_IGNORE_DSC, &drive->atapi_flags);
+ drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;
if (drive->dev_flags & IDE_DFLAG_POST_RESET) {
- set_bit(IDE_AFLAG_IGNORE_DSC, &drive->atapi_flags);
+ drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;
drive->dev_flags &= ~IDE_DFLAG_POST_RESET;
}
- if (!test_and_clear_bit(IDE_AFLAG_IGNORE_DSC, &drive->atapi_flags) &&
- (stat & ATA_DSC) == 0) {
+ /*
+ * This is a precaution for IDE_AFLAG_IGNORE_DSC being conditionally set
+ * above. We don't need a stronger enforcement of ordering because the
+ * read below cannot precede the earlier write out-of-order since it is
+ * to the same location. Also, since we have the ide port locked during
+ * the ->do_request(), we only have to be aware of gcc reordering stuff.
+ */
+ barrier();
+
+ if (!(drive->atapi_flags & IDE_AFLAG_IGNORE_DSC) &&
+ !(stat & ATA_DSC)) {
if (postponed_rq == NULL) {
tape->dsc_polling_start = jiffies;
tape->dsc_poll_freq = tape->best_dsc_rw_freq;
@@ -684,7 +693,9 @@ static ide_startstop_t idetape_do_request(ide_drive_t *drive,
tape->dsc_poll_freq = IDETAPE_DSC_MA_SLOW;
idetape_postpone_request(drive);
return ide_stopped;
- }
+ } else
+ drive->atapi_flags &= ~IDE_AFLAG_IGNORE_DSC;
+
if (rq->cmd[13] & REQ_IDETAPE_READ) {
pc = &tape->queued_pc;
ide_tape_create_rw_cmd(tape, pc, rq, READ_6);
--
1.6.3.1
--
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