Bartlomiej Zolnierkiewicz wrote:

From: Bartlomiej Zolnierkiewicz <[EMAIL PROTECTED]>
Subject: [PATCH] ide-disk: fix flush requests (take 2)

commit 813a0eb233ee67d7166241a8b389b6a76f2247f9
Author: Bartlomiej Zolnierkiewicz <[EMAIL PROTECTED]>
Date:   Fri Jan 25 22:17:10 2008 +0100

    ide: switch idedisk_prepare_flush() to use REQ_TYPE_ATA_TASKFILE requests


broke flush requests.

Allocating IDE command structure on the stack for flush requests is not
a very brilliant idea:

- idedisk_prepare_flush() only prepares the request and it doesn't wait
  for it to be completed

- there are can be multiple flush requests queued in the queue

Fix the problem (per hints from James Bottomley) by:
- dynamically allocating ide_task_t instance using kmalloc(..., GFP_ATOMIC)
- adding new taskfile flag (IDE_TFLAG_DYN)
- calling kfree() in ide_end_drive_command() if IDE_TFLAG_DYN is set
  (while at it rename 'args' to 'task' and fix whitespace damage)

[ This will be fixed properly before 2.6.25 but this bug is rather
  critical and the proper solution requires some more work + testing. ]

Thanks to Sebastian Siewior and Christoph Hellwig for reporitng the
problem and testing patches (extra thanks to Sebastian for bisecting
it to the guilty commmit).

Cc: Sebastian Siewior <[EMAIL PROTECTED]>
Cc: Christoph Hellwig <[EMAIL PROTECTED]>
Cc: James Bottomley <[EMAIL PROTECTED]>
Cc: Jens Axboe <[EMAIL PROTECTED]>
Cc: Sergei Shtylyov <[EMAIL PROTECTED]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[EMAIL PROTECTED]>

Acked-by: Sergei Shtylyov <[EMAIL PROTECTED]>

Index: b/drivers/ide/ide-disk.c
--- a/drivers/ide/ide-disk.c
+++ b/drivers/ide/ide-disk.c
@@ -590,20 +590,24 @@ static ide_proc_entry_t idedisk_proc[] =
 static void idedisk_prepare_flush(struct request_queue *q, struct request *rq)
        ide_drive_t *drive = q->queuedata;
-       ide_task_t task;
+       ide_task_t *task = kmalloc(sizeof(*task), GFP_ATOMIC);
- memset(&task, 0, sizeof(task));
+       /* FIXME: map struct ide_taskfile on rq->cmd[] */
+       BUG_ON(task == NULL);
+       memset(task, 0, sizeof(*task));

   Why not kzalloc() then?

MBR, Sergei
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