Messages in this thread Patch in this message | | | Date | Sun, 05 Feb 2012 23:09:55 +0100 | From | Willy Tarreau <> | Subject | [PATCH 06/91] put stricter guards on queue dead checks |
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2.6.27-longterm review patch. If anyone has any objections, please let us know.
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commit 86cbfb5607d4b81b1a993ff689bbd2addd5d3a9b upstream.
SCSI uses request_queue->queuedata == NULL as a signal that the queue is dying. We set this state in the sdev release function. However, this allows a small window where we release the last reference but haven't quite got to this stage yet and so something will try to take a reference in scsi_request_fn and oops. It's very rare, but we had a report here, so we're pushing this as a bug fix
The actual fix is to set request_queue->queuedata to NULL in scsi_remove_device() before we drop the reference. This causes correct automatic rejects from scsi_request_fn as people who hold additional references try to submit work and prevents anything from getting a new reference to the sdev that way.
Signed-off-by: James Bottomley <James.Bottomley@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> --- drivers/scsi/scsi_sysfs.c | 16 ++++++++-------- 1 files changed, 8 insertions(+), 8 deletions(-)
Index: longterm-2.6.27/drivers/scsi/scsi_sysfs.c =================================================================== --- longterm-2.6.27.orig/drivers/scsi/scsi_sysfs.c 2012-02-05 22:34:34.876915660 +0100 +++ longterm-2.6.27/drivers/scsi/scsi_sysfs.c 2012-02-05 22:34:35.776914691 +0100 @@ -317,14 +317,8 @@ kfree(evt); } - if (sdev->request_queue) { - sdev->request_queue->queuedata = NULL; - /* user context needed to free queue */ - scsi_free_queue(sdev->request_queue); - /* temporary expedient, try to catch use of queue lock - * after free of sdev */ - sdev->request_queue = NULL; - } + /* NULL queue means the device can't be used */ + sdev->request_queue = NULL; scsi_target_reap(scsi_target(sdev)); @@ -950,6 +944,12 @@ if (sdev->host->hostt->slave_destroy) sdev->host->hostt->slave_destroy(sdev); transport_destroy_device(dev); + + /* cause the request function to reject all I/O requests */ + sdev->request_queue->queuedata = NULL; + + /* Freeing the queue signals to block that we're done */ + scsi_free_queue(sdev->request_queue); put_device(dev); }
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