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Subject[PATCH 4.1 26/78] libfc: Fix fc_fcp_cleanup_each_cmd()
Date
4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@sandisk.com>

commit 8f2777f53e3d5ad8ef2a176a4463a5c8e1a16431 upstream.

Since fc_fcp_cleanup_cmd() can sleep this function must not
be called while holding a spinlock. This patch avoids that
fc_fcp_cleanup_each_cmd() triggers the following bug:

BUG: scheduling while atomic: sg_reset/1512/0x00000202
1 lock held by sg_reset/1512:
#0: (&(&fsp->scsi_pkt_lock)->rlock){+.-...}, at: [<ffffffffc0225cd5>] fc_fcp_cleanup_each_cmd.isra.21+0xa5/0x150 [libfc]
Preemption disabled at:[<ffffffffc0225cd5>] fc_fcp_cleanup_each_cmd.isra.21+0xa5/0x150 [libfc]
Call Trace:
[<ffffffff816c612c>] dump_stack+0x4f/0x7b
[<ffffffff810828bc>] __schedule_bug+0x6c/0xd0
[<ffffffff816c87aa>] __schedule+0x71a/0xa10
[<ffffffff816c8ad2>] schedule+0x32/0x80
[<ffffffffc0217eac>] fc_seq_set_resp+0xac/0x100 [libfc]
[<ffffffffc0218b11>] fc_exch_done+0x41/0x60 [libfc]
[<ffffffffc0225cff>] fc_fcp_cleanup_each_cmd.isra.21+0xcf/0x150 [libfc]
[<ffffffffc0225f43>] fc_eh_device_reset+0x1c3/0x270 [libfc]
[<ffffffff814a2cc9>] scsi_try_bus_device_reset+0x29/0x60
[<ffffffff814a3908>] scsi_ioctl_reset+0x258/0x2d0
[<ffffffff814a2650>] scsi_ioctl+0x150/0x440
[<ffffffff814b3a9d>] sd_ioctl+0xad/0x120
[<ffffffff8132f266>] blkdev_ioctl+0x1b6/0x810
[<ffffffff811da608>] block_ioctl+0x38/0x40
[<ffffffff811b4e08>] do_vfs_ioctl+0x2f8/0x530
[<ffffffff811b50c1>] SyS_ioctl+0x81/0xa0
[<ffffffff816cf8b2>] system_call_fastpath+0x16/0x7a

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/scsi/libfc/fc_fcp.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)

--- a/drivers/scsi/libfc/fc_fcp.c
+++ b/drivers/scsi/libfc/fc_fcp.c
@@ -1039,11 +1039,26 @@ restart:
fc_fcp_pkt_hold(fsp);
spin_unlock_irqrestore(&si->scsi_queue_lock, flags);

- if (!fc_fcp_lock_pkt(fsp)) {
+ spin_lock_bh(&fsp->scsi_pkt_lock);
+ if (!(fsp->state & FC_SRB_COMPL)) {
+ fsp->state |= FC_SRB_COMPL;
+ /*
+ * TODO: dropping scsi_pkt_lock and then reacquiring
+ * again around fc_fcp_cleanup_cmd() is required,
+ * since fc_fcp_cleanup_cmd() calls into
+ * fc_seq_set_resp() and that func preempts cpu using
+ * schedule. May be schedule and related code should be
+ * removed instead of unlocking here to avoid scheduling
+ * while atomic bug.
+ */
+ spin_unlock_bh(&fsp->scsi_pkt_lock);
+
fc_fcp_cleanup_cmd(fsp, error);
+
+ spin_lock_bh(&fsp->scsi_pkt_lock);
fc_io_compl(fsp);
- fc_fcp_unlock_pkt(fsp);
}
+ spin_unlock_bh(&fsp->scsi_pkt_lock);

fc_fcp_pkt_release(fsp);
spin_lock_irqsave(&si->scsi_queue_lock, flags);



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