linux-kernel - Re: [PATCH -next] scsi: efct: Use GFP

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Date:   Thu, 23 Dec 2021 11:56:08 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Christoph Hellwig <hch@....de>
CC:     <linux-kernel@...r.kernel.org>, <target-devel@...r.kernel.org>,
        <linux-scsi@...r.kernel.org>, <james.smart@...adcom.com>,
        <martin.petersen@...cle.com>
Subject: Re: [PATCH -next] scsi: efct: Use GFP_ATOMIC under spin lock


On 2021/12/21 22:28, Christoph Hellwig wrote:
> On Tue, Dec 21, 2021 at 07:37:06PM +0800, Yang Yingliang wrote:
>> A spin lock is taken here so we should use GFP_ATOMIC.
>>
>> Fixes: efac162a4e4d ("scsi: efct: Don't pass GFP_DMA to dma_alloc_coherent()")
> No, it does not fix that commit.  The driver did sleeping allocations
> even before the commit.
>
> But wher is "here"?  Can we look into not holding that lock over an
> allocation if it is preferable?  If not we should at least pass down
> the gfp_flags so that only the caller(s) that can't sleep pass GFP_ATOMIC.

According the comment of els_ios_lock, it's used to protect els ios 
list, I think we

can move down the spin lock like this:


--- a/drivers/scsi/elx/libefc/efc_els.c
+++ b/drivers/scsi/elx/libefc/efc_els.c
@@ -46,8 +46,6 @@ efc_els_io_alloc_size(struct efc_node *node, u32 
reqlen, u32 rsplen)

         efc = node->efc;

-       spin_lock_irqsave(&node->els_ios_lock, flags);
-
         if (!node->els_io_enabled) {
                 efc_log_err(efc, "els io alloc disabled\n");
                 spin_unlock_irqrestore(&node->els_ios_lock, flags);
@@ -88,6 +86,8 @@ efc_els_io_alloc_size(struct efc_node *node, u32 
reqlen, u32 rsplen)
                 els = NULL;
         }

+       spin_lock_irqsave(&node->els_ios_lock, flags);
+
         if (els) {
                 /* initialize fields */
                 els->els_retries_remaining = EFC_FC_ELS_DEFAULT_RETRIES;