From: Andrew Morton <akpm@linux-foundation.org>
To: Shaohua Li <shli@kernel.org>
Cc: linux-mm@kvack.org, Holger Kiehl <Holger.Kiehl@dwd.de>,
Hugh Dickins <hughd@google.com>
Subject: Re: [RFC]swap: don't do discard if no discard option added
Date: Tue, 20 Mar 2012 12:42:30 -0700 [thread overview]
Message-ID: <20120320124230.21990008.akpm@linux-foundation.org> (raw)
In-Reply-To: <4F68795E.9030304@kernel.org>
On Tue, 20 Mar 2012 20:34:38 +0800
Shaohua Li <shli@kernel.org> wrote:
>
> Even don't add discard option, swapon will do discard, this sounds buggy,
> especially when discard is slow or buggy.
>
That changelog is pretty hard to understand. I rewrote it as below.
From: Shaohua Li <shli@kernel.org>
Subject: swap: don't do discard if no discard option added
When swapon() was not passed the SWAP_FLAG_DISCARD option, sys_swapon()
will still perform a discard operation. This can cause problems if discard
is slow or buggy.
Reverse the order of the check so that a discard operation is performed
only if the sys_swapon() caller is attempting to enable discard.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Reported-by: Holger Kiehl <Holger.Kiehl@dwd.de>
Tested-by: Holger Kiehl <Holger.Kiehl@dwd.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/swapfile.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/swapfile.c~swap-dont-do-discard-if-no-discard-option-added mm/swapfile.c
--- a/mm/swapfile.c~swap-dont-do-discard-if-no-discard-option-added
+++ a/mm/swapfile.c
@@ -2105,7 +2105,7 @@ SYSCALL_DEFINE2(swapon, const char __use
p->flags |= SWP_SOLIDSTATE;
p->cluster_next = 1 + (random32() % p->highest_bit);
}
- if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
+ if ((swap_flags & SWAP_FLAG_DISCARD) && discard_swap(p) == 0)
p->flags |= SWP_DISCARDABLE;
}
_
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next prev parent reply other threads:[~2012-03-20 19:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-20 12:34 [RFC]swap: don't do discard if no discard option added Shaohua Li
2012-03-20 18:21 ` Holger Kiehl
2012-03-20 19:42 ` Andrew Morton [this message]
2012-03-21 3:57 ` Hugh Dickins
2012-03-21 4:31 ` Shaohua Li
2012-03-21 4:56 ` Andrew Morton
2012-03-23 11:23 ` Hugh Dickins
2012-03-23 11:00 ` Hugh Dickins
2012-03-21 17:55 ` Holger Kiehl
2012-03-23 11:38 ` Hugh Dickins
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