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Date: Mon, 28 Apr 2008 06:37:19 -0400 From: Christoph Hellwig <hch@...radead.org> To: Takashi Sato <t-sato@...jp.nec.com> Cc: "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>, "xfs@....sgi.com" <xfs@....sgi.com>, "dm-devel@...hat.com" <dm-devel@...hat.com>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [RFC PATCH 1/3] Implement generic freeze feature On Mon, Apr 28, 2008 at 07:31:23PM +0900, Takashi Sato wrote: > + /* Initialize semaphore for freeze. */ > + sema_init(&bdev->bd_freeze_sem, 1); The freezing process is already protected by bd_mount_sem, so I don't think there's need for another one. > --- linux-2.6.25.org/fs/buffer.c 2008-04-17 11:49:44.000000000 +0900 > +++ linux-2.6.25-freeze/fs/buffer.c 2008-04-24 20:43:28.000000000 +0900 > @@ -201,6 +201,19 @@ struct super_block *freeze_bdev(struct b > { > struct super_block *sb; > > + down(&bdev->bd_freeze_sem); > + sb = get_super_without_lock(bdev); > + > + /* If super_block has been already frozen, return. */ > + if (sb && sb->s_frozen != SB_UNFROZEN) { > + put_super(sb); > + up(&bdev->bd_freeze_sem); > + return sb; > + } > + > + if (sb) > + put_super(sb); > + > down(&bdev->bd_mount_sem); > sb = get_super(bdev); I think the protection against double freezes would be better done by using a trylock on bd_mount_sem. In fact after that it could be changed from a semaphore to a simple test_and_set_bit. > error = -ENOTTY; > break; > + > + case FIFREEZE: { This would be better to split intot a small helper ala ioctl_fibmap() > + case FITHAW: { Same here. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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