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Message-ID: <20080820193402.GG8109@mit.edu> Date: Wed, 20 Aug 2008 15:34:02 -0400 From: Theodore Tso <tytso@....edu> To: Andreas Dilger <adilger@....com> Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>, ext4 development <linux-ext4@...r.kernel.org> Subject: Re: ENOSPC returned during writepages On Wed, Aug 20, 2008 at 01:25:36PM -0600, Andreas Dilger wrote: > What I think makes sense, however, is that if freeblocks < $threshold that > a global spinlock is taken and the percpu_counter_sum() is done under the > lock before deciding if enough space is left. Since it is impossible that > the other CPUs get below -FBC_BATCH away from the correct free space they > should all get the spinlock at the same time when we get too low. Yep, I agree. I suggested something very similar as my first suggestion. I do think though that we need to rationalize the percpu_counter interface, though; those are two separable issues, and both IMHO need fixing... The fact that we have a #ifdef CONFIG_SMP in fs/ext4/inode.c and we are doing wierd things with percpu_counter_sum and percpu_counter_sum_and_set is ugly. And it would be good if most of the time we can avoid taking the filesystem-level spinlock, and rely on the percpu_counter except when we start getting low on space. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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