Re: [PATCH v5 00/22] Rewrite XIP code and add XIP support to ext4
From: Dave Chinner
Date: Thu Jan 23 2014 - 02:49:03 EST
On Wed, Jan 15, 2014 at 08:24:18PM -0500, Matthew Wilcox wrote:
> This series of patches add support for XIP to ext4. Unfortunately,
> it turns out to be necessary to rewrite the existing XIP support code
> first due to races that are unfixable in the current design.
> Since v4 of this patchset, I've improved the documentation, fixed a
> couple of warnings that a newer version of gcc emitted, and fixed a
> bug where we would read/write the wrong address for I/Os that were not
> aligned to PAGE_SIZE.
> I've dropped the PMD fault patch from this set since there are some
> places where we would need to split a PMD page and there's no way to do
> that right now. In its place, I've added a patch which attempts to add
> support for unwritten extents. I'm still in two minds about this; on the
> one hand, it's clearly a win for reads and writes. On the other hand,
> it adds a lot of complexity, and it probably isn't a win for pagefaults.
FYI, this may just be pure coincidence, but shortly after the first
boot of a machine with this patchset on 3.13 the root *ext3*
filesystem started having problems. It now gives persistent ENOSPC
errors when there's 2.3GB of space free (on a 8GB partition), even
though e2fsck says the filesystem is clean and error free.
Update: I've just removed the patchset, rebuilt the kernel and the
ENOSPC problem is still there. So it may be co-incidence, but given
that it is persistent something is screwed got screwed up in the
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