On Sun, 24 Dec 2006 09:16:06 -0800 (PST)
Linus Torvalds <[EMAIL PROTECTED]> wrote:
>
>
> On Sun, 24 Dec 2006, Andrei Popa wrote:
>
> > On Sun, 2006-12-24 at 04:31 -0800, Andrew Morton wrote:
> > > Andrei Popa <[EMAIL PROTECTED]> wrote:
> > > > /dev/sda7 on / type ext3 (rw,noatime,nobh)
> > > >
> > > > I don't have corruption. I tested twice.
> > >
> > > This is a surprising result. Can you pleas retest ext3
> > > data=writeback,nobh?
> >
> > Yes, no corruption. Also tested only with data=writeback and had no
> > corruption.
>
> Ok, so it would seem to be writeback related _somehow_. However, most of
> the differences (I _thought_) in ext3 actually show up only if you have
> *both* "nobh" and "data=writeback", and as far as I can tell, just a
> simple "data=writeback" should still use the bog-standard
> "block_write_full_page()".
>
> Andrew?
>
> Although as far as I can see, then ext2 should work as-is too (since it
> too also just uses "block_write_full_page()" without anything fancy).
ext2 uses the multipage-bio assembly code for writeback whereas ext3
doesn't. But ext3 doesn't use that code in data=ordered mode, of course.
Still, this:
--- a/fs/ext2/inode.c~a
+++ a/fs/ext2/inode.c
@@ -693,7 +693,7 @@ const struct address_space_operations ex
.commit_write = generic_commit_write,
.bmap = ext2_bmap,
.direct_IO = ext2_direct_IO,
- .writepages = ext2_writepages,
+// .writepages = ext2_writepages,
.migratepage = buffer_migrate_page,
};
@@ -711,7 +711,7 @@ const struct address_space_operations ex
.commit_write = nobh_commit_write,
.bmap = ext2_bmap,
.direct_IO = ext2_direct_IO,
- .writepages = ext2_writepages,
+// .writepages = ext2_writepages,
.migratepage = buffer_migrate_page,
};
_
will switch it off for ext2.
> Strange.
>
> How about this particularly stupid diff? (please test with something that
> _would_ cause corruption normally).
>
> It is _entirely_ untested, but what it tries to do is to simply serialize
> any writeback in progress with any process that tries to re-map a shared
> page into its address space and dirty it. I haven't tested it, and maybe
> it misses some case, but it looks likea good way to try to avoid races
> with marking pages dirty and the writeback phase ..
>
> Linus
> ---
> diff --git a/mm/memory.c b/mm/memory.c
> index 563792f..64ed10b 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1544,6 +1544,7 @@ static int do_wp_page(struct mm_struct *mm, struct
> vm_area_struct *vma,
> if (!pte_same(*page_table, orig_pte))
> goto unlock;
> }
> + wait_on_page_writeback(old_page);
> dirty_page = old_page;
> get_page(dirty_page);
> reuse = 1;
> @@ -2215,6 +2216,7 @@ retry:
> page_cache_release(new_page);
> return VM_FAULT_SIGBUS;
> }
> + wait_on_page_writeback(new_page);
> }
> }
yup. Also, we could perhaps lock the target page during pagefaults..
-
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