At 21:59 08/08/13, Chris Mason wrote:
>On Wed, 2008-08-13 at 12:16 +0200, Jan Kara wrote:
>
>> > With that said, I don't have strong feelings against falling back to
>> > buffered IO when the invalidate fails. Maybe Zach remembers something I
>> > don't?
>> I don't have a strong opinion either. Falling back to buffered writes is
>> simpler at least for ext3/ext4 because properly synchronizing against
>> writepage() call does not seem to have a nice solution either in
>> do_launder_page() or in releasepage(). OTOH is hides the fact the invalidate
>> is failing and so if we screw up something in future and it fails often, it
>> might be hard to notice / track down the performance penalty.
>
>In general, these races don't happen often, and when they do it is
>because someone is mixing page cache and O_DIRECT io to the same file.
>That is explicitly outside the main use case of O_DIRECT.
>
>So, I'd rather see us slow down O_DIRECT in the mixed use case than have
>big impacts in complexity or speed to other parts of the kernel. If
>falling back avoids problems in some filesystems or avoids clearing the
>uptodate bit unexpectedly, I'd much rather take the fallback patch.
>
>-chris
Hi Andrew.
I think we don't have strong feelings against falling back to buffered writes to
fix the direct-io -EIO problem.
Please review my patch.
Signed-off-by: Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx>
diff -Nrup linux-2.6.27-rc3.org/mm/filemap.c linux-2.6.27-rc3/mm/filemap.c
--- linux-2.6.27-rc3.org/mm/filemap.c 2008-08-13 13:48:47.000000000 +0900
+++ linux-2.6.27-rc3/mm/filemap.c 2008-08-19 15:45:31.000000000 +0900
@@ -2129,13 +2129,20 @@ generic_file_direct_write(struct kiocb *
* After a write we want buffered reads to be sure to go to disk to get
* the new data. We invalidate clean cached page from the region we're
* about to write. We do this *before* the write so that we can return
- * -EIO without clobbering -EIOCBQUEUED from ->direct_IO().
+ * without clobbering -EIOCBQUEUED from ->direct_IO().
*/
if (mapping->nrpages) {
written = invalidate_inode_pages2_range(mapping,
pos >> PAGE_CACHE_SHIFT, end);
- if (written)
+ /*
+ * If a page can not be invalidated, return 0 to fall back
+ * to buffered write.
+ */
+ if (written) {
+ if (written == -EBUSY)
+ return 0;
goto out;
+ }
}
written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
diff -Nrup linux-2.6.27-rc3.org/mm/truncate.c linux-2.6.27-rc3/mm/truncate.c
--- linux-2.6.27-rc3.org/mm/truncate.c 2008-08-13 13:48:48.000000000 +0900
+++ linux-2.6.27-rc3/mm/truncate.c 2008-08-19 12:10:46.000000000 +0900
@@ -380,7 +380,7 @@ static int do_launder_page(struct addres
* Any pages which are found to be mapped into pagetables are unmapped prior to
* invalidation.
*
- * Returns -EIO if any pages could not be invalidated.
+ * Returns -EBUSY if any pages could not be invalidated.
*/
int invalidate_inode_pages2_range(struct address_space *mapping,
pgoff_t start, pgoff_t end)
@@ -440,7 +440,7 @@ int invalidate_inode_pages2_range(struct
ret2 = do_launder_page(mapping, page);
if (ret2 == 0) {
if (!invalidate_complete_page2(mapping, page))
- ret2 = -EIO;
+ ret2 = -EBUSY;
}
if (ret2 < 0)
ret = ret2;
--
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