| Message ID | 20170401063512.25313-13-hch@lst.de (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Sat, Apr 01, 2017 at 08:34:58AM +0200, Christoph Hellwig wrote: > commit 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e upstream. > > We currently fall back from direct to buffered writes if we detect a > remaining shared extent in the iomap_begin callback. But by the time > iomap_begin is called for the potentially unaligned end block we might > have already written most of the data to disk, which we'd now write > again using buffered I/O. To avoid this reject all writes to reflinked > files before starting I/O so that we are guaranteed to only write the > data once. > > The alternative would be to unshare the unaligned start and/or end block > before doing the I/O. I think that's doable, and will actually be > required to support reflinks on DAX file system. But it will take a > little more time and I'd rather get rid of the double write ASAP. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > Reviewed-by: Brian Foster <bfoster@redhat.com> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Any specific reason you don't want this one in 4.9 as well? Just curious, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Apr 01, 2017 at 07:21:08PM +0200, Greg KH wrote:
> Any specific reason you don't want this one in 4.9 as well?
It won't quite apply as-is due to major changes in the direct I/O
code. it would be good to have, but need a slightly different approach.
I'll see if I'll have something ready for the next round of stable
updates.
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On Sat, Apr 01, 2017 at 07:21:08PM +0200, Greg KH wrote: > On Sat, Apr 01, 2017 at 08:34:58AM +0200, Christoph Hellwig wrote: > > commit 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e upstream. > > > > We currently fall back from direct to buffered writes if we detect a > > remaining shared extent in the iomap_begin callback. But by the time > > iomap_begin is called for the potentially unaligned end block we might > > have already written most of the data to disk, which we'd now write > > again using buffered I/O. To avoid this reject all writes to reflinked > > files before starting I/O so that we are guaranteed to only write the > > data once. > > > > The alternative would be to unshare the unaligned start and/or end block > > before doing the I/O. I think that's doable, and will actually be > > required to support reflinks on DAX file system. But it will take a > > little more time and I'd rather get rid of the double write ASAP. > > > > Signed-off-by: Christoph Hellwig <hch@lst.de> > > Reviewed-by: Brian Foster <bfoster@redhat.com> > > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > > Any specific reason you don't want this one in 4.9 as well? Nevermind, it's there, missed it, my fault... greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Apr 01, 2017 at 07:26:03PM +0200, Greg KH wrote:
> Nevermind, it's there, missed it, my fault...
And I forgot that I actually updated it for the context changes
already and even commented on that in the changelog..
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diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 032c8a74824a..2a695a8f4fe7 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -527,6 +527,15 @@ xfs_file_dio_aio_write( if ((iocb->ki_pos & mp->m_blockmask) || ((iocb->ki_pos + count) & mp->m_blockmask)) { unaligned_io = 1; + + /* + * We can't properly handle unaligned direct I/O to reflink + * files yet, as we can't unshare a partial block. + */ + if (xfs_is_reflink_inode(ip)) { + trace_xfs_reflink_bounce_dio_write(ip, iocb->ki_pos, count); + return -EREMCHG; + } iolock = XFS_IOLOCK_EXCL; } else { iolock = XFS_IOLOCK_SHARED; diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 32b113c4e973..e8811bd1019b 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -1026,17 +1026,7 @@ xfs_file_iomap_begin( if (error) goto out_unlock; - /* - * We're here because we're trying to do a directio write to a - * region that isn't aligned to a filesystem block. If the - * extent is shared, fall back to buffered mode to handle the - * RMW. - */ - if (!(flags & IOMAP_REPORT) && shared) { - trace_xfs_reflink_bounce_dio_write(ip, &imap); - error = -EREMCHG; - goto out_unlock; - } + ASSERT((flags & IOMAP_REPORT) || !shared); } if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) { diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h index d3d11905c55c..375c5e030e5b 100644 --- a/fs/xfs/xfs_trace.h +++ b/fs/xfs/xfs_trace.h @@ -3250,7 +3250,7 @@ DEFINE_INODE_IREC_EVENT(xfs_reflink_convert_cow); DEFINE_RW_EVENT(xfs_reflink_reserve_cow); DEFINE_RW_EVENT(xfs_reflink_allocate_cow_range); -DEFINE_INODE_IREC_EVENT(xfs_reflink_bounce_dio_write); +DEFINE_SIMPLE_IO_EVENT(xfs_reflink_bounce_dio_write); DEFINE_IOMAP_EVENT(xfs_reflink_find_cow_mapping); DEFINE_INODE_IREC_EVENT(xfs_reflink_trim_irec);