diff options
Diffstat (limited to 'fs/xfs/xfs_super.c')
| -rw-r--r-- | fs/xfs/xfs_super.c | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index 108d0d6865a6..4b31bce078c9 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -1690,13 +1690,23 @@ xfs_fs_fill_super( if (xfs_has_reflink(mp)) { /* - * Reflink doesn't support rt extent sizes larger than a single - * block because we would have to perform unshare-around for - * rtext-unaligned write requests. + * Reflink doesn't support pagecache pages that span multiple + * realtime extents because iomap doesn't track subpage dirty + * state. This means that we cannot dirty all the pages + * backing an rt extent without dirtying the adjoining rt + * extents. If those rt extents are shared and extend into + * other pages, this leads to crazy write amplification. The + * VFS remap_range checks assume power-of-two block sizes, so + * we don't support that either. + * + * Hence we only support rt extent sizes that are an integer + * power of two because we know those will align with the page + * size. */ - if (xfs_has_realtime(mp) && mp->m_sb.sb_rextsize != 1) { + if (xfs_has_realtime(mp) && + !is_power_of_2(mp->m_sb.sb_rextsize)) { xfs_alert(mp, - "reflink not compatible with realtime extent size %u!", + "reflink not compatible with non-power-of-2 realtime extent size %u!", mp->m_sb.sb_rextsize); error = -EINVAL; goto out_filestream_unmount; @@ -1715,7 +1725,6 @@ xfs_fs_fill_super( } } - error = xfs_mountfs(mp); if (error) goto out_filestream_unmount; |