Hi all, This is an alternate/iomap based variant of the XFS fix posted here: https://lore.kernel.org/linux-xfs/20201007143509.669729-1-bfoster@xxxxxxxxxx/ This addresses a post-eof stale data exposure problem that can occur when truncate down races with writeback of the new EOF page and the new EOF block happens to be unwritten. Instead of explicitly flushing the new EOF page in XFS, however, this variant updates iomap zero range to check for and zero preexisting dirty pages over unwritten extents. This reuses the dirty page checking that seek data/hole already implements for unwritten extents. Patch 1 is technically not required, but fixes an odd behavior I noticed when playing around with zero range. Without it, a zero range (with patch 2) over a large, cached (but clean), unwritten mapping would unnecessarily zero pages that aren't otherwise dirty. I don't think this is actually a problem in practice today as most large zero range requests are truncates over post-eof space (which shouldn't have page cache), but it seemed odd regardless. Thoughts, reviews, flames appreciated. Brian Brian Foster (2): iomap: use page dirty state to seek data over unwritten extents iomap: zero cached pages over unwritten extents on zero range fs/iomap/buffered-io.c | 39 +++++++++++++++++++++++++++++++++++++-- fs/iomap/seek.c | 7 ++++--- include/linux/iomap.h | 2 ++ 3 files changed, 43 insertions(+), 5 deletions(-) -- 2.25.4
