Re: [PATCH v2 19/28] iomap: Convert __iomap_zero_iter to use a folio
From: Matthew Wilcox <willy@infradead.org>
Date: 2021-12-16 20:43:59
Also in:
linux-fsdevel, linux-xfs, lkml
Subsystem:
filesystems (vfs and infrastructure), filesystems [iomap], gfs2 file system, the rest · Maintainers:
Alexander Viro, Christian Brauner, Andreas Gruenbacher, Linus Torvalds
On Thu, Dec 16, 2021 at 11:36:14AM -0800, Darrick J. Wong wrote:
quoted
+ /* gfs2 does not support large folios yet */ + if (len > PAGE_SIZE) + len = PAGE_SIZE;This is awkward -- gfs2 doesn't set the mapping flag to indicate that it supports large folios, so it should never be asked to deal with more than a page at a time. Shouldn't iomap_write_begin clamp its len argument to PAGE_SIZE at the start if the mapping doesn't have the large folios flag set?
You're right, this is awkward. And it's a bit of a beartrap for another filesystem that wants to implement ->prepare_page in the future.
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 9270db17c435..d67108489148 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c@@ -968,9 +968,6 @@ static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos, struct gfs2_sbd *sdp = GFS2_SB(inode); unsigned int blocks; - /* gfs2 does not support large folios yet */ - if (len > PAGE_SIZE) - len = PAGE_SIZE; blocks = ((pos & blockmask) + len + blockmask) >> inode->i_blkbits; return gfs2_trans_begin(sdp, RES_DINODE + blocks, 0); }
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 1a9e897ee25a..b1ded5204d1c 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c@@ -619,6 +619,9 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos, if (fatal_signal_pending(current)) return -EINTR; + if (!mapping_large_folio_support(iter->inode->i_mapping)) + len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos)); + if (page_ops && page_ops->page_prepare) { status = page_ops->page_prepare(iter->inode, pos, len); if (status)