From: Darrick J. Wong <djwong@xxxxxxxxxx>
With iomap support turned on for the pagecache, the kernel issues
writeback to directly to block devices and we no longer have to push all
those pages through the fuse device to userspace. Therefore, we don't
need the tight dirty limits (~1M) that are used for regular fuse. This
dramatically increases the performance of fuse's pagecache IO.
Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
fs/fuse/file_iomap.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/fs/fuse/file_iomap.c b/fs/fuse/file_iomap.c
index 0983eabe58ffef..6ecca237196ac4 100644
--- a/fs/fuse/file_iomap.c
+++ b/fs/fuse/file_iomap.c
@@ -606,6 +606,29 @@ bool fuse_iomap_fill_super(struct fuse_mount *fm)
}
}
+ if (fc->iomap_fileio) {
+ struct backing_dev_info *old_bdi = sb->s_bdi;
+ char *suffix = sb->s_bdev ? "-fuseblk" : "-fuse";
+ int err;
+
+ /*
+ * sb->s_bdi points to the initial private bdi. However, we
+ * want to redirect it to a new private bdi with default dirty
+ * and readahead settings because iomap writeback won't be
+ * pushing a ton of dirty data through the fuse device. If
+ * this fails we fall back to the initial fuse bdi.
+ */
+ sb->s_bdi = &noop_backing_dev_info;
+ err = super_setup_bdi_name(sb, "%u:%u%s.iomap", MAJOR(fc->dev),
+ MINOR(fc->dev), suffix);
+ if (err) {
+ sb->s_bdi = old_bdi;
+ } else {
+ bdi_unregister(old_bdi);
+ bdi_put(old_bdi);
+ }
+ }
+
/*
* Enable syncfs for iomap fuse servers so that we can send a final
* flush at unmount time. This also means that we can support
