[fuse-devel] [PATCH 3/4] fuse: writepage: update bdi writeout when deleting secondary request

[Maxim P. <MPa...@pa...>]

BDI_WRITTEN counter is used to estimate bdi bandwidth. It must be incremented
every time as bdi ends page writeback. No matter whether it was fulfilled by
actual write or by discarding the request (e.g. due to shrunk i_size).

Note that even before writepages patches, the case "Got truncated off
completely" was handled in fuse_send_writepage() by calling
fuse_writepage_finish() which updated BDI_WRITTEN unconditionally.

Signed-off-by: Maxim Patlasov <MPa...@pa...>
---
 fs/fuse/file.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index a3c7123..5d323bd 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1536,6 +1536,7 @@ static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req)
 			drop->inode->i_mapping->backing_dev_info;
 		dec_bdi_stat(bdi, BDI_WRITEBACK);
 		dec_zone_page_state(drop->pages[0], NR_WRITEBACK_TEMP);
+		bdi_writeout_inc(bdi);
 		fuse_writepage_free(fc, drop);
 		fuse_put_request(fc, drop);
 		drop = next;
@@ -1706,11 +1707,14 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req,
 
 	if (old_req->num_pages == 1 && (old_req->state == FUSE_REQ_INIT ||
 					old_req->state == FUSE_REQ_PENDING)) {
+		struct backing_dev_info *bdi = page->mapping->backing_dev_info;
+
 		copy_highpage(old_req->pages[0], page);
 		spin_unlock(&fc->lock);
 
-		dec_bdi_stat(page->mapping->backing_dev_info, BDI_WRITEBACK);
+		dec_bdi_stat(bdi, BDI_WRITEBACK);
 		dec_zone_page_state(page, NR_WRITEBACK_TEMP);
+		bdi_writeout_inc(bdi);
 		fuse_writepage_free(fc, new_req);
 		fuse_request_free(new_req);
 		goto out;