[PATCH v2 3/5] nfs: don't dirty ITER_BVEC pages read through direct I/O

From: Omar Sandoval
Date: Fri Dec 19 2014 - 22:19:44 EST


As with the generic blockdev code, kernel pages shouldn't be dirtied by
the direct I/O path.

Signed-off-by: Omar Sandoval <osandov@xxxxxxxxxxx>
---
fs/nfs/direct.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 10bf072..b6ca65c 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -88,6 +88,7 @@ struct nfs_direct_req {
struct pnfs_ds_commit_info ds_cinfo; /* Storage for cinfo */
struct work_struct work;
int flags;
+ int should_dirty; /* should we mark read pages dirty? */
#define NFS_ODIRECT_DO_COMMIT (1) /* an unstable reply was received */
#define NFS_ODIRECT_RESCHED_WRITES (2) /* write verification failed */
struct nfs_writeverf verf; /* unstable write verifier */
@@ -370,7 +371,8 @@ static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
struct nfs_page *req = nfs_list_entry(hdr->pages.next);
struct page *page = req->wb_page;

- if (!PageCompound(page) && bytes < hdr->good_bytes)
+ if (!PageCompound(page) && bytes < hdr->good_bytes &&
+ dreq->should_dirty)
set_page_dirty(page);
bytes += req->wb_bytes;
nfs_list_remove_request(req);
@@ -542,6 +544,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
dreq->inode = inode;
dreq->bytes_left = count;
dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
+ dreq->should_dirty = !iov_iter_is_bvec(iter);
l_ctx = nfs_get_lock_context(dreq->ctx);
if (IS_ERR(l_ctx)) {
result = PTR_ERR(l_ctx);
--
2.2.1

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