[RFC] mm/gup.c: Updated return value of {get|pin}_user_pages_fast()

[Souptick Joarder]

Currently {get|pin}_user_pages_fast() have 3 return value 0, -errno
and no of pinned pages. The only case where these two functions will
return 0, is for nr_pages <= 0, which doesn't find a valid use case.
But if at all any, then a -ERRNO will be returned instead of 0, which
means {get|pin}_user_pages_fast() will have 2 return values -errno &
no of pinned pages.

Update all the callers which deals with return value 0 accordingly.

Signed-off-by: Souptick Joarder <jrdr.linux at gmail.com>
---
 arch/ia64/kernel/err_inject.c              | 2 +-
 drivers/platform/goldfish/goldfish_pipe.c  | 2 +-
 drivers/staging/gasket/gasket_page_table.c | 4 ++--
 drivers/tee/tee_shm.c                      | 2 +-
 mm/gup.c                                   | 6 +++---
 net/rds/rdma.c                             | 2 +-
 6 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/ia64/kernel/err_inject.c b/arch/ia64/kernel/err_inject.c
index 8b5b8e6b..fd72218 100644
--- a/arch/ia64/kernel/err_inject.c
+++ b/arch/ia64/kernel/err_inject.c
@@ -143,7 +143,7 @@ static DEVICE_ATTR(name, 0644, show_##name, store_##name)
 	int ret;
 
 	ret = get_user_pages_fast(virt_addr, 1, FOLL_WRITE, NULL);
-	if (ret<=0) {
+	if (ret < 0) {
 #ifdef ERR_INJ_DEBUG
 		printk("Virtual address %lx is not existing.\n",virt_addr);
 #endif
diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
index 1ab207e..831449d 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -277,7 +277,7 @@ static int goldfish_pin_pages(unsigned long first_page,
 	ret = pin_user_pages_fast(first_page, requested_pages,
 				  !is_write ? FOLL_WRITE : 0,
 				  pages);
-	if (ret <= 0)
+	if (ret < 0)
 		return -EFAULT;
 	if (ret < requested_pages)
 		*iter_last_page_size = PAGE_SIZE;
diff --git a/drivers/staging/gasket/gasket_page_table.c b/drivers/staging/gasket/gasket_page_table.c
index f6d7157..1d08e1d 100644
--- a/drivers/staging/gasket/gasket_page_table.c
+++ b/drivers/staging/gasket/gasket_page_table.c
@@ -489,11 +489,11 @@ static int gasket_perform_mapping(struct gasket_page_table *pg_tbl,
 			ret = get_user_pages_fast(page_addr - offset, 1,
 						  FOLL_WRITE, &page);
 
-			if (ret <= 0) {
+			if (ret < 0) {
 				dev_err(pg_tbl->device,
 					"get user pages failed for addr=0x%lx, offset=0x%lx [ret=%d]\n",
 					page_addr, offset, ret);
-				return ret ? ret : -ENOMEM;
+				return ret;
 			}
 			++pg_tbl->num_active_pages;
 
diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index bd679b7..2706a1f 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -230,7 +230,7 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
 	if (rc > 0)
 		shm->num_pages = rc;
 	if (rc != num_pages) {
-		if (rc >= 0)
+		if (rc > 0)
 			rc = -ENOMEM;
 		ret = ERR_PTR(rc);
 		goto err;
diff --git a/mm/gup.c b/mm/gup.c
index 50681f0..8d293ed 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2760,7 +2760,7 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
 	end = start + len;
 
 	if (end <= start)
-		return 0;
+		return -EINVAL;
 	if (unlikely(!access_ok((void __user *)start, len)))
 		return -EFAULT;
 
@@ -2805,8 +2805,8 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
  * calling get_user_pages().
  *
  * Returns number of pages pinned. This may be fewer than the number requested.
- * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
- * -errno.
+ * If nr_pages is 0 or negative, returns -errno. If no pages were pinned,
+ * returns -errno.
  */
 int get_user_pages_fast(unsigned long start, int nr_pages,
 			unsigned int gup_flags, struct page **pages)
diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index a7ae118..44b96e6 100644
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -161,7 +161,7 @@ static int rds_pin_pages(unsigned long user_addr, unsigned int nr_pages,
 		gup_flags |= FOLL_WRITE;
 
 	ret = pin_user_pages_fast(user_addr, nr_pages, gup_flags, pages);
-	if (ret >= 0 && ret < nr_pages) {
+	if (ret > 0 && ret < nr_pages) {
 		unpin_user_pages(pages, ret);
 		ret = -EFAULT;
 	}
-- 
1.9.1