Merge tag 'spi-nor/for-5.19' into mtd/next

SPI NOR core changes:
- Read back written SR value to make sure the write was done correctly.
- Introduce a common function for Read ID that manufacturer drivers can
  use to verify the Octal DTR switch worked correctly.
- Add helpers for read/write any register commands so manufacturer
  drivers don't open code it every time.
- Clarify rdsr dummy cycles documentation.
- Add debugfs entry to expose internal flash parameters and state.

SPI NOR manufacturer drivers changes:
- Add support for Winbond W25Q512NW-IM, and Eon EN25QH256A.
- Move spi_nor_write_ear() to Winbond module since only Winbond flashes
  use it.
- Rework Micron and Cypress Octal DTR enable methods to improve
  readability.
- Use the common Read ID function to verify switch to Octal DTR mode for
  Micron and Cypress flashes.
- Skip polling status on volatile register writes for Micron and Cypress
  flashes since the operation is instant.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

1 files changed, 20 insertions, 11 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 529c9ad3e926..4b2fea33158e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2513,7 +2513,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		pgoff_t end_index;
 		unsigned long nr, ret;
 		loff_t i_size = i_size_read(inode);
-		bool got_page;
 
 		end_index = i_size >> PAGE_SHIFT;
 		if (index > end_index)
@@ -2570,24 +2569,34 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 			 */
 			if (!offset)
 				mark_page_accessed(page);
-			got_page = true;
+			/*
+			 * Ok, we have the page, and it's up-to-date, so
+			 * now we can copy it to user space...
+			 */
+			ret = copy_page_to_iter(page, offset, nr, to);
+			put_page(page);
+
+		} else if (iter_is_iovec(to)) {
+			/*
+			 * Copy to user tends to be so well optimized, but
+			 * clear_user() not so much, that it is noticeably
+			 * faster to copy the zero page instead of clearing.
+			 */
+			ret = copy_page_to_iter(ZERO_PAGE(0), offset, nr, to);
 		} else {
-			page = ZERO_PAGE(0);
-			got_page = false;
+			/*
+			 * But submitting the same page twice in a row to
+			 * splice() - or others? - can result in confusion:
+			 * so don't attempt that optimization on pipes etc.
+			 */
+			ret = iov_iter_zero(nr, to);
 		}
 
-		/*
-		 * Ok, we have the page, and it's up-to-date, so
-		 * now we can copy it to user space...
-		 */
-		ret = copy_page_to_iter(page, offset, nr, to);
 		retval += ret;
 		offset += ret;
 		index += offset >> PAGE_SHIFT;
 		offset &= ~PAGE_MASK;
 
-		if (got_page)
-			put_page(page);
 		if (!iov_iter_count(to))
 			break;
 		if (ret < nr) {