iomap: use filemap_range_needs_writeback() for O_DIRECT reads

For reads, use the better variant of checking for the need to call
filemap_write_and_wait_range() when doing O_DIRECT.  This avoids falling
back to the slow path for IOCB_NOWAIT, if there are no pages to wait for
(or write out).

Link: https://lkml.kernel.org/r/20210224164455.1096727-4-axboe@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index bdd0d89bbf0a3419b8e7906602126a30a26d98f2..9398b8c31323b39278144bf8cbaa1ba5d0f94180 100644 (file)
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -487,12 +487,28 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
                if (pos >= dio->i_size)
                        goto out_free_dio;
 
+               if (iocb->ki_flags & IOCB_NOWAIT) {
+                       if (filemap_range_needs_writeback(mapping, pos, end)) {
+                               ret = -EAGAIN;
+                               goto out_free_dio;
+                       }
+                       iomap_flags |= IOMAP_NOWAIT;
+               }
+
                if (iter_is_iovec(iter))
                        dio->flags |= IOMAP_DIO_DIRTY;
        } else {
                iomap_flags |= IOMAP_WRITE;
                dio->flags |= IOMAP_DIO_WRITE;
 
+               if (iocb->ki_flags & IOCB_NOWAIT) {
+                       if (filemap_range_has_page(mapping, pos, end)) {
+                               ret = -EAGAIN;
+                               goto out_free_dio;
+                       }
+                       iomap_flags |= IOMAP_NOWAIT;
+               }
+
                /* for data sync or sync, we need sync completion processing */
                if (iocb->ki_flags & IOCB_DSYNC)
                        dio->flags |= IOMAP_DIO_NEED_SYNC;
@@ -507,14 +523,6 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
                        dio->flags |= IOMAP_DIO_WRITE_FUA;
        }
 
-       if (iocb->ki_flags & IOCB_NOWAIT) {
-               if (filemap_range_has_page(mapping, pos, end)) {
-                       ret = -EAGAIN;
-                       goto out_free_dio;
-               }
-               iomap_flags |= IOMAP_NOWAIT;
-       }
-
        if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
                ret = -EAGAIN;
                if (pos >= dio->i_size || pos + count > dio->i_size)