[patch 042/178] mm: use filemap_range_needs_writeback() for O_DIRECT reads

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From: Jens Axboe <axboe@xxxxxxxxx>
Subject: mm: use filemap_range_needs_writeback() for O_DIRECT reads

For the generic page cache read helper, use the better variant of checking
for the need to call filemap_write_and_wait_range() when doing O_DIRECT
reads.  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/20210224164455.1096727-3-axboe@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/filemap.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/filemap.c~mm-use-filemap_range_needs_writeback-for-o_direct-reads
+++ a/mm/filemap.c
@@ -2681,8 +2681,8 @@ generic_file_read_iter(struct kiocb *ioc
 
 		size = i_size_read(inode);
 		if (iocb->ki_flags & IOCB_NOWAIT) {
-			if (filemap_range_has_page(mapping, iocb->ki_pos,
-						   iocb->ki_pos + count - 1))
+			if (filemap_range_needs_writeback(mapping, iocb->ki_pos,
+						iocb->ki_pos + count - 1))
 				return -EAGAIN;
 		} else {
 			retval = filemap_write_and_wait_range(mapping,
_




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