From: Milosz Tanski <milosz@xxxxxxxxx>
Allow generic_file_buffered_read to bail out early instead of waiting for
the page lock or reading a page if IOCB_NOWAIT is specified.
Signed-off-by: Milosz Tanski <milosz@xxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Acked-by: Sage Weil <sage@xxxxxxxxxx>
---
mm/filemap.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/mm/filemap.c b/mm/filemap.c
index 4bcfa74ad802..eed394fd331c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1937,6 +1937,8 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
page = find_get_page(mapping, index);
if (!page) {
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ goto would_block;
page_cache_sync_readahead(mapping,
ra, filp,
index, last_index - index);
@@ -1950,6 +1952,11 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
index, last_index - index);
}
if (!PageUptodate(page)) {
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ put_page(page);
+ goto would_block;
+ }
+
/*
* See comment in do_read_cache_page on why
* wait_on_page_locked is used to avoid unnecessarily
@@ -2131,6 +2138,8 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
goto readpage;
}
+would_block:
+ error = -EAGAIN;
out:
ra->prev_pos = prev_index;
ra->prev_pos <<= PAGE_SHIFT;
--
2.11.0
