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 | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/mm/filemap.c b/mm/filemap.c
index 9865350d6b89..bb70b64ffb48 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1843,6 +1843,8 @@ 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);
@@ -1948,6 +1950,11 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
continue;
page_not_up_to_date:
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ put_page(page);
+ goto would_block;
+ }
+
/* Get exclusive access to the page ... */
error = lock_page_killable(page);
if (unlikely(error))
@@ -1967,6 +1974,12 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
goto page_ok;
}
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ unlock_page(page);
+ put_page(page);
+ goto would_block;
+ }
+
readpage:
/*
* A previous I/O error may have been due to temporary
@@ -2037,6 +2050,8 @@ 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
