From: Milosz Tanski <[email protected]> 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 <[email protected]> Reviewed-by: Christoph Hellwig <[email protected]> Reviewed-by: Jeff Moyer <[email protected]> Acked-by: Sage Weil <[email protected]> --- mm/filemap.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index 3df0a57cd48e..d021931c8e74 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
