[PATCH 2/3] fs: support IOCB_NOWAIT in generic_file_buffered_read
From: Christoph Hellwig <hch@lst.de>
Date: 2017-06-30 18:15:49
Also in:
linux-fsdevel
Subsystem:
memory management, page cache, the rest · Maintainers:
Andrew Morton, Matthew Wilcox, Linus Torvalds
From: Milosz Tanski <redacted> 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 <redacted> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jeff Moyer <redacted> Acked-by: Sage Weil <redacted> --- 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