Messages in this thread Patch in this message | | | Date | Wed, 11 Aug 2010 16:53:52 -0700 | From | Greg KH <> | Subject | [011/111] splice: fix misuse of SPLICE_F_NONBLOCK |
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2.6.32-stable review patch. If anyone has any objections, please let us know.
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From: Miklos Szeredi <miklos@szeredi.hu>
commit 6965031d331a642e31278fa1b5bd47f372ffdd5d upstream.
SPLICE_F_NONBLOCK is clearly documented to only affect blocking on the pipe. In __generic_file_splice_read(), however, it causes an EAGAIN if the page is currently being read.
This makes it impossible to write an application that only wants failure if the pipe is full. For example if the same process is handling both ends of a pipe and isn't otherwise able to determine whether a splice to the pipe will fill it or not.
We could make the read non-blocking on O_NONBLOCK or some other splice flag, but for now this is the simplest fix.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Jens Axboe <jaxboe@fusionio.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/splice.c | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-)
--- a/fs/splice.c +++ b/fs/splice.c @@ -365,17 +365,7 @@ __generic_file_splice_read(struct file * * If the page isn't uptodate, we may need to start io on it */ if (!PageUptodate(page)) { - /* - * If in nonblock mode then dont block on waiting - * for an in-flight io page - */ - if (flags & SPLICE_F_NONBLOCK) { - if (!trylock_page(page)) { - error = -EAGAIN; - break; - } - } else - lock_page(page); + lock_page(page); /* * Page was truncated, or invalidated by the
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