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From: Jiri Kosina <jikos@jikos.cz>
To: "Ananiev, Leonid I" <leonid.i.ananiev@intel.com>
Cc: linux-kernel@vger.kernel.org, linux-aio <linux-aio@kvack.org>,
	Andrew Morton <akpm@osdl.org>, Zach Brown <zach.brown@oracle.com>,
	suparna@in.ibm.com, Chris Mason <chris.mason@oracle.com>,
	Badari Pulavarty <pbadari@us.ibm.com>, Jan Kara <jack@suse.cz>
Subject: Re: [PATCH] aio: fix kernel bug when page is  temporally busy
Date: Fri, 9 Feb 2007 10:54:36 +0100 (CET)	[thread overview]
Message-ID: <Pine.LNX.4.64.0702091042330.25686@twin.jikos.cz> (raw)
In-Reply-To: <B41635854730A14CA71C92B36EC22AAC8048C3@mssmsx411>

On Fri, 9 Feb 2007, Ananiev, Leonid I wrote:

> Fix "Kernel BUG at fs/aio.c:509". Return EIOCBRETRY but not  EIO if page
> is busy.

I am currently also hunting in this area, and I think there is something 
strange in generic_file_aio_read(). This seems strange:

	for (seg = 0; seg < nr_segs; seg++) {
		read_descriptor_t desc;

		desc.written = 0;
		desc.arg.buf = iov[seg].iov_base;
		desc.count = iov[seg].iov_len;
		if (desc.count == 0)
			continue;
		desc.error = 0;
                        
		do_generic_file_read(filp,ppos,&desc,file_read_actor);
		retval += desc.written;
		if (desc.error) {
			retval = retval ?: desc.error;
			break;
		}
	}

So this code propagates desc.error back to caller _only if_ all of the 
previous segments had desc.written == 0. Which is bogus - we need to 
propagate -EIOCBRETRY as soon as any of the do_generic_file_read() 
returned it, so that the caller is aware of requests being queued.

I think something like this would be appropriate

[PATCH] AIO: handle return value from do_generic_file_read() properly

generic_file_aio_read() doesn't always propagate error return value from 
do_generic_file_read(). Namely handling of -EIOCBRETRY is important, because
aio_run_iocb() relies on this return value being always properly propagated
to it.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>

--- 

 mm/filemap.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 8332c77..5ce76ce 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1204,7 +1204,7 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 			do_generic_file_read(filp,ppos,&desc,file_read_actor);
 			retval += desc.written;
 			if (desc.error) {
-				retval = retval ?: desc.error;
+				retval = desc.error;
 				break;
 			}
 		}

-- 
Jiri Kosina

  parent reply	other threads:[~2007-02-09  9:56 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-09  4:29 Ananiev, Leonid I
2007-02-09  4:35 ` Andrew Morton
2007-02-09  5:41   ` Ananiev, Leonid I
2007-02-09  5:52     ` Andrew Morton
2007-02-12 22:52       ` Ananiev, Leonid I
2007-02-12 23:21       ` Ananiev, Leonid I
2007-02-09  7:16     ` Suparna Bhattacharya
2007-02-09  9:52       ` Ananiev, Leonid I
2007-02-09 10:11         ` Jiri Kosina
2007-02-10 18:05         ` Ken Chen
2007-02-10 18:17           ` Ananiev, Leonid I
2007-02-10 18:27           ` Ananiev, Leonid I
2007-02-10 21:57           ` Ananiev, Leonid I
2007-02-15  9:16           ` Ananiev, Leonid I
2007-02-15 18:25             ` Zach Brown
2007-02-15 19:11               ` Ananiev, Leonid I
2007-02-15 19:22                 ` Zach Brown
2007-02-15 21:06                   ` Ananiev, Leonid I
2007-02-15 23:32                   ` Ananiev, Leonid I
2007-02-16  0:01                     ` Zach Brown
2007-02-16 12:18                       ` Ananiev, Leonid I
2007-02-09  9:54 ` Jiri Kosina [this message]
2007-02-09 10:14   ` Andrew Morton
2007-02-09 10:40     ` Jiri Kosina
2007-02-09 11:05       ` Suparna Bhattacharya
2007-02-09 11:18         ` Ananiev, Leonid I
2007-02-09 17:02         ` Zach Brown
2007-02-10 19:36 Ananiev, Leonid I
2007-02-14 17:51 Ananiev, Leonid I
2007-02-15  3:30 ` Andrew Morton
2007-02-15  5:26   ` Ananiev, Leonid I

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