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 <[email protected]>
---
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
-
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