Messages in this thread |  | | Date | Tue, 27 Feb 2001 22:50:54 -0300 (BRT) | From | Marcelo Tosatti <> | Subject | Re: [patch] set kiobuf io_count once, instead of increment |
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On Tue, 27 Feb 2001, Robert Read wrote:
> Currently in brw_kiovec, iobuf->io_count is being incremented as each > bh is submitted, and decremented in the bh->b_end_io(). This means > io_count can go to zero before all the bhs have been submitted, > especially during a large request. This causes the end_kio_request() > to be called before all of the io is complete. > > This suggested patch against 2.4.2 sets io_count to the total amount > before the bhs are submitted, although there is probably a better way > to determine the io_count than this. > > robert > > diff -ru linux/fs/buffer.c linux-rm/fs/buffer.c > --- linux/fs/buffer.c Mon Jan 15 12:42:32 2001 > +++ linux-rm/fs/buffer.c Tue Jan 30 11:41:57 2001 > @@ -2085,6 +2085,7 @@ > offset = iobuf->offset; > length = iobuf->length; > iobuf->errno = 0; > + atomic_set(&iobuf->io_count, length/size); > > for (pageind = 0; pageind < iobuf->nr_pages; pageind++) { > map = iobuf->maplist[pageind]; > @@ -2119,8 +2120,6 @@ > bh[bhind++] = tmp; > length -= size; > offset += size; > - > - atomic_inc(&iobuf->io_count); > > submit_bh(rw, tmp); > /* > -
It seems your patch breaks bh allocation failure handling. If get_unused_buffer_head() fails, iobuf->io_count never reaches 0, so processes waiting on kiobuf_wait_for_io() will block forever.
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