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    SubjectRe: [PATCH 1/2] amiga floppy: Stop sharing request queue across multiple gendisks
    On Thu, Oct 28, 2010 at 07:38:33PM +0200, Geert Uytterhoeven wrote:
    > On Thu, Sep 23, 2010 at 21:54, Vivek Goyal <vgoyal@redhat.com> wrote:
    > > o Use one request queue per gendisk instead of sharing request queue
    > >
    > > o Don't have hardware. No compile testing or run time testing done. Completely
    > >  untested.
    > >
    > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
    > > ---
    > >  drivers/block/amiflop.c |   59 ++++++++++++++++++++++++++++++++++++++--------
    > >  1 files changed, 48 insertions(+), 11 deletions(-)
    > >
    > > diff --git a/drivers/block/amiflop.c b/drivers/block/amiflop.c
    > > index 76f114f..ead8b77 100644
    > > --- a/drivers/block/amiflop.c
    > > +++ b/drivers/block/amiflop.c
    > > @@ -114,8 +114,6 @@ static unsigned long int fd_def_df0 = FD_DD_3;     /* default for df0 if it does
    > >  module_param(fd_def_df0, ulong, 0);
    > >  MODULE_LICENSE("GPL");
    > >
    > > -static struct request_queue *floppy_queue;
    > > -
    > >  /*
    > >  *  Macros
    > >  */
    > > @@ -164,6 +162,7 @@ static volatile int selected = -1;  /* currently selected drive */
    > >  static int writepending;
    > >  static int writefromint;
    > >  static char *raw_buf;
    > > +static int fdc_queue;
    > >
    > >  static DEFINE_SPINLOCK(amiflop_lock);
    > >
    > > @@ -1334,6 +1333,42 @@ static int get_track(int drive, int track)
    > >        return -1;
    > >  }
    > >
    > > +/*
    > > + * Round-robin between our available drives, doing one request from each
    > > + */
    > > +static struct request *set_next_request(void)
    > > +{
    > > +       struct request_queue *q;
    > > +       int cnt = FD_MAX_UNITS;
    > > +       struct request *rq;
    > > +
    > > +       /* Find next queue we can dispatch from */
    > > +       fdc_queue = fdc_queue + 1;
    > > +       if (fdc_queue == FD_MAX_UNITS)
    > > +               fdc_queue = 0;
    > > +
    > > +       for(cnt = FD_MAX_UNITS; cnt > 0, cnt--) {
    > > +
    > > +               if (unit[fdc_queue].type->code == FD_NODRIVE) {
    > > +                       if (++fdc_queue == FD_MAX_UNITS)
    > > +                               fdc_queue = 0;
    > > +                       cotinue;
    > > +               }
    > > +
    > > +               q = unit[fdc_queue].gendisk->queue;
    > > +               if (q) {
    > > +                       rq = blk_fetch_request(q);
    > > +                       if (rq)
    > > +                               break;
    > > +               }
    > > +
    > > +               if (++fdc_queue == FD_MAX_UNITS)
    > > +                       fdc_queue = 0;
    > > +       }
    > > +
    > > +       return rq;
    > > +}
    >
    > drivers/block/amiflop.c:1344: warning: ‘rq’ may be used uninitialized
    > in this function
    > drivers/block/ataflop.c:1402: warning: ‘rq’ may be used uninitialized
    > in this function
    >
    > Should `rq' just be initialized to NULL? I looked at
    > floppy.c:set_next_request(), but it's
    > completely different.
    >

    I think we should explicitly initialize rq=NULL so that we don't return
    a garbage value if we can't find any rq to dispatch.

    I will send a patch to fix that.

    Thanks
    Vivek
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