On Wed, Dec 05, 2012 at 03:02:58PM +0100, Damian Lukowski wrote:
> Hello,
>
> I would like to point out that xfs-code may need a review, whether
> it is affected by compiler issues as described in [1]. There has
> been a patch [2] for btrfs this year summarizing the problem as
> follows:
>
> On ia64, powerpc64 and sparc64 the bitfield is modified through a
> RMW cycle and current gcc rewrites the adjacent 4B word, which in
> case of a spinlock or atomic has disaterous effect.
>
> In xfs_aops.h we have
> >typedef struct xfs_ioend {
> > struct xfs_ioend *io_list;
> > unsigned int io_type;
> > int io_error;
> > atomic_t io_remaining;
> > unsigned int io_isasync : 1;
> > unsigned int io_isdirect : 1;
> >[...]
>
> where atomic_t, io_isasync and io_isdirect presumably share a common
> 8B word. I only found this occurrence so far.
Please send this to the correct list: xfs@xxxxxxxxxxx.
Cheers,
Dave.
>
> Best regards
> Damian Lukowski
>
> [1] https://lkml.org/lkml/2012/2/1/220
> [2] btrfs: fix structs where bitfields and spinlock/atomic share 8B
> word (commit c08782dacd7a098f2b8bca7f4a57a5b402e9e1e5)
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--
Dave Chinner
david@xxxxxxxxxxxxx
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