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.
Thanks to Dave Chinner for pointing out the correct mailing list.
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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