Re: [PATCH] [RFC] xfs: fix inode fork extent count overflow

[Dave Chinner <david@fromorbit.com>]

On Wed, Sep 11, 2019 at 03:55:51AM -0700, Christoph Hellwig wrote:
> ... and there went my hopes to eventually squeeze xfs_ifork into
> a single 64-byte cacheline.  But the analys looks sensible.

Not sure what the issue is here:

struct xfs_ifork {
        int64_t                    if_bytes;             /*     0     8 */
        struct xfs_btree_block *   if_broot;             /*     8     8 */
        unsigned int               if_seq;               /*    16     4 */
        int                        if_height;            /*    20     4 */
        union {
                void *             if_root;              /*    24     8 */
                char *             if_data;              /*    24     8 */
        } if_u1;                                         /*    24     8 */
        short int                  if_broot_bytes;       /*    32     2 */
        unsigned char              if_flags;             /*    34     1 */

        /* size: 40, cachelines: 1, members: 7 */
        /* padding: 5 */
        /* last cacheline: 40 bytes */
};

it's already well inside a 64-byte single cacheline, even with a
64bit if_bytes. Yes, I've just pushed it from 32 to 40 bytes, but
but if that is a problem we could pack some things more tightly...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com