On Fri, Apr 07, 2017 at 08:03:55PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> The function block_to_bt plays an integral role in determining the btree
> geometry of a block that we want to manipulate with the debugger.
> Normally we use the block magic to find the geometry profile, but if the
> magic is bad we'll never find it and return NULL. The callers of this
> function do not check for NULL and crash.
>
> Therefore, if we can't find a geometry profile matching the magic
> number, use the iocursor type to guess the profile and scowl about that
> to stdout. This makes it so that even with a corrupt magic we can try
> to print the fields instead of crashing the debugger.
....
> +#define M(a,b) (!xfs_sb_version_hascrc(&mp->m_sb) ? (a) : (b))
> + switch (iocur_top->typ->typnm) {
> + case TYP_BMAPBTA:
> + case TYP_BMAPBTD:
> + magic = M(XFS_BMAP_MAGIC, XFS_BMAP_CRC_MAGIC);
> + break;
That's really quite special, Darrick. :P
This:
(!xfs_sb_version_hascrc(&mp->m_sb) ? (a) : (b))
Could written more simply as:
(xfs_sb_version_hascrc(&mp->m_sb) ? (b) : (a))
or you could swap the macro args so you only need to drop the
negation.
Even better, though, would be to use a local variable to only
evaluate the CRC status once and kill the macro altogether:
has_crc = xfs_sb_version_hascrc(&mp->m_sb);
switch (iocur_top->typ->typnm) {
case TYP_BMAPBTA:
case TYP_BMAPBTD:
magic = has_crc ? XFS_ABTB_CRC_MAGIC : XFS_ABTB_MAGIC;
break;
.....
-Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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