On Wed, Oct 17, 2018 at 10:11:47AM +0000, David Laight wrote: > From: Phillip Potter > > Sent: 17 October 2018 11:08 > > > > Remove switch statement from ufs_set_de_type function in fs/ufs/util.h > > header and replace with simple assignment. For each case, S_IFx >> 12 > > is equal to DT_x, so in valid cases (mode & S_IFMT) >> 12 should give > > us the correct file type. For invalid cases, upper layer validation > > catches this anyway, so this improves readability and arguably > > performance by assigning (mode & S_IFMT) >> 12 directly. > > > ... > > - case S_IFIFO: > > - de->d_u.d_44.d_type = DT_FIFO; > > - break; > > - default: > > - de->d_u.d_44.d_type = DT_UNKNOWN; > > - } > > + de->d_u.d_44.d_type = (mode & S_IFMT) >> S_SHIFT; > > This requires that the two sets of constants are correctly aligned. They are. BSD folks had (sanely, IMO) put the 'type' bits of st_mode into directory entry verbatim. Again, "symbolic constant" != "can be expected to change"... If, e.g., some port decides to change S_IFIFO, they'll have no end of fun accessing ext*, xfs, ufs, etc. since that value is stored in the on-disk inode and in effect pinned down by that. All S_... constants are universal and going to remain unchanged on any Unices.
