[lkml]   [2018]   [Oct]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] fs: ufs: Remove switch statement from ufs_set_de_type function
On Sun, Oct 21, 2018 at 1:27 AM Matthew Wilcox <> wrote:
> On Sat, Oct 20, 2018 at 11:09:57PM +0100, Phillip Potter wrote:
> > 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. It is expected that for *nix compatibility
> > reasons, the relation between S_IFx and DT_x will not change. For
> > cases where the mode is invalid, upper layer validation catches this
> > anyway, so this improves readability and arguably performance by
> > assigning (mode & S_IFMT) >> 12 directly without any jump table
> > or conditional logic.
> Shouldn't we also do this for other filesystems? A quick scan suggests
> someone should at least look at xfs, ubifs, squashfs, romfs, ocfs2,
> nilfs2, hfsplus, f2fs, ext4, ext2, exofs, coda, cifs & btrfs.

I've tried to do that 2 years ago, not even for readability, but to
fix a lurking
bug in conversion table implementation that was copy&pasted from ext2 to
many other fs:

The push back from ext4/xfs maintainers was that while all fs use common
values to encode d_type in on disk format, those on-disk format values
are private to the fs.

Eventually, the fix that got merged (only to xfs) did the opposite, it converted
the conversion table lookup to a switch statement:

Some fs maintainers were happy about the initial version, but I did not
pursue pushing that cleanup:

Phillip, you are welcome to re-spin those patches if you like.
Note that the generic conversion helpers do not rely on upper layer
to catch invalid mode values.


 \ /
  Last update: 2018-10-21 07:31    [W:0.074 / U:21.960 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site