On Tue, 20 Nov 2012, Attilio Rao wrote:
On Tue, Nov 20, 2012 at 6:20 AM, Bruce Evans <b...@optusnet.com.au> wrote:
On Mon, 19 Nov 2012, Attilio Rao wrote:
Log:
r16312 is not any longer real since many years (likely since when VFS
received granular locking) but the comment present in UFS has been
copied all over other filesystems code incorrectly for several times.
Removes comments that makes no sense now.
It still made sense (except for bitrot in the function name), but might not
be true). The code made sense with it. Now the code makes no sense.
Modified: head/sys/ufs/ffs/ffs_vfsops.c
==============================================================================
--- head/sys/ufs/ffs/ffs_vfsops.c Mon Nov 19 21:58:14 2012
(r243310)
+++ head/sys/ufs/ffs/ffs_vfsops.c Mon Nov 19 22:43:45 2012
(r243311)
@@ -1676,14 +1676,6 @@ ffs_vgetf(mp, ino, flags, vpp, ffs_flags
ump = VFSTOUFS(mp);
dev = ump->um_dev;
fs = ump->um_fs;
-
- /*
- * If this malloc() is performed after the getnewvnode()
This malloc() didn't match the code, which uses uma_zalloc(). Old
versions used MALLOC() in both the comment and the code. ffs's comment
was updated to say malloc() when the code was changed to use malloc(),
then rotted when the code was changed to use uma_zalloc(). In some
other file systems, the comment still said MALLOC().
- * it might block, leaving a vnode with a NULL v_data to be
- * found by ffs_sync() if a sync happens to fire right then,
- * which will cause a panic because ffs_sync() blindly
- * dereferences vp->v_data (as well it should).
- */
ip = uma_zalloc(uma_inode, M_WAITOK | M_ZERO);
/* Allocate a new vnode/inode. */
The code makes no sense now. The comment explains why ip is allocated
before vp, instead of in the natural, opposite order like it used to
be. Allocating things in an unnatural order requires extra code to
free ip when the allocation of vp fails.
"Used to be" is very arguably. The code has been like its current form
many more years than the opposite (16 against 3 I think).
And the code makes perfectly sense if you know the history. So I don't
agree with you.
But it shouldn't be necessary to know the history of the code to
understand it. The code only makes sense if its comment is not removed,
or if you know the history of the code so that you can restore the
removed comment. However, if the comment makes no sense as you claim,
then the code that it it describes makes no sense.
I didn't point out before that the comment "/* Allocate a new vnode/inode. */"
does less than echo the code, since the code obviously allocates a new
vnode/inode and only the extent of the part which does that is unclear,
and the comment is disorganized so as to make the scope unclear.
Bruce
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