Re: [Libguestfs] can not get the virt-sparsify code in libguestfs ?

On 09/23/22 16:19, Richard W.M. Jones wrote: > From 98f0b3565457c08d14e1f9ab2acecea003ebf6e1 Mon Sep 17 00:00:00 2001 > From: "Richard W.M. Jones" <rjones(a)redhat.com&gt; > Date: Fri, 23 Sep 2022 15:18:43 +0100 > Subject: [PATCH] options: Don't attempt to scan or open LVs if "lvm2" feature > is not available > > Reported-by: Feng Li > --- > options/decrypt.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/options/decrypt.c b/options/decrypt.c > index 6fc7760e3..e9d7d99e0 100644 > --- a/options/decrypt.c > +++ b/options/decrypt.c > @@ -205,19 +205,22 @@ inspect_do_decrypt (guestfs_h *g, struct key_store *ks) > CLEANUP_FREE_STRING_LIST char **partitions = guestfs_list_partitions (g); > CLEANUP_FREE_STRING_LIST char **lvs = NULL; > bool need_rescan; > + const char *lvm2_feature[] = { "lvm2", NULL }; > > if (partitions == NULL) > exit (EXIT_FAILURE); > > need_rescan = decrypt_mountables (g, (const char * const *)partitions, ks); > > - if (need_rescan) { > - if (guestfs_lvm_scan (g, 1) == -1) > + if (guestfs_feature_available (g, (char **) lvm2_feature) > 0) { > + if (need_rescan) { > + if (guestfs_lvm_scan (g, 1) == -1) > + exit (EXIT_FAILURE); > + } > + > + lvs = guestfs_lvs (g); > + if (lvs == NULL) > exit (EXIT_FAILURE); > + decrypt_mountables (g, (const char * const *)lvs, ks); > } > - > - lvs = guestfs_lvs (g); > - if (lvs == NULL) > - exit (EXIT_FAILURE); > - decrypt_mountables (g, (const char * const *)lvs, ks); > } So this is interesting. (1) If the problem is that guestfs_lvs() is called without checking for the lvm2 feature group first, then the bug was introduced in libguestfs-common commit 2d8c0f8d40b5 ("options: decrypt LUKS-on-LV devices", 2022-02-28). The manual indeed states that guestfs_lvs() depends on the lvm2 feature group. (2) If, however, the problem is *also* that guestfs_lvm_scan() is called without checking for said feature group, then the bug was introduced in either (2.1) super-antique libguestfs commit a232e62dcf50 ("fish: '-i' option automatically handles whole-disk encryption.", 2010-11-05), or (2.2) less antique but still historical libguestfs commit 55dfcb2211a6 ("New API: lvm_scan, deprecate vgscan (RHBZ#1602353).", 2018-07-26).

In either of those (2.*) cases, libguestfs-common commit 2d8c0f8d40b5 would only perpetuate the pre-existent bug. Put differently, the guestfs_lvm_scan() call had had its use even before libguestfs-common commit 2d8c0f8d40b5 (i.e., before LUKS-on-LV support), and it was already afflicted by the bug. Now, I'm not obsessing about this just so we can append a proper "Fixes:" line to the commit message. Instead, I think the scope of the fix (= the commit message & the code body of the patch both) depend on the above determination.

The subject line and the body in this patch suggest that guestfs_lvm_scan() should be avoided when "lvm2" is missing, but the documentation does not imply that guestfs_lvm_scan() were invalid to call in that case. And those feature group dependency statements in the manual come from the generator. Now, in "generator/actions_core.ml", a bunch of lvm2-related operations (such as "lvs" itself) specify optional = Some "lvm2"; but that is not the case with "lvm_scan". If case (1) applies, then the current patch (code & subject line) are too heavy-handed. That is, the guestfs_lvm_scan() call should not be further restricted than it currently is (depending only on "need_rescan") -- such a restriction would be inconsistent with the fact that the guestfs_lvm_scan() API does not actually depend on the "lvm2" feature group. If case (2) applies however, then, in addition to the current contents of the patch, we should make the "lvm_scan" operation depend on the lvm2 feature group, in the generator.