ericonr
/
util-linux
mirror of https://github.com/ericonr/util-linux.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

libmount: improve MS_REC usage 

libmount allows to split one library (mount(8)) call to multiple mount(2)
syscalls, for example

   --rbind --make-rslave

in this case we have to be careful with MS_REC because the flag is
applied to multiple operations.

 # strace -e mount mount --rbind --make-rslave /mnt/A /mnt/B

Old version:

 mount("/mnt/A", "/mnt/B", 0x13ecac0, MS_MGC_VAL|MS_BIND, NULL) = 0
 mount("none", "/mnt/B", NULL, MS_REC|MS_SLAVE, NULL) = 0

Fixed version:

 mount("/mnt/A", "/mnt/B", 0x1f22ac0, MS_MGC_VAL|MS_BIND|MS_REC, NULL) = 0
 mount("none", "/mnt/B", NULL, MS_REC|MS_SLAVE, NULL) = 0

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1584443
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2018-06-01 12:16:19 +02:00
parent 4ebea84bb1
commit 816773b475
3 changed files with 33 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
libmount/src/context.c
View File

@ -1375,6 +1375,11 @@ struct libmnt_lock *mnt_context_get_lock(struct libmnt_context *cxt)
*
* both of these calls have the same effect.
*
* Be careful if you want to use MS_REC flag -- in this case the bit is applied
* to all bind/slave/etc. options. If you want to mix more propadation flags
* and/or bind, move operations than it's better to specify mount options by
* strings.
*
* Returns: 0 on success, negative number in case of error.
*/
int mnt_context_set_mflags(struct libmnt_context *cxt, unsigned long flags)

25
libmount/src/context_mount.c
View File

@ -73,6 +73,7 @@ static int init_propagation(struct libmnt_context *cxt)
char *opts = (char *) mnt_fs_get_vfs_options(cxt->fs);
size_t namesz;
struct libmnt_optmap const *maps[1];
int rec_count = 0;
if (!opts)
return 0;
@ -86,9 +87,19 @@ static int init_propagation(struct libmnt_context *cxt)
struct libmnt_addmount *ad;
int rc;
if (!mnt_optmap_get_entry(maps, 1, name, namesz, &ent)
|| !ent
|| !(ent->id & MS_PROPAGATION))
if (!mnt_optmap_get_entry(maps, 1, name, namesz, &ent) || !ent)
continue;
DBG(CXT, ul_debugobj(cxt, " checking %s", ent->name));
/* Note that MS_REC may be used for more flags, so we have to keep
* track about number of recursive options to keep the MS_REC in the
* mountflags if necessary.
*/
if (ent->id & MS_REC)
rec_count++;
if (!(ent->id & MS_PROPAGATION))
continue;
ad = mnt_new_addmount();
@ -96,13 +107,21 @@ static int init_propagation(struct libmnt_context *cxt)
return -ENOMEM;
ad->mountflags = ent->id;
DBG(CXT, ul_debugobj(cxt, " adding extra mount(2) call for %s", ent->name));
rc = mnt_context_append_additional_mount(cxt, ad);
if (rc)
return rc;
DBG(CXT, ul_debugobj(cxt, " removing %s from primary mount(2) call", ent->name));
cxt->mountflags &= ~ent->id;
if (ent->id & MS_REC)
rec_count--;
}
if (rec_count)
cxt->mountflags |= MS_REC;
return 0;
}

9
libmount/src/optstr.c
View File

@ -800,14 +800,17 @@ int mnt_optstr_apply_flags(char **optstr, unsigned long flags,
if (rc)
goto err;
}
if (!(ent->mask & MNT_INVERT))
if (!(ent->mask & MNT_INVERT)) {
fl &= ~ent->id;
if (ent->id & MS_REC)
fl |= MS_REC;
}
}
}
}
/* add missing options */
if (fl) {
/* add missing options (but ignore fl if contains MS_REC only) */
if (fl && fl != MS_REC) {
const struct libmnt_optmap *ent;
char *p;