From 9f7fe1b83fcc508dc3e05815d03dbbb752a1cfba Mon Sep 17 00:00:00 2001 From: Karel Zak Date: Fri, 1 Jun 2018 12:16:19 +0200 Subject: [PATCH 63/63] 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=1946921 Upstream: http://github.com/karelzak/util-linux/commit/816773b475900909d42c2c8282a6ac50252cac22 Signed-off-by: Karel Zak --- libmount/src/context.c | 5 +++++ libmount/src/context_mount.c | 25 ++++++++++++++++++++++--- libmount/src/optstr.c | 9 ++++++--- 3 files changed, 33 insertions(+), 6 deletions(-) diff --git a/libmount/src/context.c b/libmount/src/context.c index e7f1ee934..8e00b75a9 100644 --- a/libmount/src/context.c +++ b/libmount/src/context.c @@ -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) diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c index b88e60507..a8e84127c 100644 --- a/libmount/src/context_mount.c +++ b/libmount/src/context_mount.c @@ -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; } diff --git a/libmount/src/optstr.c b/libmount/src/optstr.c index 8248f0dee..cc077ffd9 100644 --- a/libmount/src/optstr.c +++ b/libmount/src/optstr.c @@ -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; -- 2.31.1