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From 9f7fe1b83fcc508dc3e05815d03dbbb752a1cfba Mon Sep 17 00:00:00 2001
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From: Karel Zak <kzak@redhat.com>
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Date: Fri, 1 Jun 2018 12:16:19 +0200
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Subject: [PATCH 63/63] libmount: improve MS_REC usage
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libmount allows to split one library (mount(8)) call to multiple mount(2)
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syscalls, for example
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--rbind --make-rslave
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in this case we have to be careful with MS_REC because the flag is
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applied to multiple operations.
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# strace -e mount mount --rbind --make-rslave /mnt/A /mnt/B
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Old version:
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mount("/mnt/A", "/mnt/B", 0x13ecac0, MS_MGC_VAL|MS_BIND, NULL) = 0
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mount("none", "/mnt/B", NULL, MS_REC|MS_SLAVE, NULL) = 0
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Fixed version:
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mount("/mnt/A", "/mnt/B", 0x1f22ac0, MS_MGC_VAL|MS_BIND|MS_REC, NULL) = 0
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mount("none", "/mnt/B", NULL, MS_REC|MS_SLAVE, NULL) = 0
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Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1946921
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Upstream: http://github.com/karelzak/util-linux/commit/816773b475900909d42c2c8282a6ac50252cac22
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Signed-off-by: Karel Zak <kzak@redhat.com>
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---
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libmount/src/context.c | 5 +++++
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libmount/src/context_mount.c | 25 ++++++++++++++++++++++---
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libmount/src/optstr.c | 9 ++++++---
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3 files changed, 33 insertions(+), 6 deletions(-)
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diff --git a/libmount/src/context.c b/libmount/src/context.c
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index e7f1ee934..8e00b75a9 100644
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--- a/libmount/src/context.c
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+++ b/libmount/src/context.c
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@@ -1375,6 +1375,11 @@ struct libmnt_lock *mnt_context_get_lock(struct libmnt_context *cxt)
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*
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* both of these calls have the same effect.
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*
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+ * Be careful if you want to use MS_REC flag -- in this case the bit is applied
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+ * to all bind/slave/etc. options. If you want to mix more propadation flags
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+ * and/or bind, move operations than it's better to specify mount options by
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+ * strings.
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+ *
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* Returns: 0 on success, negative number in case of error.
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*/
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int mnt_context_set_mflags(struct libmnt_context *cxt, unsigned long flags)
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diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c
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index b88e60507..a8e84127c 100644
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--- a/libmount/src/context_mount.c
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+++ b/libmount/src/context_mount.c
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@@ -73,6 +73,7 @@ static int init_propagation(struct libmnt_context *cxt)
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char *opts = (char *) mnt_fs_get_vfs_options(cxt->fs);
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size_t namesz;
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struct libmnt_optmap const *maps[1];
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+ int rec_count = 0;
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if (!opts)
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return 0;
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@@ -86,9 +87,19 @@ static int init_propagation(struct libmnt_context *cxt)
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struct libmnt_addmount *ad;
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int rc;
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- if (!mnt_optmap_get_entry(maps, 1, name, namesz, &ent)
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- || !ent
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- || !(ent->id & MS_PROPAGATION))
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+ if (!mnt_optmap_get_entry(maps, 1, name, namesz, &ent) || !ent)
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+ continue;
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+
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+ DBG(CXT, ul_debugobj(cxt, " checking %s", ent->name));
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+
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+ /* Note that MS_REC may be used for more flags, so we have to keep
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+ * track about number of recursive options to keep the MS_REC in the
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+ * mountflags if necessary.
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+ */
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+ if (ent->id & MS_REC)
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+ rec_count++;
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+
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+ if (!(ent->id & MS_PROPAGATION))
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continue;
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ad = mnt_new_addmount();
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@@ -96,13 +107,21 @@ static int init_propagation(struct libmnt_context *cxt)
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return -ENOMEM;
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ad->mountflags = ent->id;
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+ DBG(CXT, ul_debugobj(cxt, " adding extra mount(2) call for %s", ent->name));
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rc = mnt_context_append_additional_mount(cxt, ad);
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if (rc)
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return rc;
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+ DBG(CXT, ul_debugobj(cxt, " removing %s from primary mount(2) call", ent->name));
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cxt->mountflags &= ~ent->id;
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+
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+ if (ent->id & MS_REC)
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+ rec_count--;
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}
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+ if (rec_count)
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+ cxt->mountflags |= MS_REC;
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+
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return 0;
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}
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diff --git a/libmount/src/optstr.c b/libmount/src/optstr.c
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index 8248f0dee..cc077ffd9 100644
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--- a/libmount/src/optstr.c
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+++ b/libmount/src/optstr.c
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@@ -800,14 +800,17 @@ int mnt_optstr_apply_flags(char **optstr, unsigned long flags,
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if (rc)
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goto err;
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}
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- if (!(ent->mask & MNT_INVERT))
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+ if (!(ent->mask & MNT_INVERT)) {
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fl &= ~ent->id;
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+ if (ent->id & MS_REC)
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+ fl |= MS_REC;
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+ }
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}
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}
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}
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- /* add missing options */
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- if (fl) {
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+ /* add missing options (but ignore fl if contains MS_REC only) */
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+ if (fl && fl != MS_REC) {
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const struct libmnt_optmap *ent;
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char *p;
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--
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2.31.1
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