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| author | Karel Zak | 2018-06-01 12:16:19 +0200 |
|---|---|---|
| committer | Karel Zak | 2018-06-01 12:16:19 +0200 |
| commit | 816773b475900909d42c2c8282a6ac50252cac22 (patch) | |
| tree | 94a7673aae55f11bc0c28aa16dd393b2e4e1162a /libmount/src/context_mount.c | |
| parent | mount: use internally string to set move/bind operations (diff) | |
| download | kernel-qcow2-util-linux-816773b475900909d42c2c8282a6ac50252cac22.tar.gz kernel-qcow2-util-linux-816773b475900909d42c2c8282a6ac50252cac22.tar.xz kernel-qcow2-util-linux-816773b475900909d42c2c8282a6ac50252cac22.zip | |
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>
Diffstat (limited to 'libmount/src/context_mount.c')
| -rw-r--r-- | libmount/src/context_mount.c | 25 |
1 files changed, 22 insertions, 3 deletions
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; } |