This prevents the lower super_block from being destroyed too early, when a
lower file system is being unmounted with MNT_FORCE or MNT_DETACH.
Signed-off-by: Erez Zadok <ezk@xxxxxxxxxxxxx>
---
fs/unionfs/main.c | 3 +++
fs/unionfs/super.c | 14 ++++++++++++++
fs/unionfs/union.h | 2 +-
3 files changed, 18 insertions(+), 1 deletions(-)
diff --git a/fs/unionfs/main.c b/fs/unionfs/main.c
index 23c18f7..ba3471d 100644
--- a/fs/unionfs/main.c
+++ b/fs/unionfs/main.c
@@ -636,6 +636,7 @@ static int unionfs_read_super(struct super_block *sb, void *raw_data,
sbend(sb) = bend = lower_root_info->bend;
for (bindex = bstart; bindex <= bend; bindex++) {
struct dentry *d = lower_root_info->lower_paths[bindex].dentry;
+ atomic_inc(&d->d_sb->s_active);
unionfs_set_lower_super_idx(sb, bindex, d->d_sb);
}
@@ -711,6 +712,8 @@ out_dput:
dput(d);
/* initializing: can't use unionfs_mntput here */
mntput(m);
+ /* drop refs we took earlier */
+ atomic_dec(&d->d_sb->s_active);
}
kfree(lower_root_info->lower_paths);
kfree(lower_root_info);
diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c
index 986c980..175840f 100644
--- a/fs/unionfs/super.c
+++ b/fs/unionfs/super.c
@@ -116,6 +116,14 @@ static void unionfs_put_super(struct super_block *sb)
}
BUG_ON(leaks != 0);
+ /* decrement lower super references */
+ for (bindex = bstart; bindex <= bend; bindex++) {
+ struct super_block *s;
+ s = unionfs_lower_super_idx(sb, bindex);
+ unionfs_set_lower_super_idx(sb, bindex, NULL);
+ atomic_dec(&s->s_active);
+ }
+
kfree(spd->data);
kfree(spd);
sb->s_fs_info = NULL;
@@ -729,6 +737,12 @@ out_no_change:
*/
purge_sb_data(sb);
+ /* grab new lower super references; release old ones */
+ for (i = 0; i < new_branches; i++)
+ atomic_inc(&new_data[i].sb->s_active);
+ for (i = 0; i < new_branches; i++)
+ atomic_dec(&UNIONFS_SB(sb)->data[i].sb->s_active);
+
/* copy new vectors into their correct place */
tmp_data = UNIONFS_SB(sb)->data;
UNIONFS_SB(sb)->data = new_data;
diff --git a/fs/unionfs/union.h b/fs/unionfs/union.h
index 4b4d6c9..786c4be 100644
--- a/fs/unionfs/union.h
+++ b/fs/unionfs/union.h
@@ -127,7 +127,7 @@ struct unionfs_dentry_info {
/* These are the pointers to our various objects. */
struct unionfs_data {
- struct super_block *sb;
+ struct super_block *sb; /* lower super_block */
atomic_t open_files; /* number of open files on branch */
int branchperms;
int branch_id; /* unique branch ID at re/mount time */
--
1.5.2.2
-
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