[PATCH] ubifs: Add freeze support

Hyunchul Lee
2017-05-25T23:30:46Z

From: Hyunchul Lee <cheol.lee@lge.com>

for un/freeze support, implement freeze_super and un/freeze_fs
of super_operations.
ubifs_freeze_super just calls freeze_super. because freeze_super always
succeeds if file system is read-only, UBIFS errors should be checked.
if there are errors, UBIFS is switched to read-only mode.
ubifs_freeze_fs runs commit if TNC/LPT isn't clean. though all writes
are blocked and sync_fs is called before, if commit alreay was started
before writes are blocked, TNC/LPT might have dirty COW nodes.

Signed-off-by: Hyunchul Lee <cheol.lee@lge.com>
---
fs/ubifs/commit.c | 6 +++---
fs/ubifs/super.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/ubifs/ubifs.h | 1 +
3 files changed, 67 insertions(+), 3 deletions(-)

diff --git a/fs/ubifs/commit.c b/fs/ubifs/commit.c
index 63f5661..ab347ff 100644
--- a/fs/ubifs/commit.c
+++ b/fs/ubifs/commit.c
@@ -49,7 +49,7 @@
#include "ubifs.h"

/*
- * nothing_to_commit - check if there is nothing to commit.
+ * ubifs_nothing_to_commit - check if there is nothing to commit.
* @c: UBIFS file-system description object
*
* This is a helper function which checks if there is anything to commit. It is
@@ -65,7 +65,7 @@
*
* This function returns %1 if there is nothing to commit and %0 otherwise.
*/
-static int nothing_to_commit(struct ubifs_info *c)
+int ubifs_nothing_to_commit(struct ubifs_info *c)
{
/*
* During mounting or remounting from R/O mode to R/W mode we may
@@ -120,7 +120,7 @@ static int do_commit(struct ubifs_info *c)
goto out_up;
}

- if (nothing_to_commit(c)) {
+ if (ubifs_nothing_to_commit(c)) {
up_write(&c->commit_sem);
err = 0;
goto out_cancel;
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index b73811b..16fc22c 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -356,6 +356,7 @@ static void ubifs_evict_inode(struct inode *inode)
if (inode->i_nlink)
goto done;

+ sb_start_intwrite(inode->i_sb);
if (is_bad_inode(inode))
goto out;

@@ -377,6 +378,7 @@ static void ubifs_evict_inode(struct inode *inode)
c->bi.nospace = c->bi.nospace_rp = 0;
smp_wmb();
}
+ sb_end_intwrite(inode->i_sb);
done:
clear_inode(inode);
#ifdef CONFIG_UBIFS_FS_ENCRYPTION
@@ -486,6 +488,64 @@ static int ubifs_sync_fs(struct super_block *sb, int wait)
return ubi_sync(c->vi.ubi_num);
}

+static int ubifs_freeze_super(struct super_block *sb)
+{
+ struct ubifs_info *c = sb->s_fs_info;
+ int err;
+
+ dbg_gen("starting");
+ /* freeze_super always succeeds if file system is in read-only.
+ * however if there are errors, UBIFS is switched to read-only mode.
+ * so @ro_error should be checked.
+ */
+ err = freeze_super(sb);
+ if (!err && c->ro_error) {
+ thaw_super(sb);
+ return -EIO;
+ }
+ return err;
+}
+
+static int ubifs_freeze(struct super_block *sb)
+{
+ struct ubifs_info *c = sb->s_fs_info;
+ int ret;
+
+ if (c->ro_error)
+ return -EIO;
+
+ if (c->ro_mount)
+ return 0;
+
+ down_write(&c->commit_sem);
+ ret = ubifs_nothing_to_commit(c);
+ up_write(&c->commit_sem);
+
+ /* writes were blocked and ubifs_sync_fs was called before.
+ * but TNC/LPT isn't guarranteed to be clean. because if commit was
+ * already started before writes were blocked, TNC/LPT might have
+ * COW nodes. so we try to commit again in this case.
+ */
+ if (!ret) {
+ ret = ubifs_run_commit(c);
+ if (ret)
+ return ret;
+
+ down_write(&c->commit_sem);
+ ret = ubifs_nothing_to_commit(c);
+ up_write(&c->commit_sem);
+ if (!ret)
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int ubifs_unfreeze(struct super_block *sb)
+{
+ return 0;
+}
+
/**
* init_constants_early - initialize UBIFS constants.
* @c: UBIFS file-system description object
@@ -1889,6 +1949,9 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
.remount_fs = ubifs_remount_fs,
.show_options = ubifs_show_options,
.sync_fs = ubifs_sync_fs,
+ .freeze_super = ubifs_freeze_super,
+ .freeze_fs = ubifs_freeze,
+ .unfreeze_fs = ubifs_unfreeze,
};

/**
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index abdd116..545796e 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1645,6 +1645,7 @@ unsigned long ubifs_shrink_count(struct shrinker *shrink,
void ubifs_recovery_commit(struct ubifs_info *c);
int ubifs_gc_should_commit(struct ubifs_info *c);
void ubifs_wait_for_commit(struct ubifs_info *c);
+int ubifs_nothing_to_commit(struct ubifs_info *c);

/* master.c */
int ubifs_read_master(struct ubifs_info *c);
--
1.9.1