nilfs2: do not allocate multiple super block instances for a device
This stops allocating multiple super block instances for a device.
All snapshots and a current mode mount (i.e. latest tree) will be
controlled with nilfs_root objects that are kept within an sb
instance.
nilfs_get_sb() is rewritten so that it always has a root object for
the latest tree and snapshots make additional root objects.
The root dentry of the latest tree is binded to sb->s_root even if it
isn't attached on a directory. Root dentries of snapshots or the
latest tree are binded to mnt->mnt_root on which they are mounted.
With this patch, nilfs_find_sbinfo() function, nilfs->ns_supers list,
and nilfs->ns_current back pointer, are deleted. In addition,
init_nilfs() and load_nilfs() are simplified since they will be called
once for a device, not repeatedly called for mount points.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index ebeb746..2e58e7c 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -355,16 +355,11 @@
nilfs_cleanup_super(sbi);
up_write(&nilfs->ns_sem);
}
- down_write(&nilfs->ns_super_sem);
- if (nilfs->ns_current == sbi)
- nilfs->ns_current = NULL;
- list_del_init(&sbi->s_list);
- up_write(&nilfs->ns_super_sem);
put_nilfs(sbi->s_nilfs);
sbi->s_super = NULL;
sb->s_fs_info = NULL;
- nilfs_put_sbinfo(sbi);
+ kfree(sbi);
}
static int nilfs_sync_fs(struct super_block *sb, int wait)
@@ -500,12 +495,12 @@
{
struct super_block *sb = vfs->mnt_sb;
struct nilfs_sb_info *sbi = NILFS_SB(sb);
+ struct nilfs_root *root = NILFS_I(vfs->mnt_root->d_inode)->i_root;
if (!nilfs_test_opt(sbi, BARRIER))
seq_puts(seq, ",nobarrier");
- if (nilfs_test_opt(sbi, SNAPSHOT))
- seq_printf(seq, ",cp=%llu",
- (unsigned long long int)sbi->s_snapshot_cno);
+ if (root->cno != NILFS_CPTREE_CURRENT_CNO)
+ seq_printf(seq, ",cp=%llu", (unsigned long long)root->cno);
if (nilfs_test_opt(sbi, ERRORS_PANIC))
seq_puts(seq, ",errors=panic");
if (nilfs_test_opt(sbi, ERRORS_CONT))
@@ -605,27 +600,11 @@
if (match_int(&args[0], &option) || option <= 0)
return 0;
if (is_remount) {
- if (!nilfs_test_opt(sbi, SNAPSHOT)) {
- printk(KERN_ERR
- "NILFS: cannot change regular "
- "mount to snapshot.\n");
- return 0;
- } else if (option != sbi->s_snapshot_cno) {
- printk(KERN_ERR
- "NILFS: cannot remount to a "
- "different snapshot.\n");
- return 0;
- }
- break;
- }
- if (!(sb->s_flags & MS_RDONLY)) {
- printk(KERN_ERR "NILFS: cannot mount snapshot "
- "read/write. A read-only option is "
- "required.\n");
+ printk(KERN_ERR
+ "NILFS: \"%s\" option is invalid "
+ "for remount.\n", p);
return 0;
}
- sbi->s_snapshot_cno = option;
- nilfs_set_opt(sbi, SNAPSHOT);
break;
case Opt_norecovery:
nilfs_set_opt(sbi, NORECOVERY);
@@ -771,16 +750,32 @@
goto out;
}
- dentry = d_alloc_root(inode);
- if (!dentry) {
- iput(inode);
- printk(KERN_ERR "NILFS: get root dentry failed\n");
- ret = -ENOMEM;
- goto out;
+ if (root->cno == NILFS_CPTREE_CURRENT_CNO) {
+ dentry = d_find_alias(inode);
+ if (!dentry) {
+ dentry = d_alloc_root(inode);
+ if (!dentry) {
+ iput(inode);
+ ret = -ENOMEM;
+ goto failed_dentry;
+ }
+ } else {
+ iput(inode);
+ }
+ } else {
+ dentry = d_obtain_alias(inode);
+ if (IS_ERR(dentry)) {
+ ret = PTR_ERR(dentry);
+ goto failed_dentry;
+ }
}
*root_dentry = dentry;
out:
return ret;
+
+ failed_dentry:
+ printk(KERN_ERR "NILFS: get root dentry failed\n");
+ goto out;
}
static int nilfs_attach_snapshot(struct super_block *s, __u64 cno,
@@ -817,6 +812,25 @@
return ret;
}
+static int nilfs_tree_was_touched(struct dentry *root_dentry)
+{
+ return atomic_read(&root_dentry->d_count) > 1;
+}
+
+/**
+ * nilfs_try_to_shrink_tree() - try to shrink dentries of a checkpoint
+ * @root_dentry: root dentry of the tree to be shrunk
+ *
+ * This function returns true if the tree was in-use.
+ */
+static int nilfs_try_to_shrink_tree(struct dentry *root_dentry)
+{
+ if (have_submounts(root_dentry))
+ return true;
+ shrink_dcache_parent(root_dentry);
+ return nilfs_tree_was_touched(root_dentry);
+}
+
/**
* nilfs_fill_super() - initialize a super block instance
* @sb: super_block
@@ -845,7 +859,6 @@
get_nilfs(nilfs);
sbi->s_nilfs = nilfs;
sbi->s_super = sb;
- atomic_set(&sbi->s_count, 1);
err = init_nilfs(nilfs, sbi, (char *)data);
if (err)
@@ -853,7 +866,6 @@
spin_lock_init(&sbi->s_inode_lock);
INIT_LIST_HEAD(&sbi->s_dirty_files);
- INIT_LIST_HEAD(&sbi->s_list);
/*
* Following initialization is overlapped because
@@ -875,20 +887,11 @@
if (err)
goto failed_sbi;
- if (nilfs_test_opt(sbi, SNAPSHOT)) {
- err = nilfs_attach_snapshot(sb, sbi->s_snapshot_cno,
- &sb->s_root);
- if (err)
- goto failed_sbi;
-
- goto add_to_supers;
- }
-
cno = nilfs_last_cno(nilfs);
err = nilfs_attach_checkpoint(sbi, cno, true, &fsroot);
if (err) {
- printk(KERN_ERR "NILFS: error loading a checkpoint"
- " (checkpoint number=%llu).\n", (unsigned long long)cno);
+ printk(KERN_ERR "NILFS: error loading last checkpoint "
+ "(checkpoint number=%llu).\n", (unsigned long long)cno);
goto failed_sbi;
}
@@ -910,13 +913,6 @@
up_write(&nilfs->ns_sem);
}
- add_to_supers:
- down_write(&nilfs->ns_super_sem);
- list_add(&sbi->s_list, &nilfs->ns_supers);
- if (!nilfs_test_opt(sbi, SNAPSHOT))
- nilfs->ns_current = sbi;
- up_write(&nilfs->ns_super_sem);
-
return 0;
failed_segctor:
@@ -928,7 +924,7 @@
failed_sbi:
put_nilfs(nilfs);
sb->s_fs_info = NULL;
- nilfs_put_sbinfo(sbi);
+ kfree(sbi);
return err;
}
@@ -938,13 +934,10 @@
struct the_nilfs *nilfs = sbi->s_nilfs;
unsigned long old_sb_flags;
struct nilfs_mount_options old_opts;
- int was_snapshot, err;
+ int err;
- down_write(&nilfs->ns_super_sem);
old_sb_flags = sb->s_flags;
old_opts.mount_opt = sbi->s_mount_opt;
- old_opts.snapshot_cno = sbi->s_snapshot_cno;
- was_snapshot = nilfs_test_opt(sbi, SNAPSHOT);
if (!parse_options(data, sb, 1)) {
err = -EINVAL;
@@ -953,11 +946,6 @@
sb->s_flags = (sb->s_flags & ~MS_POSIXACL);
err = -EINVAL;
- if (was_snapshot && !(*flags & MS_RDONLY)) {
- printk(KERN_ERR "NILFS (device %s): cannot remount snapshot "
- "read/write.\n", sb->s_id);
- goto restore_opts;
- }
if (!nilfs_valid_fs(nilfs)) {
printk(KERN_WARNING "NILFS (device %s): couldn't "
@@ -1014,14 +1002,11 @@
up_write(&nilfs->ns_sem);
}
out:
- up_write(&nilfs->ns_super_sem);
return 0;
restore_opts:
sb->s_flags = old_sb_flags;
sbi->s_mount_opt = old_opts.mount_opt;
- sbi->s_snapshot_cno = old_opts.snapshot_cno;
- up_write(&nilfs->ns_super_sem);
return err;
}
@@ -1075,18 +1060,14 @@
static int nilfs_set_bdev_super(struct super_block *s, void *data)
{
- struct nilfs_super_data *sd = data;
-
- s->s_bdev = sd->bdev;
+ s->s_bdev = data;
s->s_dev = s->s_bdev->bd_dev;
return 0;
}
static int nilfs_test_bdev_super(struct super_block *s, void *data)
{
- struct nilfs_super_data *sd = data;
-
- return sd->sbi && s->s_fs_info == (void *)sd->sbi;
+ return (void *)s->s_bdev == data;
}
static int
@@ -1097,7 +1078,8 @@
struct super_block *s;
fmode_t mode = FMODE_READ;
struct the_nilfs *nilfs;
- int err, need_to_close = 1;
+ struct dentry *root_dentry;
+ int err, s_new = false;
if (!(flags & MS_RDONLY))
mode |= FMODE_WRITE;
@@ -1106,12 +1088,6 @@
if (IS_ERR(sd.bdev))
return PTR_ERR(sd.bdev);
- /*
- * To get mount instance using sget() vfs-routine, NILFS needs
- * much more information than normal filesystems to identify mount
- * instance. For snapshot mounts, not only a mount type (ro-mount
- * or rw-mount) but also a checkpoint number is required.
- */
sd.cno = 0;
sd.flags = flags;
if (nilfs_identify((char *)data, &sd)) {
@@ -1127,38 +1103,7 @@
mutex_lock(&nilfs->ns_mount_mutex);
- if (!sd.cno) {
- /*
- * Check if an exclusive mount exists or not.
- * Snapshot mounts coexist with a current mount
- * (i.e. rw-mount or ro-mount), whereas rw-mount and
- * ro-mount are mutually exclusive.
- */
- down_read(&nilfs->ns_super_sem);
- if (nilfs->ns_current &&
- ((nilfs->ns_current->s_super->s_flags ^ flags)
- & MS_RDONLY)) {
- up_read(&nilfs->ns_super_sem);
- err = -EBUSY;
- goto failed_unlock;
- }
- up_read(&nilfs->ns_super_sem);
- }
-
- /*
- * Find existing nilfs_sb_info struct
- */
- sd.sbi = nilfs_find_sbinfo(nilfs, !(flags & MS_RDONLY), sd.cno);
-
- /*
- * Get super block instance holding the nilfs_sb_info struct.
- * A new instance is allocated if no existing mount is present or
- * existing instance has been unmounted.
- */
- s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, &sd);
- if (sd.sbi)
- nilfs_put_sbinfo(sd.sbi);
-
+ s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, sd.bdev);
if (IS_ERR(s)) {
err = PTR_ERR(s);
goto failed_unlock;
@@ -1167,6 +1112,8 @@
if (!s->s_root) {
char b[BDEVNAME_SIZE];
+ s_new = true;
+
/* New superblock instance created */
s->s_flags = flags;
s->s_mode = mode;
@@ -1179,16 +1126,53 @@
goto cancel_new;
s->s_flags |= MS_ACTIVE;
- need_to_close = 0;
+ } else if (!sd.cno) {
+ int busy = false;
+
+ if (nilfs_tree_was_touched(s->s_root)) {
+ busy = nilfs_try_to_shrink_tree(s->s_root);
+ if (busy && (flags ^ s->s_flags) & MS_RDONLY) {
+ printk(KERN_ERR "NILFS: the device already "
+ "has a %s mount.\n",
+ (s->s_flags & MS_RDONLY) ?
+ "read-only" : "read/write");
+ err = -EBUSY;
+ goto failed_super;
+ }
+ }
+ if (!busy) {
+ /*
+ * Try remount to setup mount states if the current
+ * tree is not mounted and only snapshots use this sb.
+ */
+ err = nilfs_remount(s, &flags, data);
+ if (err)
+ goto failed_super;
+ }
+ }
+
+ if (sd.cno) {
+ err = nilfs_attach_snapshot(s, sd.cno, &root_dentry);
+ if (err) {
+ if (s_new)
+ goto cancel_new;
+ goto failed_super;
+ }
+ } else {
+ root_dentry = dget(s->s_root);
}
mutex_unlock(&nilfs->ns_mount_mutex);
put_nilfs(nilfs);
- if (need_to_close)
+ if (!s_new)
close_bdev_exclusive(sd.bdev, mode);
- simple_set_mnt(mnt, s);
+
+ mnt->mnt_sb = s;
+ mnt->mnt_root = root_dentry;
return 0;
+ failed_super:
+ deactivate_locked_super(s);
failed_unlock:
mutex_unlock(&nilfs->ns_mount_mutex);
put_nilfs(nilfs);
@@ -1202,7 +1186,7 @@
put_nilfs(nilfs);
deactivate_locked_super(s);
/*
- * deactivate_locked_super() invokes close_bdev_exclusive().
+ * This deactivate_locked_super() invokes close_bdev_exclusive().
* We must finish all post-cleaning before this call;
* put_nilfs() needs the block device.
*/