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nilfs2: get rid of sget use for checking if current mount is present

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This stops using sget() for checking if an r/w-mount or an r/o-mount
exists on the device.  This elimination uses a back pointer to the
current mount added to nilfs object.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Ryusuke Konishi 2009-06-08 01:39:30 +09:00 committed by Al Viro
parent 33c8e57c86
commit 3f82ff5516
2 changed files with 35 additions and 60 deletions
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92
fs/nilfs2/super.c
View File

@ -67,8 +67,6 @@ MODULE_LICENSE("GPL");
static void nilfs_write_super(struct super_block *sb);
static int nilfs_remount(struct super_block *sb, int *flags, char *data);
static int test_exclusive_mount(struct file_system_type *fs_type,
struct block_device *bdev, int flags);
/**
* nilfs_error() - report failure condition on a filesystem
@ -329,6 +327,10 @@ static void nilfs_put_super(struct super_block *sb)
nilfs_commit_super(sbi, 1);
up_write(&nilfs->ns_sem);
}
down_write(&nilfs->ns_sem);
if (nilfs->ns_current == sbi)
nilfs->ns_current = NULL;
up_write(&nilfs->ns_sem);
nilfs_detach_checkpoint(sbi);
put_nilfs(sbi->s_nilfs);
@ -880,6 +882,11 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
goto failed_root;
}
down_write(&nilfs->ns_sem);
if (!nilfs_test_opt(sbi, SNAPSHOT))
nilfs->ns_current = sbi;
up_write(&nilfs->ns_sem);
return 0;
failed_root:
@ -958,14 +965,16 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
* by fsck since we originally mounted the partition.)
*/
down(&sb->s_bdev->bd_mount_sem);
/* Check existing RW-mount */
if (test_exclusive_mount(sb->s_type, sb->s_bdev, 0)) {
down_read(&nilfs->ns_sem);
if (nilfs->ns_current && nilfs->ns_current != sbi) {
printk(KERN_WARNING "NILFS (device %s): couldn't "
"remount because a RW-mount exists.\n",
"remount because an RW-mount exists.\n",
sb->s_id);
up_read(&nilfs->ns_sem);
err = -EBUSY;
goto rw_remount_failed;
}
up_read(&nilfs->ns_sem);
if (sbi->s_snapshot_cno != nilfs_last_cno(nilfs)) {
printk(KERN_WARNING "NILFS (device %s): couldn't "
"remount because the current RO-mount is not "
@ -984,6 +993,7 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
down_write(&nilfs->ns_sem);
nilfs_setup_super(sbi);
nilfs->ns_current = sbi;
up_write(&nilfs->ns_sem);
up(&sb->s_bdev->bd_mount_sem);
@ -1118,10 +1128,23 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
}
down(&sd.bdev->bd_mount_sem);
if (!sd.cno &&
(err = test_exclusive_mount(fs_type, sd.bdev, flags ^ MS_RDONLY))) {
err = (err < 0) ? : -EBUSY;
goto failed_unlock;
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_sem);
if (nilfs->ns_current &&
((nilfs->ns_current->s_super->s_flags ^ flags)
& MS_RDONLY)) {
up_read(&nilfs->ns_sem);
err = -EBUSY;
goto failed_unlock;
}
up_read(&nilfs->ns_sem);
}
/*
@ -1182,57 +1205,6 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
return err;
}
static int nilfs_test_bdev_super3(struct super_block *s, void *data)
{
struct nilfs_super_data *sd = data;
int ret;
if (s->s_bdev != sd->bdev)
return 0;
if (down_read_trylock(&s->s_umount)) {
ret = (s->s_flags & MS_RDONLY) && s->s_root &&
nilfs_test_opt(NILFS_SB(s), SNAPSHOT);
up_read(&s->s_umount);
if (ret)
return 0; /* ignore snapshot mounts */
}
return !((sd->flags ^ s->s_flags) & MS_RDONLY);
}
static int __false_bdev_super(struct super_block *s, void *data)
{
#if 0 /* XXX: workaround for lock debug. This is not good idea */
up_write(&s->s_umount);
#endif
return -EFAULT;
}
/**
* test_exclusive_mount - check whether an exclusive RW/RO mount exists or not.
* fs_type: filesystem type
* bdev: block device
* flag: 0 (check rw-mount) or MS_RDONLY (check ro-mount)
* res: pointer to an integer to store result
*
* This function must be called within a section protected by bd_mount_mutex.
*/
static int test_exclusive_mount(struct file_system_type *fs_type,
struct block_device *bdev, int flags)
{
struct super_block *s;
struct nilfs_super_data sd = { .flags = flags, .bdev = bdev };
s = sget(fs_type, nilfs_test_bdev_super3, __false_bdev_super, &sd);
if (IS_ERR(s)) {
if (PTR_ERR(s) != -EFAULT)
return PTR_ERR(s);
return 0; /* Not found */
}
up_write(&s->s_umount);
deactivate_super(s);
return 1; /* Found */
}
struct file_system_type nilfs_fs_type = {
.owner = THIS_MODULE,
.name = "nilfs2",

3
fs/nilfs2/the_nilfs.h
View File

@ -50,6 +50,7 @@ enum {
* @ns_sem: semaphore for shared states
* @ns_writer_mutex: mutex protecting ns_writer attach/detach
* @ns_writer_refcount: number of referrers on ns_writer
* @ns_current: back pointer to current mount
* @ns_sbh: buffer heads of on-disk super blocks
* @ns_sbp: pointers to super block data
* @ns_sbwtime: previous write time of super blocks
@ -98,6 +99,8 @@ struct the_nilfs {
struct mutex ns_writer_mutex;
atomic_t ns_writer_refcount;
struct nilfs_sb_info *ns_current;
/*
* used for
* - loading the latest checkpoint exclusively.