>From 5dce7adb0c281612a14fa3dd8c8d5ef3f5eb3666 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 7 Feb 2012 22:59:06 +0100 Subject: [PATCH 1/2] vfs: Provide function to get superblock and wait for it to thaw In quota code we need to find a superblock corresponding to a device and wait for superblock to be unfrozen. However this waiting has to happen without s_umount semaphore because that is required for superblock to thaw. So provide a function in VFS for this to keep dances with s_umount where they belong. Signed-off-by: Jan Kara --- fs/super.c | 47 +++++++++++++++++++++++++++++++++++------------ include/linux/fs.h | 1 + 2 files changed, 36 insertions(+), 12 deletions(-) diff --git a/fs/super.c b/fs/super.c index 6015c02..e15aaa9 100644 --- a/fs/super.c +++ b/fs/super.c @@ -593,15 +593,7 @@ void iterate_supers_type(struct file_system_type *type, EXPORT_SYMBOL(iterate_supers_type); -/** - * get_super - get the superblock of a device - * @bdev: device to get the superblock for - * - * Scans the superblock list and finds the superblock of the file system - * mounted on the device given. %NULL is returned if no match is found. - */ - -struct super_block *get_super(struct block_device *bdev) +static struct super_block *__get_super(struct block_device *bdev, bool thawed) { struct super_block *sb; @@ -618,9 +610,13 @@ rescan: spin_unlock(&sb_lock); down_read(&sb->s_umount); /* still alive? */ - if (sb->s_root && (sb->s_flags & MS_BORN)) - return sb; - up_read(&sb->s_umount); + if (sb->s_root && (sb->s_flags & MS_BORN)) { + if (!thawed || sb->s_frozen == SB_UNFROZEN) + return sb; + up_read(&sb->s_umount); + vfs_check_frozen(sb, SB_FREEZE_WRITE); + } else + up_read(&sb->s_umount); /* nope, got unmounted */ spin_lock(&sb_lock); __put_super(sb); @@ -631,9 +627,36 @@ rescan: return NULL; } +/** + * get_super - get the superblock of a device + * @bdev: device to get the superblock for + * + * Scans the superblock list and finds the superblock of the file system + * mounted on the device given. %NULL is returned if no match is found. + */ + +struct super_block *get_super(struct block_device *bdev) +{ + return __get_super(bdev, false); +} EXPORT_SYMBOL(get_super); /** + * get_super_thawed - get thawed superblock of a device + * @bdev: device to get the superblock for + * + * Scans the superblock list and finds the superblock of the file system + * mounted on the device given once the superblock is thawed. %NULL is + * returned if no match is found. + */ + +struct super_block *get_super_thawed(struct block_device *bdev) +{ + return __get_super(bdev, true); +} +EXPORT_SYMBOL(get_super_thawed); + +/** * get_active_super - get an active reference to the superblock of a device * @bdev: device to get the superblock for * diff --git a/include/linux/fs.h b/include/linux/fs.h index 386da09..69cd5bb 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2496,6 +2496,7 @@ extern void get_filesystem(struct file_system_type *fs); extern void put_filesystem(struct file_system_type *fs); extern struct file_system_type *get_fs_type(const char *name); extern struct super_block *get_super(struct block_device *); +extern struct super_block *get_super_thawed(struct block_device *); extern struct super_block *get_active_super(struct block_device *bdev); extern void drop_super(struct super_block *sb); extern void iterate_supers(void (*)(struct super_block *, void *), void *); -- 1.7.1