Introduce white-out support to tmpfs. Signed-off-by: Jan Blunck --- include/linux/shmem_fs.h | 1 mm/shmem.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 55 insertions(+) --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -33,6 +33,7 @@ struct shmem_sb_info { int policy; /* Default NUMA memory alloc policy */ nodemask_t policy_nodes; /* nodemask for preferred and bind */ spinlock_t stat_lock; + struct inode *whiteout_inode; }; static inline struct shmem_inode_info *SHMEM_I(struct inode *inode) --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1784,6 +1784,42 @@ static int shmem_create(struct inode *di } /* + * This is the whiteout support for tmpfs. It uses one singleton whiteout + * inode per superblock thus it is very similar to shmem_link(). + */ +static int shmem_whiteout(struct inode *dir, struct dentry *dentry) +{ + struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb); + struct inode *inode = sbinfo->whiteout_inode; + + if (!(dir->i_sb->s_flags & MS_WHITEOUT)) + return -EPERM; + + /* + * No ordinary (disk based) filesystem counts whiteouts as inodes; + * but each new link needs a new dentry, pinning lowmem, and + * tmpfs dentries cannot be pruned until they are unlinked. + */ + if (sbinfo->max_inodes) { + spin_lock(&sbinfo->stat_lock); + if (!sbinfo->free_inodes) { + spin_unlock(&sbinfo->stat_lock); + return -ENOSPC; + } + sbinfo->free_inodes--; + spin_unlock(&sbinfo->stat_lock); + } + + dir->i_size += BOGO_DIRENT_SIZE; + inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; + inc_nlink(inode); + atomic_inc(&inode->i_count); /* New dentry reference */ + dget(dentry); /* Extra pinning count for the created dentry */ + d_instantiate(dentry, inode); + return 0; +} + +/* * Link a file.. */ static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry) @@ -2231,6 +2267,9 @@ out: static void shmem_put_super(struct super_block *sb) { + struct shmem_sb_info *sbinfo = sb->s_fs_info; + + iput(sbinfo->whiteout_inode); kfree(sb->s_fs_info); sb->s_fs_info = NULL; } @@ -2305,6 +2344,19 @@ static int shmem_fill_super(struct super if (!root) goto failed_iput; sb->s_root = root; + +#ifdef CONFIG_TMPFS + if (!(sb->s_flags & MS_NOUSER)) { + inode = shmem_get_inode(sb, S_IRUGO | S_IWUGO | S_IFWHT, 0); + if (!inode) { + dput(root); + goto failed; + } + sbinfo->whiteout_inode = inode; + sb->s_flags |= MS_WHITEOUT; + } +#endif + return 0; failed_iput: @@ -2410,6 +2462,7 @@ static const struct inode_operations shm .rmdir = shmem_rmdir, .mknod = shmem_mknod, .rename = shmem_rename, + .whiteout = shmem_whiteout, #endif #ifdef CONFIG_TMPFS_POSIX_ACL .setattr = shmem_notify_change, @@ -2464,6 +2517,7 @@ static struct file_system_type tmpfs_fs_ .name = "tmpfs", .get_sb = shmem_get_sb, .kill_sb = kill_litter_super, + .fs_flags = FS_WHT, }; static struct vfsmount *shm_mnt; -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/