vfs_stat 函数跟踪

本文使用内核源码版本为：2.6.32

vfs_stat函数原型：int vfs_stat(char __user *name, struct kstat *stat)

struct kstat定义位于：include/fs.h

struct kstat {
    u64     ino;
    dev_t       dev;
    umode_t     mode;
    unsigned int    nlink;
    uid_t       uid;
    gid_t       gid;
    dev_t       rdev;
    loff_t      size;
    struct timespec  atime;
    struct timespec mtime;
    struct timespec ctime;
    unsigned long   blksize;
    unsigned long long  blocks;
};

该结构体封装了文件的基本属性

函数 vfs_stat 定义位于：fs/stat.c

int vfs_stat(char __user *name, struct kstat *stat)
{
    return vfs_fstatat(AT_FDCWD, name, stat, 0);    //调用了vfs_fstatat
}
EXPORT_SYMBOL(vfs_stat);

函数 vfs_fstatat 定义于相同文件中

int vfs_fstatat(int dfd, char __user *filename, struct kstat *stat, int flag)
{
    struct path path;
    int error = -EINVAL;
    int lookup_flags = 0;

    if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0)
        goto out;

    if (!(flag & AT_SYMLINK_NOFOLLOW))
        lookup_flags |= LOOKUP_FOLLOW;

    error = user_path_at(dfd, filename, lookup_flags, &path);
    if (error)
        goto out;

    error = vfs_getattr(path.mnt, path.dentry, stat);  //这里调用 vfs_getattr 获取文件属性
    path_put(&path);
out:
    return error;
}
EXPORT_SYMBOL(vfs_fstatat);

函数 vfs_getattr 定义于相同文件中

int vfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
    struct inode *inode = dentry->d_inode;
    int retval;

    retval = security_inode_getattr(mnt, dentry);
    if (retval)
        return retval;

    if (inode->i_op->getattr)
        return inode->i_op->getattr(mnt, dentry, stat);  //通过 inode 取得文件属性

    generic_fillattr(inode, stat);
    return 0;
}
EXPORT_SYMBOL(vfs_getattr);