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VFS: change 'last_dir' to match locking assumption

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new_node makes the assumption that when it does last_dir on a path, a
successive advance would not yield a lock on a vmnt, because last_dir
already locked the vmnt. This is true except when last_dir resolves
to a directory on the parent vmnt of the file that was the result of
advance. For example,
 # cd /
 # echo foo > home
where home is on a different (sub) partition than / is (default
install). last_dir would resolve to / and advance would resolve to
/home.

With this change, last_dir resolves to the root node on the /home
partition, making the assumption valid again.
This commit is contained in:
Thomas Veerman 2012-11-20 13:14:31 +00:00
parent d67db9b39c
commit de83b2a9d9
2 changed files with 39 additions and 2 deletions
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2
servers/vfs/open.c
View file

@ -444,9 +444,9 @@ static struct vnode *new_node(struct lookup *resolve, int oflags, mode_t bits)
else
err_code = r;
unlock_vmnt(dir_vmp);
unlock_vnode(dirp);
unlock_vnode(vp);
unlock_vmnt(dir_vmp);
put_vnode(dirp);
return(NULL);
}

39
servers/vfs/path.c
View file

@ -264,7 +264,9 @@ struct fproc *rfp;
symlink.l_vmnt_lock = VMNT_READ;
sym_vp = advance(res_vp, &symlink, rfp);
if (sym_vp != NULL && S_ISLNK(sym_vp->v_mode)) {
if (sym_vp == NULL) break;
if (S_ISLNK(sym_vp->v_mode)) {
/* Last component is a symlink, but if we've been asked to not
* resolve it, return now.
*/
@ -310,6 +312,41 @@ struct fproc *rfp;
continue;
}
} else {
symloop = 0; /* Not a symlink, so restart counting */
/* If we're crossing a mount point, return root node of mount
* point on which the file resides. That's the 'real' last
* dir that holds the file we're looking for.
*/
if (sym_vp->v_fs_e != res_vp->v_fs_e) {
assert(sym_vmp != NULL);
/* Unlock final file, it might have wrong lock types */
unlock_vnode(sym_vp);
unlock_vmnt(sym_vmp);
put_vnode(sym_vp);
sym_vp = NULL;
/* Also unlock and release erroneous result */
unlock_vnode(*resolve->l_vnode);
unlock_vmnt(*resolve->l_vmp);
put_vnode(res_vp);
/* Relock vmnt and vnode with correct lock types */
lock_vmnt(sym_vmp, resolve->l_vmnt_lock);
lock_vnode(sym_vmp->m_root_node, resolve->l_vnode_lock);
res_vp = sym_vmp->m_root_node;
dup_vnode(res_vp);
*resolve->l_vnode = res_vp;
*resolve->l_vmp = sym_vmp;
/* We've effectively resolved the final component, so
* change it to current directory to prevent future
* 'advances' of returning erroneous results.
*/
strlcpy(dir_entry, ".", NAME_MAX+1);
}
}
break;
} while (symloop < SYMLOOP_MAX);