Messages in this thread Patch in this message | | | Date | Fri, 1 Aug 2003 15:10:28 +0400 | From | Oleg Drokin <> | Subject | Re: [PATCH] [2.5] reiserfs: fix races between link and unlink on same file |
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Hello!
On Thu, Jul 31, 2003 at 01:37:08PM -0700, Andrew Morton wrote:
> > This patch (originally by Chris Mason) fixes link/unlink races in reiserfs. > Could you describe the race a little more please? Why is the VFS's hold of > i_sem on the parent directory not sufficient?
Well, we do not take i_sem on parent directory of source filename for sys_link, I think. So we might endup in sys_link() with inode that is already deleted/being deleted (and nlink==0). Actually, I naturally thought that only i_nlink check to be non zero at reiserfs_link time should be enough, but Chris is sure that we need entire patch, so may be he may add more comments to that.
BTW, looking at vfs_link, this patch (below the message) seems to be natural thing to do, is not it?
> > + > > + /* > > + * we schedule before doing the add_save_link call, save the link > > + * count so we don't race > This comment would seem to imply lock_kernel()-based locking, but > lock_kernel() is not held here.
It is. This reiserfs_write_lock/unlock stuff are in fact lock_kernel()/unlock_kernel(), only I invented those macroses to easy conversion to more fine-grained locking later. Except that Hans now does not want this to happen.
Bye, Oleg
===== fs/namei.c 1.81 vs edited ===== --- 1.81/fs/namei.c Fri Jul 11 09:23:45 2003 +++ edited/fs/namei.c Fri Aug 1 14:40:29 2003 @@ -1793,17 +1793,17 @@ return -EPERM; if (!dir->i_op || !dir->i_op->link) return -EPERM; - if (S_ISDIR(old_dentry->d_inode->i_mode)) + if (S_ISDIR(inode->i_mode)) return -EPERM; error = security_inode_link(old_dentry, dir, new_dentry); if (error) return error; - down(&old_dentry->d_inode->i_sem); + down(&inode->i_sem); DQUOT_INIT(dir); error = dir->i_op->link(old_dentry, dir, new_dentry); - up(&old_dentry->d_inode->i_sem); + up(&inode->i_sem); if (!error) { inode_dir_notify(dir, DN_CREATE); security_inode_post_link(old_dentry, dir, new_dentry); - 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/
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