On Tue, Sep 25, 2012 at 04:59:21PM -0400, Theodore Ts'o wrote: > On Tue, Sep 25, 2012 at 08:42:52PM +0800, Zheng Liu wrote: > > > If so, we might want to think about adding a sanity check to make sure > > > that by the time we are done with the inode in ext4_evict_inode() > > > (after we have forced writeback), the ext4_es_tree is empty. Agreed? > > > > Today I revise this patch again, and I find extent_status_tree is freed > > in ext4_clear_inode(). So maybe I don't think that we need to check > > this tree to be freed in ext4_evict_inode(). This change is in this > > patch '[RFC][PATCH 4/8 v2] ext4: let ext4 maintain extent status tree'. > > What's your opinion? > > When you say "revise this patch again", does that mean that you would > like to submit a new set of patch series with changes? Or just that > you are looking at this patch set again? > > It's certainly true that ext4_evict_inode() will call > ext4_clear_inode(), so it's not a question of worrying about a memory > leak. I was thinking more about doing this as a cheap sanity check > for the data structure. By the time we call ext4_evict_inode(), the > mm layer all writeback should be complete. Hence, all of the entries > to the tree _should_ have been removed by the time we call > ext4_evict_inode(). > > I don't know if this is going to change as you start using this data > structure for other purposes (such as locking a range of pages), but > if I understand how things are currently working, it _should_ be the > case that when ext4_evict_inode() calls ext4_clear_inode(), the call > to ext4_es_remove_extent() should be a no-op, since all of the nodes > in the extent status tree should have been released by then. If it > isn't, then either I'm not understanding the code, or there's a bug in > the code. Hi Ted, When I try to add a BUG_ON in ext4_evict_inode() to ensure that extent status tree is empty, I will get an error, which reports that the tree is not empty. I find that there still has some dirty pages when we call ext4_evict_inode() because vfs doesn't write all dirty pages back. In iput_final(), we firstly call ext4_drop_inode(). If the return value is true, we won't call write_inode_now() to do a writeback. It means that we write some data to a file and remove it immediately, and then all dirty pages that aren't during writeback progress won't be written. These pages will be truncated in ext4_evict_inode(). Thus, the extent status tree is possible not to be empty when we call ext4_evict_inode(). So we cannot add a sanity check in this function. Am I missing something? Regards, Zheng -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
