From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F805C433B4 for ; Thu, 13 May 2021 20:18:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED4B7613B5 for ; Thu, 13 May 2021 20:18:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232535AbhEMUTZ (ORCPT ); Thu, 13 May 2021 16:19:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:43914 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232513AbhEMUTY (ORCPT ); Thu, 13 May 2021 16:19:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E433E613CB; Thu, 13 May 2021 20:18:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1620937094; bh=W9MrwOqUNvsM8PkLUhR26DHv1FlZ5/cUY1DXnkIrsK8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GQH884ivptZyg9EEY6uVSuJ7Lj2ZiJA4R4KjZMrhvZ/0ZoSI5ze+S/xMhOhH/T+5B Ogww+S8VPebf7JYkUBuG5ZQ+wpor/EMZhxWWl2c4Duob9h8sIrMfOHOdEMuKijzX4j b+MYwdwZnTZaPiNEEgFxuVcA4qipmngxqwT6W5JwFWyNlD9WIjem34/O3SpqRIS0Tz EzGzVOK5DSLsYhIlf/1dU6CFH3i+OcL9FDEN7q32GQKoFZh/Ja+myq3HXhMU5tIPAg S48LKu8a45syeRpp4/8w4pMQoanR1UWww7A00wl4Ya5j781fgoocFxiqldJNT/Ctaz 5vT6usriB9SBQ== Date: Thu, 13 May 2021 13:18:12 -0700 From: "Darrick J. Wong" To: Theodore Ts'o Cc: Leah Rumancik , linux-ext4@vger.kernel.org Subject: Re: [PATCH v4 1/3] ext4: add discard/zeroout flags to journal flush Message-ID: <20210513201812.GA9617@magnolia> References: <20210511180428.3358267-1-leah.rumancik@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu, May 13, 2021 at 02:09:26PM -0400, Theodore Ts'o wrote: > On Tue, May 11, 2021 at 06:04:26PM +0000, Leah Rumancik wrote: > > @@ -3223,7 +3223,7 @@ static sector_t ext4_bmap(struct address_space *mapping, sector_t block) > > ext4_clear_inode_state(inode, EXT4_STATE_JDATA); > > journal = EXT4_JOURNAL(inode); > > jbd2_journal_lock_updates(journal); > > - err = jbd2_journal_flush(journal); > > + err = jbd2_journal_flush(journal, 0); > > In the ocfs2 changes, I noticed you are using "false", instead of 0, > in the second argument to jbd2_journal_flush. > > When I looked more closely, the function signature of > jbd2_journal_flush is also using an unsigned long long for flags, > which struck me as strange: > > > +extern int jbd2_journal_flush(journal_t *journal, unsigned long long flags); > > I then noticed that later in the patch series, the ioctl argument is > taking an unsigned long long and we're passing that straight through > to jbd2_journal_flush(). > > First of all, unsigned long long is not very efficient on many > platforms (especially 32-bit platforms), but also on platforms where > int is 32 bits. If we don't expect us to need more than 32 flag bits, > I'd suggest explicit ly using __u32 in ioctl interface. (__u32 is > fine; it's the use of the base int type which can get us into trouble, > since int can be either 32 or 64 bits depending on the architecture). FWIW I had been advocating for u64 for the ioctl interface since that's the hardest part to change; once we've gotten that into the kernel and remapped the ioctl flags to jbd2 flags, you can do whatever you want. > Secondly, I'd suggest using a different set of flags for > jbd2_journal_flush(), which is an internal kernel interface, and the > EXT4_IOC_CHECKPOINT interface. We might in the future want to add > some internal flags to jbd2_journal_flush that we do *not* want to > expose via EXT4_IOC_CHECKPOINT, and so it's best that we keep those > two interfaces separate. > > > diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c > > index 2dc944442802..f86929dbca3c 100644 > > --- a/fs/jbd2/journal.c > > +++ b/fs/jbd2/journal.c > > @@ -1686,6 +1686,106 @@ static void jbd2_mark_journal_empty(journal_t *journal, int write_op) > > write_unlock(&journal->j_state_lock); > > } > > > > +#define JBD2_ERASE_FLAG_DISCARD 1 > > +#define JBD2_ERASE_FLAG_ZEROOUT 2 > > I'd suggest defining these in include/linux/jbd2.h, and giving them > names like: JBD2_JOURNAL_FLUSH_DISCARD and JBD2_JOURNAL_FLUSH_ERASE... > (and making the flags parameter an unsigned int). > > > + /* flags must be set to either discard or zeroout */ > > + if ((flags & JBD2_ERASE_FLAG_DISCARD & JBD2_ERASE_FLAG_ZEROOUT) || !flags) > > + return -EINVAL; > > The expression (flags & JBD2_ERASE_FLAG_DISCARD & JBD2_ERASE_FLAG_ZEROOUT) > is always going to evaluate to zero, since (1 & 2) is 0. > > What you probably want is something like: > > #define JBD2_JOURNAL_FLUSH_DISCARD 0x0001 > #define JBD2_JOURNAL_FLUSH_ZEROOUT 0x0002 > #define JBD2_JOURNAL_FLUSH_VALID 0x0003 > > if ((flags & ~JBD2_JOURNAL_FLUSH_VALID) || > ((flags & JBD2_JOURNAL_FLUSH_DISCARD) && > (flags & JBD2_JOURNAL_FLUSH_ZEROOUT))) > return -EINVAL; > > > + > > + err = jbd2_journal_bmap(journal, log_offset, &block_start); > > + if (err) { > > + printk(KERN_ERR "JBD2: bad block at offset %lu", log_offset); > > + return err; > > + } > > We could get rid of this, and instead make sure block_start is initialized > to ~((unsigned long long) 0). Then in the loop we can do... Also FWIW I can't find the fiemap code that let you do fiemap from within the kernel, so I guess we only talked about it on fsdevel and none of it ever got merged. So I guess looping is what we'll have to do for now... --D > > + > > + /* > > + * use block_start - 1 to meet check for contiguous with previous region: > > + * phys_block == block_stop + 1 > > + */ > > + block_stop = block_start - 1; > > + > > + for (block = log_offset; block < journal->j_total_len; block++) { > > + err = jbd2_journal_bmap(journal, block, &phys_block); > > + if (err) { > > + printk(KERN_ERR "JBD2: bad block at offset %lu", block); > > + return err; > > + } > > if (block_start == ~((unsigned long long) 0)) { > block_start = phys_block; > block_Stop = block_start - 1; > } > > > + > > + if (block == journal->j_total_len - 1) { > > + block_stop = phys_block; > > + } else if (phys_block == block_stop + 1) { > > + block_stop++; > > + continue; > > + } > > + > > + /* > > + * not contiguous with prior physical block or this is last > > + * block of journal, take care of the region > > + */ > > + byte_start = block_start * journal->j_blocksize; > > + byte_stop = block_stop * journal->j_blocksize; > > + byte_count = (block_stop - block_start + 1) * > > + journal->j_blocksize; > > + > > + truncate_inode_pages_range(journal->j_dev->bd_inode->i_mapping, > > + byte_start, byte_stop); > > + > > + if (flags & JBD2_ERASE_FLAG_DISCARD) { > > + err = blkdev_issue_discard(journal->j_dev, > > + byte_start >> SECTOR_SHIFT, > > + byte_count >> SECTOR_SHIFT, > > + GFP_NOFS, 0); > > + } else if (flags & JBD2_ERASE_FLAG_ZEROOUT) { > > + err = blkdev_issue_zeroout(journal->j_dev, > > + byte_start >> SECTOR_SHIFT, > > + byte_count >> SECTOR_SHIFT, > > + GFP_NOFS, 0); > > + } > > + > > + if (unlikely(err != 0)) { > > + printk(KERN_ERR "JBD2: (error %d) unable to wipe journal at physical blocks %llu - %llu", > > + err, block_start, block_stop); > > + return err; > > + } > > + > > + block_start = phys_block; > > + block_stop = phys_block; > > Is this right? When we initialized the loop, above, block_stop was > set to block_start-1 (where block_start == phys_block). So I think it > might be more correct to replace the above two lines with: > > block_start = ~((unsigned long long) 0); > > ... and then let block_start and block_stop be initialized in a single > place. Do you agree? Does this make sense to you? > > - Ted