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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 5F67AC433ED for ; Thu, 13 May 2021 18:09:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 300A96101B for ; Thu, 13 May 2021 18:09:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231462AbhEMSKp (ORCPT ); Thu, 13 May 2021 14:10:45 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:34832 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S231378AbhEMSKl (ORCPT ); Thu, 13 May 2021 14:10:41 -0400 Received: from cwcc.thunk.org (pool-72-74-133-215.bstnma.fios.verizon.net [72.74.133.215]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 14DI9Rr3029289 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 13 May 2021 14:09:27 -0400 Received: by cwcc.thunk.org (Postfix, from userid 15806) id EC33515C3C45; Thu, 13 May 2021 14:09:26 -0400 (EDT) Date: Thu, 13 May 2021 14:09:26 -0400 From: "Theodore Ts'o" To: Leah Rumancik Cc: linux-ext4@vger.kernel.org Subject: Re: [PATCH v4 1/3] ext4: add discard/zeroout flags to journal flush Message-ID: 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: <20210511180428.3358267-1-leah.rumancik@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org 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). 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... > + > + /* > + * 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