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=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 0C8ECC433B4 for ; Thu, 13 May 2021 20:27:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BEFB8613BD for ; Thu, 13 May 2021 20:27:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232860AbhEMU2h (ORCPT ); Thu, 13 May 2021 16:28:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232845AbhEMU2g (ORCPT ); Thu, 13 May 2021 16:28:36 -0400 Received: from mail-qk1-x72c.google.com (mail-qk1-x72c.google.com [IPv6:2607:f8b0:4864:20::72c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F3C8C061574 for ; Thu, 13 May 2021 13:27:26 -0700 (PDT) Received: by mail-qk1-x72c.google.com with SMTP id 76so26783490qkn.13 for ; Thu, 13 May 2021 13:27:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=/S8+aAfgl/yImqy9yxRRCpay02xe0BIIIa9gQvM5ZVw=; b=VJa2VjcwBmSQ4HllLNKZdWjtyBHsgn0ChHYPycOf6JBHtk/gm6sFW2jW7agbEy0/yM UhKB89e1JV1DhdoMkau+2BqU8LCn96jflA/lLSpzVOm9NTzuO4DGQOzP4kUor3r9Rja7 4xHKcRPwAHNowRMu4V0EWnpyi8/4MXrhnb+1Lsay+nckJJraRhyskQ6EqQ/elvkHawAy qxuSyqI5h+r6JiObB4yvhOYUXAG3H9fcMDIFs1shv03+xXF3vgKU/GdKNEuxyAXIW7pg dwitHZj+3L08z6GUWukrsIpwCf6Bev0nKosj7vRPZi5v7vAdocJCPa+pXOQafa6ha/fk cUXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=/S8+aAfgl/yImqy9yxRRCpay02xe0BIIIa9gQvM5ZVw=; b=C4N7+Xq031VdcfLSuMgZrTni/7kmbvEYj0I/xu3qNjesHsf3rfxsetb+e2Ht7SD+Bf O01obfi5zwiFyahrJmWrMdbykmfH8Ax1dyq9b6af8tUCSjqCq3Mw7k2Gg9hFfopUXyB3 J0yWylsyQM6Eo7Ww+aQMC9hLjpt7uvaxLRiv/02o2Blr0MkXI5zklMyIs6Ya2HRiKKQN nfQcxeq7zXKjrwduJENk1ReRT8skQlsrYrlNLZ1AjmaK9Ne80xWkNcfqN+N4JA4nPv2x FocBDFfCVYMYHMm75PAVoek14EGKAyqPHOXx/6VG352EPlBFzt8buE3FgXZUfJNHf104 n+0w== X-Gm-Message-State: AOAM532mJZp1rfd09h9NM43nx8V9AI6Hxngljfvawti1285CjDR2idA6 5tPVChwbfouSFVJbqwf7lNLfbdRGOm9yyA== X-Google-Smtp-Source: ABdhPJxeboZoTBfVE4omeZrl0K5ehpF4C9oKkMQBXu2m9OoROqTF025EXgL/JGTDYzYZeja+lCSoqw== X-Received: by 2002:a37:5ca:: with SMTP id 193mr39739856qkf.356.1620937645325; Thu, 13 May 2021 13:27:25 -0700 (PDT) Received: from google.com ([2601:4c3:201:ed00:8626:664b:8242:8ae7]) by smtp.gmail.com with ESMTPSA id s5sm3297865qkg.88.2021.05.13.13.27.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 May 2021 13:27:25 -0700 (PDT) Date: Thu, 13 May 2021 16:27:23 -0400 From: Leah Rumancik To: Theodore Ts'o 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: 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). > Just to make sure I understand correctly, the explicit __u32 is critical due to the size being read in by the ioctl, specifically through copy_from_user? When do you switch from __u32 to unsigned long? I don't see the __* types being carried throughout. (Also, just got Darrick's reply about the 32 vs. 64. Yes, originally went with 64 because there was an argument for it. I believe the 32 is likely sufficient, but I don't feel that strongly about this matter) > 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 > Why call them JBD2_JOURNAL_FLUSH* instead of JBD2_JOURNAL_ERASE* since they get passed directly through to the erase function? I feel like it would be weird if someone wanted to use the erase function directly but had to use JBD2_JOURNAL_FLUSH* flags. > if ((flags & ~JBD2_JOURNAL_FLUSH_VALID) || > ((flags & JBD2_JOURNAL_FLUSH_DISCARD) && > (flags & JBD2_JOURNAL_FLUSH_ZEROOUT))) > return -EINVAL; > Ah, great. Thanks! > > + > > + 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); > I'll play around with this and see if I can get it to work. Seems like it might simplify the code a bit. > ... and then let block_start and block_stop be initialized in a single > place. Do you agree? Does this make sense to you? > > - Ted Thanks! Leah