From: Al Viro <viro@ZenIV.linux.org.uk> To: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: Christoph Hellwig <hch@infradead.org>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Brandt <Chris.Brandt@renesas.com> Subject: Re: [PATCH v6 1/4] cramfs: direct memory access support Date: Fri, 13 Oct 2017 18:29:34 +0100 [thread overview] Message-ID: <20171013172934.GG21978@ZenIV.linux.org.uk> (raw) In-Reply-To: <20171012061613.28705-2-nicolas.pitre@linaro.org> On Thu, Oct 12, 2017 at 02:16:10AM -0400, Nicolas Pitre wrote: > static void cramfs_kill_sb(struct super_block *sb) > { > struct cramfs_sb_info *sbi = CRAMFS_SB(sb); > > - kill_block_super(sb); > + if (IS_ENABLED(CCONFIG_CRAMFS_MTD)) { > + if (sbi->mtd_point_size) > + mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size); > + if (sb->s_mtd) > + kill_mtd_super(sb); ... > + mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE); > + err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size, > + &sbi->linear_virt_addr, &sbi->linear_phys_addr); > + if (err || sbi->mtd_point_size != sbi->size) { What happens if that mtd_point() fails? Note that ->kill_sb() will be called anyway and ->mtd_point_size is going to be non-zero here... Do we get the second mtd_unpoint(), or am I misreading that code? This logics does look fishy, but I'm not familiar enough with mtd guts to tell if that's OK... Rules regarding ->kill_sb(): any struct super_block instance that got out of sget() and its ilk will have ->kill_sb() called. In case of mtd, it's simply "if that thing got past setting ->s_mtd, it will be passed to ->kill_sb()". Note, BTW, that you *must* have generic_shutdown_super() called once on every reachable path in ->kill_sb(). AFAICS your patch is correct in that area (all instances with that ->s_type are created either in mount_bdev() or in mount_mtd(); the former will have non-NULL ->s_bdev, the latter - non-NULL ->s_mtd), but that's one thing to watch out when doing any modifications.
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk> To: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: Christoph Hellwig <hch@infradead.org>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Brandt <Chris.Brandt@renesas.com> Subject: Re: [PATCH v6 1/4] cramfs: direct memory access support Date: Fri, 13 Oct 2017 18:29:34 +0100 [thread overview] Message-ID: <20171013172934.GG21978@ZenIV.linux.org.uk> (raw) In-Reply-To: <20171012061613.28705-2-nicolas.pitre@linaro.org> On Thu, Oct 12, 2017 at 02:16:10AM -0400, Nicolas Pitre wrote: > static void cramfs_kill_sb(struct super_block *sb) > { > struct cramfs_sb_info *sbi = CRAMFS_SB(sb); > > - kill_block_super(sb); > + if (IS_ENABLED(CCONFIG_CRAMFS_MTD)) { > + if (sbi->mtd_point_size) > + mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size); > + if (sb->s_mtd) > + kill_mtd_super(sb); ... > + mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE); > + err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size, > + &sbi->linear_virt_addr, &sbi->linear_phys_addr); > + if (err || sbi->mtd_point_size != sbi->size) { What happens if that mtd_point() fails? Note that ->kill_sb() will be called anyway and ->mtd_point_size is going to be non-zero here... Do we get the second mtd_unpoint(), or am I misreading that code? This logics does look fishy, but I'm not familiar enough with mtd guts to tell if that's OK... Rules regarding ->kill_sb(): any struct super_block instance that got out of sget() and its ilk will have ->kill_sb() called. In case of mtd, it's simply "if that thing got past setting ->s_mtd, it will be passed to ->kill_sb()". Note, BTW, that you *must* have generic_shutdown_super() called once on every reachable path in ->kill_sb(). AFAICS your patch is correct in that area (all instances with that ->s_type are created either in mount_bdev() or in mount_mtd(); the former will have non-NULL ->s_bdev, the latter - non-NULL ->s_mtd), but that's one thing to watch out when doing any modifications. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-10-13 17:29 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-10-12 6:16 [PATCH v6 0/4] cramfs refresh for embedded usage Nicolas Pitre 2017-10-12 6:16 ` Nicolas Pitre 2017-10-12 6:16 ` [PATCH v6 1/4] cramfs: direct memory access support Nicolas Pitre 2017-10-12 6:16 ` Nicolas Pitre 2017-10-12 17:03 ` Chris Brandt 2017-10-12 17:03 ` Chris Brandt 2017-10-13 1:20 ` Nicolas Pitre 2017-10-13 1:20 ` Nicolas Pitre 2017-10-13 7:30 ` Christoph Hellwig 2017-10-13 7:30 ` Christoph Hellwig 2017-10-13 17:29 ` Al Viro [this message] 2017-10-13 17:29 ` Al Viro 2017-10-13 17:39 ` Nicolas Pitre 2017-10-13 17:39 ` Nicolas Pitre 2017-10-13 17:52 ` Al Viro 2017-10-13 17:52 ` Al Viro 2017-10-13 18:18 ` Nicolas Pitre 2017-10-13 18:18 ` Nicolas Pitre 2017-10-13 20:09 ` Nicolas Pitre 2017-10-13 20:09 ` Nicolas Pitre 2017-10-14 0:31 ` Al Viro 2017-10-14 0:31 ` Al Viro 2017-10-14 2:25 ` Nicolas Pitre 2017-10-14 2:25 ` Nicolas Pitre 2017-10-14 2:37 ` Nicolas Pitre 2017-10-14 2:37 ` Nicolas Pitre 2017-10-12 6:16 ` [PATCH v6 2/4] cramfs: implement uncompressed and arbitrary data block positioning Nicolas Pitre 2017-10-12 6:16 ` Nicolas Pitre 2017-10-12 6:16 ` [PATCH v6 3/4] cramfs: add mmap support Nicolas Pitre 2017-10-12 6:16 ` Nicolas Pitre 2017-10-13 7:31 ` Christoph Hellwig 2017-10-13 7:31 ` Christoph Hellwig 2017-10-12 6:16 ` [PATCH v6 4/4] cramfs: rehabilitate it Nicolas Pitre 2017-10-12 6:16 ` Nicolas Pitre
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20171013172934.GG21978@ZenIV.linux.org.uk \ --to=viro@zeniv.linux.org.uk \ --cc=Chris.Brandt@renesas.com \ --cc=hch@infradead.org \ --cc=linux-embedded@vger.kernel.org \ --cc=linux-fsdevel@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=nicolas.pitre@linaro.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.