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Wed, 06 May 2020 08:47:27 +0200 Date: Wed, 6 May 2020 14:47:19 +0800 From: Gao Xiang To: Eric Biggers Message-ID: <20200506064709.GA25482@hsiangkao-HP-ZHAN-66-Pro-G1> References: <20200505153139.201697-1-jaegeuk@kernel.org> <20200505165847.GA98848@gmail.com> <20200505181323.GA55221@google.com> <20200505181941.GC98848@gmail.com> <20200506001403.GA2101@hsiangkao-HP-ZHAN-66-Pro-G1> <20200506012428.GG128280@sol.localdomain> <20200506015813.GA9256@hsiangkao-HP-ZHAN-66-Pro-G1> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200506015813.GA9256@hsiangkao-HP-ZHAN-66-Pro-G1> User-Agent: Mutt/1.10.1 (2018-07-13) X-Provags-ID: V03:K1:z6dtdIcZRcSYYph0RGMRdGYvIpDIYF8mz+BYGilcVnLYpEXyg/g mFR8hgBLc0U/As4vQQXjMXzV40093msxEuzJUUh8FIhgivuJI9T50alip1rHMHI6VGfOi0w 5auoIOjOQZbm123Z5TvIA+Lk63KkQ3ai6p+cyDk0MQwedoKnjMp5OTzdMOzO+k9d+YB2Ko0 uU0i4dijVkg60MGHVFpoQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:spzX94Rvc9Y=:Wwm8mk3c5+AdN+K91dNCm9 /dp58Sb+t6/IYOi1wtRT9WN/nKeLuzqqboXLS/vv6yk90m0vaESkL0mweBW4JyzO7G7RA77tG X3Vn4kZ0AOfvheD/63jfo6RzGHHdw6BqYYbUCgcauVVmDckhx2+LeRCO6r2ozabkBpHay7XJp BKkrqEFrdXe+hMGBMmgtUZwXgolyrS53FdoLcebX18G//mG2tklxmIz+slXZoR5EJMUkQz3Wh d6OYawIFALwHx9omWBJwB/hogCcezV7CIqWLBamcxjHg1ap8bHpjgyrIkG8MkECMImmf76YmY S3mY2EwkFGCBaqRf5wEbt8M/06cYZHJRzDwoqpSOF0iJ1WiSwoxOGl85HcJIfe9m+uYxaTOUf 5T7ps0It5C+fTS7xtqKSwtnagOnPgCfgP4zXLqyYaf8SoU2Dxx8M6Ck32cj/Bsu9mVfYsBLBa n/hTY3TLlBW810WpguEYXCmDfikbx7QEDaFaFKPNR1XXAuLV0ncoNDJJPc8zieleT1uEF+SA9 WlIkeRfqX+2Ll9urFmSAibDl6z4tRhg+2PiHkJ7vtVczxfDpQGCSHyToMqN/7DuGEQZf/iThN odgg2Vf6kNxKaXUl2KBZbWullaQ6kEgjGoJlzB2ZIaon4JlcnXKNMUoPn7YYE5rY29baJSNY9 4iZDI6vTbUDRcecpxrWJxFYB6rCUPGRDGHkHezsxfrIeLH4ep5uv6wdXbUmPWMtS4kaKaWpBq TdlbpEOlz7lTEQsuRijSAqrRbs4BuaACbmfp4Jr4nbMCsC3OS8tkBrgWC30J1AaZoMnL+8V3B Y2Ygy5w0DzKafUdXr2Xyq4FUpWk72s8hgMfND6QFPDRw20XBMafYCodZdAWXlsc417Fr7roc+ G5KnwQh+tvP5G/hYYsNozpDqfqb0nUnMr/Q6f5kFfzmKYEvElBhkDpUTu5Rkc4WBTDgqUwym9 8lOdShEfZGEZ3PDuCRfUk+Yqh2rSICFZ1IPVHM1aHqsikGhVcUoKoyOdhtaZ0HREF/FW2MMSt cERaqxV8uSRCTQw/sxkMwuePsA8faxZZK4GXIRwvfxn3APnqRMHAFxJqMvDKZHOmhhHSSLYko VTifxOe8wazQWUzkWuQw+1pKojOphgbCITYATckXAWTSgR9HvehSaj+wMeaRoviWLR3P8ue5t Yo+IXIZMHsp6QUWZHRg1b6NN3GKv2lfckqFEumXl7DRUnfDRDPXKXqHXdrqLSMj14+4kdo/aw nNKZNeOJeTpvtsayc X-Headers-End: 1jWDqD-00CP1I-Av Subject: Re: [f2fs-dev] [PATCH] f2fs: get parent inode when recovering pino X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jaegeuk Kim , kernel-team@android.com, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Wed, May 06, 2020 at 09:58:22AM +0800, Gao Xiang wrote: > On Tue, May 05, 2020 at 06:24:28PM -0700, Eric Biggers wrote: > > On Wed, May 06, 2020 at 08:14:07AM +0800, Gao Xiang wrote: > > > > > > > > Actually, I think this is wrong because the fsync can be done via a file > > > > descriptor that was opened to a now-deleted link to the file. > > > > > > I'm still confused about this... > > > > > > I don't know what's wrong with this version from my limited knowledge? > > > inode itself is locked when fsyncing, so > > > > > > if the fsync inode->i_nlink == 1, this inode has only one hard link > > > (not deleted yet) and should belong to a single directory; and > > > > > > the only one parent directory would not go away (not deleted as well) > > > since there are some dirents in it (not empty). > > > > > > Could kindly explain more so I would learn more about this scenario? > > > Thanks a lot! > > > > i_nlink == 1 just means that there is one non-deleted link. There can be links > > that have since been deleted, and file descriptors can still be open to them. > > Thanks for your inspiration. You are right, thanks. > > Correct my words... I didn't check f2fs code just now, it seems f2fs doesn't > take inode_lock as some other fs like __generic_file_fsync or ubifs_fsync. > > And i_sem locks nlink / try_to_fix_pino similarly in some extent. It seems > no race by using d_find_alias here. Thanks again. > (think more little bit just now...) Thread 1: Thread 2 (fsync): vfs_unlink try_to_fix_pino f2fs_unlink f2fs_delete_entry f2fs_drop_nlink (i_sem, inode->i_nlink = 1) (... but this dentry still hashed) i_sem, check inode->i_nlink = 1 i_sem d_find_alias d_delete I'm not sure if fsync could still use some wrong alias by chance.. completely untested, maybe just noise... Thanks, Gao Xiang _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel