From: Eric Biggers <ebiggers@kernel.org> To: Chao Yu <chao@kernel.org> Cc: linux-f2fs-devel@lists.sourceforge.net, Jaegeuk Kim <jaegeuk@kernel.org>, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, Satya Tangirala <satyaprateek2357@gmail.com>, Changheun Lee <nanich.lee@samsung.com>, Matthew Bobrowski <mbobrowski@mbobrowski.org> Subject: Re: [PATCH 3/9] f2fs: rework write preallocations Date: Sun, 25 Jul 2021 10:57:15 -0700 [thread overview] Message-ID: <YP2l+1umf9ct/4Sp@sol.localdomain> (raw) In-Reply-To: <14782036-f6a5-878a-d21f-e7dd7008a285@kernel.org> On Sun, Jul 25, 2021 at 06:50:51PM +0800, Chao Yu wrote: > On 2021/7/16 22:39, Eric Biggers wrote: > > From: Eric Biggers <ebiggers@google.com> > > > > f2fs_write_begin() assumes that all blocks were preallocated by > > default unless FI_NO_PREALLOC is explicitly set. This invites data > > corruption, as there are cases in which not all blocks are preallocated. > > Commit 47501f87c61a ("f2fs: preallocate DIO blocks when forcing > > buffered_io") fixed one case, but there are others remaining. > > Could you please explain which cases we missed to handle previously? > then I can check those related logic before and after the rework. Any case where a buffered write happens while not all blocks were preallocated but FI_NO_PREALLOC wasn't set. For example when ENOSPC was hit in the middle of the preallocations for a direct write that will fall back to a buffered write, e.g. due to f2fs_force_buffered_io() or page cache invalidation failure. > > > - /* > > - * If force_buffere_io() is true, we have to allocate > > - * blocks all the time, since f2fs_direct_IO will fall > > - * back to buffered IO. > > - */ > > - if (!f2fs_force_buffered_io(inode, iocb, from) && > > - f2fs_lfs_mode(F2FS_I_SB(inode))) > > - goto write; > > We should keep this OPU DIO logic, otherwise, in lfs mode, write dio > will always allocate two block addresses for each 4k append IO. > > I jsut test based on codes of last f2fs dev-test branch. Yes, I had misread that due to the weird goto and misleading comment and translated it into: /* If it will be an in-place direct write, don't bother. */ if (dio && !f2fs_lfs_mode(sbi)) return 0; It should be: if (dio && f2fs_lfs_mode(sbi)) return 0; Do you have a proper explanation for why preallocations shouldn't be done in this case? Note that preallocations are still done for buffered writes, which may be out-of-place as well; how are those different? - Eric
WARNING: multiple messages have this Message-ID (diff)
From: Eric Biggers <ebiggers@kernel.org> To: Chao Yu <chao@kernel.org> Cc: Satya Tangirala <satyaprateek2357@gmail.com>, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, Matthew Bobrowski <mbobrowski@mbobrowski.org>, Changheun Lee <nanich.lee@samsung.com>, linux-fsdevel@vger.kernel.org, Jaegeuk Kim <jaegeuk@kernel.org> Subject: Re: [f2fs-dev] [PATCH 3/9] f2fs: rework write preallocations Date: Sun, 25 Jul 2021 10:57:15 -0700 [thread overview] Message-ID: <YP2l+1umf9ct/4Sp@sol.localdomain> (raw) In-Reply-To: <14782036-f6a5-878a-d21f-e7dd7008a285@kernel.org> On Sun, Jul 25, 2021 at 06:50:51PM +0800, Chao Yu wrote: > On 2021/7/16 22:39, Eric Biggers wrote: > > From: Eric Biggers <ebiggers@google.com> > > > > f2fs_write_begin() assumes that all blocks were preallocated by > > default unless FI_NO_PREALLOC is explicitly set. This invites data > > corruption, as there are cases in which not all blocks are preallocated. > > Commit 47501f87c61a ("f2fs: preallocate DIO blocks when forcing > > buffered_io") fixed one case, but there are others remaining. > > Could you please explain which cases we missed to handle previously? > then I can check those related logic before and after the rework. Any case where a buffered write happens while not all blocks were preallocated but FI_NO_PREALLOC wasn't set. For example when ENOSPC was hit in the middle of the preallocations for a direct write that will fall back to a buffered write, e.g. due to f2fs_force_buffered_io() or page cache invalidation failure. > > > - /* > > - * If force_buffere_io() is true, we have to allocate > > - * blocks all the time, since f2fs_direct_IO will fall > > - * back to buffered IO. > > - */ > > - if (!f2fs_force_buffered_io(inode, iocb, from) && > > - f2fs_lfs_mode(F2FS_I_SB(inode))) > > - goto write; > > We should keep this OPU DIO logic, otherwise, in lfs mode, write dio > will always allocate two block addresses for each 4k append IO. > > I jsut test based on codes of last f2fs dev-test branch. Yes, I had misread that due to the weird goto and misleading comment and translated it into: /* If it will be an in-place direct write, don't bother. */ if (dio && !f2fs_lfs_mode(sbi)) return 0; It should be: if (dio && f2fs_lfs_mode(sbi)) return 0; Do you have a proper explanation for why preallocations shouldn't be done in this case? Note that preallocations are still done for buffered writes, which may be out-of-place as well; how are those different? - Eric _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
next prev parent reply other threads:[~2021-07-25 17:57 UTC|newest] Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-16 14:39 [PATCH 0/9] f2fs: use iomap for direct I/O Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-16 14:39 ` [PATCH 1/9] f2fs: make f2fs_write_failed() take struct inode Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-25 10:00 ` Chao Yu 2021-07-25 10:00 ` [f2fs-dev] " Chao Yu 2021-07-16 14:39 ` [PATCH 2/9] f2fs: remove allow_outplace_dio() Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-19 8:41 ` Christoph Hellwig 2021-07-19 8:41 ` [f2fs-dev] " Christoph Hellwig 2021-07-16 14:39 ` [PATCH 3/9] f2fs: rework write preallocations Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-25 10:50 ` Chao Yu 2021-07-25 10:50 ` [f2fs-dev] " Chao Yu 2021-07-25 17:57 ` Eric Biggers [this message] 2021-07-25 17:57 ` Eric Biggers 2021-07-27 2:00 ` Jaegeuk Kim 2021-07-27 2:00 ` [f2fs-dev] " Jaegeuk Kim 2021-07-27 3:23 ` Chao Yu 2021-07-27 3:23 ` [f2fs-dev] " Chao Yu 2021-07-27 7:38 ` Eric Biggers 2021-07-27 7:38 ` [f2fs-dev] " Eric Biggers 2021-07-27 8:30 ` Chao Yu 2021-07-27 8:30 ` [f2fs-dev] " Chao Yu 2021-07-27 15:33 ` Darrick J. Wong 2021-07-27 15:33 ` [f2fs-dev] " Darrick J. Wong 2021-07-29 0:26 ` Chao Yu 2021-07-29 0:26 ` [f2fs-dev] " Chao Yu 2021-07-28 2:29 ` Jaegeuk Kim 2021-07-28 2:29 ` [f2fs-dev] " Jaegeuk Kim 2021-07-25 15:35 ` Jaegeuk Kim 2021-07-25 15:35 ` [f2fs-dev] " Jaegeuk Kim 2021-07-25 15:47 ` Jaegeuk Kim 2021-07-25 15:47 ` [f2fs-dev] " Jaegeuk Kim 2021-07-25 18:01 ` Eric Biggers 2021-07-25 18:01 ` [f2fs-dev] " Eric Biggers 2021-07-26 19:04 ` Jaegeuk Kim 2021-07-26 19:04 ` [f2fs-dev] " Jaegeuk Kim 2021-07-16 14:39 ` [PATCH 4/9] f2fs: reduce indentation in f2fs_file_write_iter() Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-16 14:39 ` [PATCH 5/9] f2fs: fix the f2fs_file_write_iter tracepoint Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-16 14:39 ` [PATCH 6/9] f2fs: implement iomap operations Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-19 8:59 ` Christoph Hellwig 2021-07-19 8:59 ` [f2fs-dev] " Christoph Hellwig 2021-07-22 20:47 ` Jaegeuk Kim 2021-07-22 20:47 ` [f2fs-dev] " Jaegeuk Kim 2021-07-22 20:49 ` Jaegeuk Kim 2021-07-22 20:49 ` [f2fs-dev] " Jaegeuk Kim 2021-07-22 20:54 ` Eric Biggers 2021-07-22 20:54 ` [f2fs-dev] " Eric Biggers 2021-07-22 21:57 ` Jaegeuk Kim 2021-07-22 21:57 ` [f2fs-dev] " Jaegeuk Kim 2021-07-23 1:52 ` Eric Biggers 2021-07-23 1:52 ` [f2fs-dev] " Eric Biggers 2021-07-23 5:00 ` Christoph Hellwig 2021-07-23 5:00 ` [f2fs-dev] " Christoph Hellwig 2021-07-23 8:05 ` Eric Biggers 2021-07-23 8:05 ` [f2fs-dev] " Eric Biggers 2021-07-16 14:39 ` [PATCH 7/9] f2fs: use iomap for direct I/O reads Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-16 14:39 ` [PATCH 8/9] f2fs: use iomap for direct I/O writes Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers 2021-07-16 14:39 ` [PATCH 9/9] f2fs: remove f2fs_direct_IO() Eric Biggers 2021-07-16 14:39 ` [f2fs-dev] " Eric Biggers
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