From: Eric Biggers <ebiggers@kernel.org>
To: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [PATCH 3/6] f2fs: do not expose unwritten blocks to user by DIO
Date: Fri, 7 Jan 2022 18:21:26 -0800 [thread overview]
Message-ID: <Ydj1JvEeLo1mrqvb@sol.localdomain> (raw)
In-Reply-To: <YdjucBBopEDuUb5b@google.com>
On Fri, Jan 07, 2022 at 05:52:48PM -0800, Jaegeuk Kim wrote:
> On 01/07, Eric Biggers wrote:
> > Hi Jaegeuk,
> >
> > On Tue, Jan 04, 2022 at 01:24:16PM -0800, Jaegeuk Kim wrote:
> > > DIO preallocates physical blocks before writing data, but if an error occurrs
> > > or power-cut happens, we can see block contents from the disk. This patch tries
> > > to fix it by 1) turning to buffered writes for DIO into holes, 2) truncating
> > > unwritten blocks from error or power-cut.
> > >
> > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > > ---
> > > fs/f2fs/data.c | 5 ++++-
> > > fs/f2fs/f2fs.h | 5 +++++
> > > fs/f2fs/file.c | 27 ++++++++++++++++++---------
> > > fs/f2fs/inode.c | 8 ++++++++
> > > 4 files changed, 35 insertions(+), 10 deletions(-)
> >
> > Unfortunately, this patch doesn't completely fix the uninitialized data
> > exposure. The problem is that it only makes DIO writes fall back to buffered
> > writes for holes, and not for reserved blocks (NEW_ADDR). f2fs's reserved
> > blocks are *not* the same as the unwritten extents that other filesystems have;
> > f2fs's reserved blocks have to be turned into regular blocks before DIO can
> > write to them. That immediately exposes them to concurrent reads (at least
> > buffered reads, but I think DIO reads too).
>
> Isn't it resolved by i_size which gives the written blocks only?
>
I'm not sure what you mean, but this is for non-extending writes, so i_size
isn't relevant.
- Eric
next prev parent reply other threads:[~2022-01-08 2:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-04 21:24 [PATCH 1/6] f2fs: rework write preallocations Jaegeuk Kim
2022-01-04 21:24 ` [PATCH 2/6] f2fs: reduce indentation in f2fs_file_write_iter() Jaegeuk Kim
2022-01-04 21:24 ` [PATCH 3/6] f2fs: do not expose unwritten blocks to user by DIO Jaegeuk Kim
2022-01-05 13:19 ` [f2fs-dev] " Chao Yu
2022-01-05 18:25 ` Jaegeuk Kim
2022-01-07 23:13 ` Eric Biggers
2022-01-08 1:52 ` Jaegeuk Kim
2022-01-08 2:21 ` Eric Biggers [this message]
2022-01-08 3:35 ` Jaegeuk Kim
2022-01-08 4:21 ` Eric Biggers
2022-01-04 21:24 ` [PATCH 4/6] f2fs: fix the f2fs_file_write_iter tracepoint Jaegeuk Kim
2022-01-04 21:24 ` [PATCH 5/6] f2fs: implement iomap operations Jaegeuk Kim
2022-01-05 13:20 ` [f2fs-dev] " Chao Yu
2022-01-05 18:25 ` Jaegeuk Kim
2022-01-04 21:24 ` [PATCH 6/6] f2fs: use iomap for direct I/O Jaegeuk Kim
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