linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: change the way of handling range.len in F2FS_IOC_SEC_TRIM

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Message-ID: <20200710032920.GD545837@google.com>
Date:   Thu, 9 Jul 2020 20:29:20 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Daeho Jeong <daeho43@...il.com>,
        Daeho Jeong <daehojeong@...gle.com>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: change the way of handling range.len in
 F2FS_IOC_SEC_TRIM_FILE

On 07/09, Eric Biggers wrote:
> On Thu, Jul 09, 2020 at 08:20:35PM -0700, Jaegeuk Kim wrote:
> > On 07/10, Daeho Jeong wrote:
> > > 1. The valid data will be within i_size.
> > > 2. All the trim operations will be done in a unit of block, even if
> > > i_size is not aligned with BLKSIZE like the below.
> > > 
> > >         index = F2FS_BYTES_TO_BLK(range.start);
> > >         pg_end = DIV_ROUND_UP(end_addr, F2FS_BLKSIZE);     <= BLKSIZE aligned
> > > 
> > > Are you worried about the case that sudden power-off occurs while a
> > > file is being truncated?
> > > ex) 1GB file is being truncated to 4KB -> sudden power-off ->
> > > i_size(4KB), i_blocks(maybe somewhere between 4KB and 1GB)
> > 
> > Yes. Basically, I believe we can have some data beyond i_size like fsverity.
> > 
> 
> Note that fs-verity files are read-only, and therefore this ioctl can't be used
> on them (since it requires a writable file descriptor).  So that case doesn't
> need to be handled here.

I meant it as an example of valid data beyond i_size.

> 
> - Eric