From: Jan Kara <jack@suse.cz>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Jan Kara <jack@suse.cz>,
linux-ext4@vger.kernel.org, Ye Bin <yebin10@huawei.com>
Subject: Re: [PATCH] ext4: use ext4_fc_tl_mem in fast-commit replay path
Date: Thu, 12 Jan 2023 11:10:07 +0100 [thread overview]
Message-ID: <20230112101007.d5ic6uzvj6noh4q7@quack3> (raw)
In-Reply-To: <Y78AO7WX5Q6Zju3p@sol.localdomain>
On Wed 11-01-23 10:30:19, Eric Biggers wrote:
> On Wed, Jan 11, 2023 at 03:43:27PM +0100, Jan Kara wrote:
> > On Fri 16-12-22 21:02:12, Eric Biggers wrote:
> > > From: Eric Biggers <ebiggers@google.com>
> > >
> > > To avoid 'sparse' warnings about missing endianness conversions, don't
> > > store native endianness values into struct ext4_fc_tl. Instead, use a
> > > separate struct type, ext4_fc_tl_mem.
> > >
> > > Fixes: dcc5827484d6 ("ext4: factor out ext4_fc_get_tl()")
> > > Cc: Ye Bin <yebin10@huawei.com>
> > > Signed-off-by: Eric Biggers <ebiggers@google.com>
> >
> > Looks good to me. Just one nit below:
> >
> > > -static inline void ext4_fc_get_tl(struct ext4_fc_tl *tl, u8 *val)
> > > +static inline void ext4_fc_get_tl(struct ext4_fc_tl_mem *tl, u8 *val)
> > > {
> > > - memcpy(tl, val, EXT4_FC_TAG_BASE_LEN);
> > > - tl->fc_len = le16_to_cpu(tl->fc_len);
> > > - tl->fc_tag = le16_to_cpu(tl->fc_tag);
> > > + struct ext4_fc_tl tl_disk;
> > > +
> > > + memcpy(&tl_disk, val, EXT4_FC_TAG_BASE_LEN);
> > > + tl->fc_len = le16_to_cpu(tl_disk.fc_len);
> > > + tl->fc_tag = le16_to_cpu(tl_disk.fc_tag);
> > > }
> >
> > So why not just:
> >
> > struct ext4_fc_tl *tl_disk = (struct ext4_fc_tl *)val;
> >
> > instead of memcpy?
>
> That would result in unaligned memory accesses.
Indeed. Thanks for explanation! Feel free to add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2023-01-12 10:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-17 5:02 [PATCH] ext4: use ext4_fc_tl_mem in fast-commit replay path Eric Biggers
2023-01-11 14:43 ` Jan Kara
2023-01-11 18:30 ` Eric Biggers
2023-01-12 10:10 ` Jan Kara [this message]
2023-02-09 15:56 ` Theodore Ts'o
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