Re: [PATCH RFC v2 for-6.8/block 15/18] buffer: add a new helper to read sb block

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

Hi,

在 2023/12/12 1:27, Jan Kara 写道:
> On Mon 11-12-23 22:07:53, Yu Kuai wrote:
> > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> >
> > Unlike __bread_gfp(), ext4 has special handing while reading sb block:
> >
> > 1) __GFP_NOFAIL is not set, and memory allocation can fail;
> > 2) If buffer write failed before, set buffer uptodate and don't read
> >     block from disk;
> > 3) REQ_META is set for all IO, and REQ_PRIO is set for reading xattr;
> > 4) If failed, return error ptr instead of NULL;
> >
> > This patch add a new helper __bread_gfp2() that will match above 2 and 3(
> > 1 will be used, and 4 will still be encapsulated by ext4), and prepare to
> > prevent calling mapping_gfp_constraint() directly on bd_inode->i_mapping
> > in ext4.
> >
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ...
> > +/*
> > + * This works like __bread_gfp() except:
> > + * 1) If buffer write failed before, set buffer uptodate and don't read
> > + * block from disk;
> > + * 2) Caller can pass in additional op_flags like REQ_META;
> > + */
> > +struct buffer_head *
> > +__bread_gfp2(struct block_device *bdev, sector_t block, unsigned int size,
> > +            blk_opf_t op_flags, gfp_t gfp)
> > +{
> > +       return bread_gfp(bdev, block, size, op_flags, gfp, true);
> > +}
> > +EXPORT_SYMBOL(__bread_gfp2);
> __bread_gfp2() is not a great name, why not just using bread_gfp()
> directly? I'm not a huge fan of boolean arguments but three different flags
> arguments would be too much for my taste ;) so I guess I can live with
> that.
I agree that __bread_gfp2 is not a greate name, if possible, I'll try to
figure out a better name for v3.

Thanks for reviewing this patchset!
Kuai
>                                                                 Honza