MIME-Version: 1.0
In-Reply-To: <CA+55aFzosQ+Jo6fH2qr5s5YDPvW=CkTGokOLB0tYjZp6ujj3Nw@mail.gmail.com>
References: <Pine.LNX.4.64.1211272252260.18338@file.rdu.redhat.com>
 <50B5CC5A.8060607@kernel.dk> <Pine.LNX.4.64.1211281222410.11599@file.rdu.redhat.com>
 <CA+55aFx4zYnEsUyGJurBjB0XZ0AgmyKqW-+KWVDvma3w6csnHQ@mail.gmail.com>
 <20121128194314.GF4939@ZenIV.linux.org.uk> <Pine.LNX.4.64.1211281630150.5283@file.rdu.redhat.com>
 <CA+55aFziCW_ywZACGoVyNSgy8mToAGhSbdo0VoUAaGvgSb2XxQ@mail.gmail.com>
 <CA+55aFxt655WfuhjOCnu3esg3gt=L37v=ofWfjs+qpXjn-F2uA@mail.gmail.com>
 <20121129191503.GB3490@shiny> <CA+55aFxaHuxaEezkpmGRi4kFGaQFTv9S89N-hJhxBjVa6ZwnbQ@mail.gmail.com>
 <20121129194840.GC3490@shiny> <CA+55aFzosQ+Jo6fH2qr5s5YDPvW=CkTGokOLB0tYjZp6ujj3Nw@mail.gmail.com>
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 29 Nov 2012 12:10:53 -0800
Message-ID: <CA+55aFw=-cN2wrRJ0bcktn=oc6JKSfOPDSF3GsBosDB5fOzozw@mail.gmail.com>
Subject: Re: [PATCH v2] Do a proper locking for mmap and block size change
To: Chris Mason <chris.mason@fusionio.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Chris Mason <clmason@fusionio.com>,
        Mikulas Patocka <mpatocka@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>, Jens Axboe <axboe@kernel.dk>,
        Jeff Chua <jeff.chua.linux@gmail.com>,
        Lai Jiangshan <laijs@cn.fujitsu.com>, Jan Kara <jack@suse.cz>,
        lkml <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Content-Type: text/plain; charset=ISO-8859-1
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 941
Lines: 27

On Thu, Nov 29, 2012 at 11:55 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> The blkdev_get_blocks() this is just sad.
>
> The underlying data structure is actually byte-based (it's
> "i_size_read(bdev->bd_inode"), but we convert it to a block-based
> number.
>
> Oops.

Oh, it's even worse than that. The DIO code ends up passing in buffer
heads that have sizes bigger than the inode i_blksize, which can cause
problems at the end of the disk. So blkdev_get_blocks() knows about
it, and will then "fix" that and shrink them down. The games with
"max_block" are hilarious.

In a really sad way.

That whole blkdev_get_blocks() function is pure and utter shit.

              Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/