From: Matthew Wilcox <matthew@wil.cx>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>,
Matthew Wilcox <matthew.r.wilcox@intel.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH v5 22/22] XIP: Add support for unwritten extents
Date: Mon, 27 Jan 2014 20:49:00 -0700 [thread overview]
Message-ID: <20140128034859.GC20939@parisc-linux.org> (raw)
In-Reply-To: <alpine.OSX.2.00.1401271617570.9254@scrumpy>
On Mon, Jan 27, 2014 at 04:32:07PM -0700, Ross Zwisler wrote:
> It looks like we have an additional bit of complexity with the hole case. The
> issue is that for holes, bh->b_size is just the full size of the write as set
> earlier in the function:
>
> bh->b_size = ALIGN(end - offset, PAGE_SIZE);
>
> >From this code it seems like you hoped the call into get_block() would adjust
> bh->b_size to the size of the hole, allowing you to zero just the hole space
> in the user buffer. It doesn't look like it does, though, at least for ext4.
Argh. I got confused. ext4 *has* this information, it just doesn't
propagate it into the bh if it's a hole! Should it? The comments in
the direct IO code imply that it *may*, but doesn't *have* to. What it's
doing now (not touching it) is probably wrong.
> To just assume the current FS block is a hole, we can do something like this:
Yes, this should fix things on an interim basis. Bit inefficient,
but it'll work.
> diff --git a/fs/xip.c b/fs/xip.c
> index 35e401e..e902593 100644
> --- a/fs/xip.c
> +++ b/fs/xip.c
> @@ -122,7 +122,7 @@ static ssize_t xip_io(int rw, struct inode *inode, const struct
>
> if (hole) {
> addr = NULL;
> - size = bh->b_size - first;
> + size = (1 << inode->i_blkbits) - first;
> } else {
> retval = xip_get_addr(inode, bh, &addr);
> if (retval < 0)
>
> --
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--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
next prev parent reply other threads:[~2014-01-28 3:49 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-16 1:24 [PATCH v5 00/22] Rewrite XIP code and add XIP support to ext4 Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 01/22] Fix XIP fault vs truncate race Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 02/22] Allow page fault handlers to perform the COW Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 03/22] axonram: Fix bug in direct_access Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 04/22] Change direct_access calling convention Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 05/22] Introduce IS_XIP(inode) Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 06/22] Treat XIP like O_DIRECT Matthew Wilcox
2014-01-31 16:59 ` Jan Kara
2014-01-16 1:24 ` [PATCH v5 07/22] Rewrite XIP page fault handling Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 08/22] Change xip_truncate_page to take a get_block parameter Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 09/22] Remove mm/filemap_xip.c Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 10/22] Remove get_xip_mem Matthew Wilcox
2014-01-16 1:46 ` Randy Dunlap
2014-01-27 13:26 ` Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 11/22] Replace ext2_clear_xip_target with xip_clear_blocks Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 12/22] ext2: Remove ext2_xip_verify_sb() Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 13/22] ext2: Remove ext2_use_xip Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 14/22] ext2: Remove xip.c and xip.h Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 15/22] Remove CONFIG_EXT2_FS_XIP Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 16/22] ext2: Remove ext2_aops_xip Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 17/22] xip: Add xip_zero_page_range Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 18/22] ext4: Make ext4_block_zero_page_range static Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 19/22] ext4: Add XIP functionality Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 20/22] ext4: Fix typos Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 21/22] xip: Add reporting of major faults Matthew Wilcox
2014-01-16 1:24 ` [PATCH v5 22/22] XIP: Add support for unwritten extents Matthew Wilcox
[not found] ` <CEFDA737.22F87%matthew.r.wilcox@intel.com>
2014-01-17 0:00 ` [PATCH v5 19/22] ext4: Add XIP functionality Ross Zwisler
[not found] ` <CEFD7DAD.22F65%matthew.r.wilcox@intel.com>
2014-01-22 22:51 ` [PATCH v5 22/22] XIP: Add support for unwritten extents Ross Zwisler
2014-01-23 12:08 ` Matthew Wilcox
2014-01-23 19:13 ` Ross Zwisler
[not found] ` <CF0C370C.235F1%willy@linux.intel.com>
2014-01-27 23:32 ` Ross Zwisler
2014-01-28 3:49 ` Matthew Wilcox [this message]
2014-01-23 7:48 ` [PATCH v5 00/22] Rewrite XIP code and add XIP support to ext4 Dave Chinner
2014-01-23 7:53 ` Dave Chinner
2014-01-23 9:01 ` Dave Chinner
2014-01-23 12:12 ` Wilcox, Matthew R
2014-01-28 6:06 ` Dave Chinner
2014-01-30 6:42 ` Dave Chinner
2014-01-30 9:25 ` Dave Chinner
2014-01-31 3:06 ` Dave Chinner
2014-01-31 5:45 ` Ross Zwisler
2014-01-31 13:04 ` Dave Chinner
[not found] ` <CF1FF3EB.24114%matthew.r.wilcox@intel.com>
2014-02-11 23:12 ` [PATCH v5 19/22] ext4: Add XIP functionality Ross Zwisler
2014-02-13 0:00 ` Ross Zwisler
[not found] ` <CF215477.24281%matthew.r.wilcox@intel.com>
2014-02-12 23:53 ` [PATCH v5 06/22] Treat XIP like O_DIRECT Ross Zwisler
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