From: Matthew Wilcox <willy@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, willy@linux.intel.com,
Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: [PATCH v10 19/21] xip: Add xip_zero_page_range
Date: Thu, 4 Sep 2014 17:08:02 -0400 [thread overview]
Message-ID: <20140904210802.GA27730@localhost.localdomain> (raw)
In-Reply-To: <20140903092116.GF20473@dastard>
On Wed, Sep 03, 2014 at 07:21:16PM +1000, Dave Chinner wrote:
> > @@ -481,9 +484,14 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
> > err = dax_get_addr(&bh, &addr, inode->i_blkbits);
> > if (err < 0)
> > return err;
> > + /*
> > + * ext4 sometimes asks to zero past the end of a block. It
> > + * really just wants to zero to the end of the block.
> > + */
> > + length = min_t(unsigned, length, PAGE_CACHE_SIZE - offset);
> > memset(addr + offset, 0, length);
>
> Sorry, what?
>
> You introduce that bug with the way dax_truncate_page() is redefined
> to always pass PAGE_CACHE_SIZE a a length later on in this patch.
> into the function. That's hardly an ext4 bug....
ext4 does (or did?) have this bug (expectation?). I then take advantage
of the fact that we have to accommodate it, so there are now two places
that have to accommodate it. I forget what the path was that has that
assumption, but xfstests used to display it.
I'm away this week (... bad timing), but I can certainly fix it elsewhere
in ext4 next week.
> > int dax_clear_blocks(struct inode *, sector_t block, long size);
> > +int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
> > int dax_truncate_page(struct inode *, loff_t from, get_block_t);
>
> It's still defined as a function that doesn't exist now....
Oops.
> > +/* Can't be a function because PAGE_CACHE_SIZE is defined in pagemap.h */
> > +#define dax_truncate_page(inode, from, get_block) \
> > + dax_zero_page_range(inode, from, PAGE_CACHE_SIZE, get_block)
>
> And then redefined as a macro here.
Heh, which means we never notice the stale delaration above. Thanks, C!
> This is wrong, IMO,
> dax_truncate_page() should remain as a function and it should
> correctly calculate how much of the page shoul dbe trimmed, not
> leave landmines that other code has to clean up...
>
> (Yup, I'm tracking down a truncate bug in XFS from fsx...)
I'll put an assert in the rewrite, make sure that nobody's trying to
overtruncate.
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next prev parent reply other threads:[~2014-09-04 21:08 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-27 3:45 [PATCH v10 00/21] Support ext4 on NV-DIMMs Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 01/21] axonram: Fix bug in direct_access Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 02/21] Change direct_access calling convention Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 03/21] Fix XIP fault vs truncate race Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 04/21] Allow page fault handlers to perform the COW Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 05/21] Introduce IS_DAX(inode) Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 06/21] Add copy_to_iter(), copy_from_iter() and iov_iter_zero() Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 07/21] Replace XIP read and write with DAX I/O Matthew Wilcox
2014-09-14 14:11 ` Boaz Harrosh
2014-08-27 3:45 ` [PATCH v10 08/21] Replace ext2_clear_xip_target with dax_clear_blocks Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 09/21] Replace the XIP page fault handler with the DAX page fault handler Matthew Wilcox
2014-09-03 7:47 ` Dave Chinner
2014-09-10 15:23 ` Matthew Wilcox
2014-09-11 3:09 ` Dave Chinner
2014-09-24 15:43 ` Matthew Wilcox
2014-09-25 1:01 ` Dave Chinner
2014-08-27 3:45 ` [PATCH v10 10/21] Replace xip_truncate_page with dax_truncate_page Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 11/21] Replace XIP documentation with DAX documentation Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 12/21] Remove get_xip_mem Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 13/21] ext2: Remove ext2_xip_verify_sb() Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 14/21] ext2: Remove ext2_use_xip Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 15/21] ext2: Remove xip.c and xip.h Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 16/21] Remove CONFIG_EXT2_FS_XIP and rename CONFIG_FS_XIP to CONFIG_FS_DAX Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 17/21] ext2: Remove ext2_aops_xip Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 18/21] Get rid of most mentions of XIP in ext2 Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 19/21] xip: Add xip_zero_page_range Matthew Wilcox
2014-09-03 9:21 ` Dave Chinner
2014-09-04 21:08 ` Matthew Wilcox [this message]
2014-09-04 21:36 ` Theodore Ts'o
2014-09-08 18:59 ` Matthew Wilcox
2014-08-27 3:45 ` [PATCH v10 20/21] ext4: Add DAX functionality Matthew Wilcox
2014-09-03 11:13 ` Dave Chinner
2014-09-10 16:49 ` Boaz Harrosh
2014-09-11 4:38 ` Dave Chinner
2014-09-14 12:25 ` Boaz Harrosh
2014-09-15 6:15 ` Dave Chinner
2014-09-15 9:41 ` Boaz Harrosh
2014-08-27 3:45 ` [PATCH v10 21/21] brd: Rename XIP to DAX Matthew Wilcox
2014-08-27 20:06 ` [PATCH v10 00/21] Support ext4 on NV-DIMMs Andrew Morton
2014-08-27 21:12 ` Matthew Wilcox
2014-08-27 21:46 ` Andrew Morton
2014-08-28 1:30 ` Andy Lutomirski
2014-08-28 16:50 ` Matthew Wilcox
2014-08-28 15:45 ` Matthew Wilcox
2014-08-27 21:22 ` Christoph Lameter
2014-08-27 21:30 ` Andrew Morton
2014-08-27 23:04 ` One Thousand Gnomes
2014-08-28 7:17 ` Dave Chinner
2014-08-30 23:11 ` Christian Stroetmann
2014-08-28 8:08 ` Boaz Harrosh
2014-08-28 22:09 ` Zwisler, Ross
2014-09-03 12:05 ` [PATCH 1/1] xfs: add DAX support Dave Chinner
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