From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-nvdimm@lists.01.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH 11/18] dax: Fix condition for filling of PMD holes
Date: Fri, 29 Apr 2016 13:08:05 -0600 [thread overview]
Message-ID: <20160429190805.GF5888@linux.intel.com> (raw)
In-Reply-To: <1461015341-20153-12-git-send-email-jack@suse.cz>
On Mon, Apr 18, 2016 at 11:35:34PM +0200, Jan Kara wrote:
> Currently dax_pmd_fault() decides to fill a PMD-sized hole only if
> returned buffer has BH_Uptodate set. However that doesn't get set for
> any mapping buffer so that branch is actually a dead code. The
> BH_Uptodate check doesn't make any sense so just remove it.
I'm not sure about this one. In my testing (which was a while ago) I was
also never able to exercise this code path and create huge zero pages. My
concern is that by removing the buffer_uptodate() check, we will all of a
sudden start running through a code path that was previously unreachable.
AFAICT the buffer_uptodate() was part of the original PMD commit. Did we ever
get buffers with BH_Uptodate set? Has this code ever been run? Does it work?
I suppose this concern is mitigated by the fact that later in this series you
disable the PMD path entirely, but maybe we should just leave it as is and
turn it off, then clean it up if/when we reenable it when we add multi-order
radix tree locking for PMDs?
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
> fs/dax.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 237581441bc1..42bf65b4e752 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -878,7 +878,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> goto fallback;
> }
>
> - if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
> + if (!write && !buffer_mapped(&bh)) {
> spinlock_t *ptl;
> pmd_t entry;
> struct page *zero_page = get_huge_zero_page();
> --
> 2.6.6
>
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WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-mm@kvack.org, Ross Zwisler <ross.zwisler@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>,
linux-nvdimm@lists.01.org, Matthew Wilcox <willy@linux.intel.com>
Subject: Re: [PATCH 11/18] dax: Fix condition for filling of PMD holes
Date: Fri, 29 Apr 2016 13:08:05 -0600 [thread overview]
Message-ID: <20160429190805.GF5888@linux.intel.com> (raw)
In-Reply-To: <1461015341-20153-12-git-send-email-jack@suse.cz>
On Mon, Apr 18, 2016 at 11:35:34PM +0200, Jan Kara wrote:
> Currently dax_pmd_fault() decides to fill a PMD-sized hole only if
> returned buffer has BH_Uptodate set. However that doesn't get set for
> any mapping buffer so that branch is actually a dead code. The
> BH_Uptodate check doesn't make any sense so just remove it.
I'm not sure about this one. In my testing (which was a while ago) I was
also never able to exercise this code path and create huge zero pages. My
concern is that by removing the buffer_uptodate() check, we will all of a
sudden start running through a code path that was previously unreachable.
AFAICT the buffer_uptodate() was part of the original PMD commit. Did we ever
get buffers with BH_Uptodate set? Has this code ever been run? Does it work?
I suppose this concern is mitigated by the fact that later in this series you
disable the PMD path entirely, but maybe we should just leave it as is and
turn it off, then clean it up if/when we reenable it when we add multi-order
radix tree locking for PMDs?
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
> fs/dax.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 237581441bc1..42bf65b4e752 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -878,7 +878,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> goto fallback;
> }
>
> - if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
> + if (!write && !buffer_mapped(&bh)) {
> spinlock_t *ptl;
> pmd_t entry;
> struct page *zero_page = get_huge_zero_page();
> --
> 2.6.6
>
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WARNING: multiple messages have this Message-ID (diff)
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-mm@kvack.org, Ross Zwisler <ross.zwisler@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>,
linux-nvdimm@lists.01.org, Matthew Wilcox <willy@linux.intel.com>
Subject: Re: [PATCH 11/18] dax: Fix condition for filling of PMD holes
Date: Fri, 29 Apr 2016 13:08:05 -0600 [thread overview]
Message-ID: <20160429190805.GF5888@linux.intel.com> (raw)
In-Reply-To: <1461015341-20153-12-git-send-email-jack@suse.cz>
On Mon, Apr 18, 2016 at 11:35:34PM +0200, Jan Kara wrote:
> Currently dax_pmd_fault() decides to fill a PMD-sized hole only if
> returned buffer has BH_Uptodate set. However that doesn't get set for
> any mapping buffer so that branch is actually a dead code. The
> BH_Uptodate check doesn't make any sense so just remove it.
I'm not sure about this one. In my testing (which was a while ago) I was
also never able to exercise this code path and create huge zero pages. My
concern is that by removing the buffer_uptodate() check, we will all of a
sudden start running through a code path that was previously unreachable.
AFAICT the buffer_uptodate() was part of the original PMD commit. Did we ever
get buffers with BH_Uptodate set? Has this code ever been run? Does it work?
I suppose this concern is mitigated by the fact that later in this series you
disable the PMD path entirely, but maybe we should just leave it as is and
turn it off, then clean it up if/when we reenable it when we add multi-order
radix tree locking for PMDs?
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
> fs/dax.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 237581441bc1..42bf65b4e752 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -878,7 +878,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> goto fallback;
> }
>
> - if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
> + if (!write && !buffer_mapped(&bh)) {
> spinlock_t *ptl;
> pmd_t entry;
> struct page *zero_page = get_huge_zero_page();
> --
> 2.6.6
>
next prev parent reply other threads:[~2016-04-29 19:08 UTC|newest]
Thread overview: 122+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-18 21:35 [RFC v3] [PATCH 0/18] DAX page fault locking Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` [PATCH 01/18] ext4: Handle transient ENOSPC properly for DAX Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` [PATCH 02/18] ext4: Fix race in transient ENOSPC detection Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` [PATCH 03/18] DAX: move RADIX_DAX_ definitions to dax.c Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` [PATCH 04/18] dax: Remove complete_unwritten argument Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` [PATCH 05/18] ext2: Avoid DAX zeroing to corrupt data Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 16:30 ` Ross Zwisler
2016-04-29 16:30 ` Ross Zwisler
2016-04-29 16:30 ` Ross Zwisler
2016-04-18 21:35 ` [PATCH 06/18] dax: Remove dead zeroing code from fault handlers Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 16:48 ` Ross Zwisler
2016-04-18 21:35 ` [PATCH 07/18] ext4: Refactor direct IO code Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` [PATCH 08/18] ext4: Pre-zero allocated blocks for DAX IO Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 18:01 ` Ross Zwisler
2016-04-29 18:01 ` Ross Zwisler
2016-04-29 18:01 ` Ross Zwisler
2016-05-02 13:09 ` Jan Kara
2016-05-02 13:09 ` Jan Kara
2016-04-18 21:35 ` [PATCH 09/18] dax: Remove zeroing from dax_io() Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 18:56 ` Ross Zwisler
2016-04-29 18:56 ` Ross Zwisler
2016-04-18 21:35 ` [PATCH 10/18] dax: Remove pointless writeback from dax_do_io() Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 19:00 ` Ross Zwisler
2016-04-29 19:00 ` Ross Zwisler
2016-04-29 19:00 ` Ross Zwisler
2016-04-18 21:35 ` [PATCH 11/18] dax: Fix condition for filling of PMD holes Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 19:08 ` Ross Zwisler [this message]
2016-04-29 19:08 ` Ross Zwisler
2016-04-29 19:08 ` Ross Zwisler
2016-05-02 13:16 ` Jan Kara
2016-05-02 13:16 ` Jan Kara
2016-04-18 21:35 ` [PATCH 12/18] dax: Remove redundant inode size checks Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` [PATCH 13/18] dax: Make huge page handling depend of CONFIG_BROKEN Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 19:53 ` Ross Zwisler
2016-04-29 19:53 ` Ross Zwisler
2016-05-02 13:19 ` Jan Kara
2016-05-02 13:19 ` Jan Kara
2016-05-02 13:19 ` Jan Kara
2016-04-18 21:35 ` [PATCH 14/18] dax: Define DAX lock bit for radix tree exceptional entry Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 20:03 ` Ross Zwisler
2016-04-29 20:03 ` Ross Zwisler
2016-04-29 20:03 ` Ross Zwisler
2016-04-18 21:35 ` [PATCH 15/18] dax: Allow DAX code to replace exceptional entries Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-29 20:29 ` Ross Zwisler
2016-04-29 20:29 ` Ross Zwisler
2016-04-18 21:35 ` [PATCH 16/18] dax: New fault locking Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-27 4:27 ` NeilBrown
2016-04-27 4:27 ` NeilBrown
2016-05-06 4:13 ` Ross Zwisler
2016-05-06 4:13 ` Ross Zwisler
2016-05-06 4:13 ` Ross Zwisler
2016-05-10 12:27 ` Jan Kara
2016-05-10 12:27 ` Jan Kara
2016-05-11 19:26 ` Ross Zwisler
2016-05-11 19:26 ` Ross Zwisler
2016-05-12 7:58 ` Jan Kara
2016-05-12 7:58 ` Jan Kara
2016-04-18 21:35 ` [PATCH 17/18] dax: Use radix tree entry lock to protect cow faults Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-19 11:46 ` Jerome Glisse
2016-04-19 11:46 ` Jerome Glisse
2016-04-19 11:46 ` Jerome Glisse
2016-04-19 14:33 ` Jan Kara
2016-04-19 14:33 ` Jan Kara
2016-04-19 14:33 ` Jan Kara
2016-04-19 15:19 ` Jerome Glisse
2016-04-19 15:19 ` Jerome Glisse
2016-04-19 15:19 ` Jerome Glisse
2016-04-19 15:19 ` Jerome Glisse
2016-04-18 21:35 ` [PATCH 18/18] dax: Remove i_mmap_lock protection Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-04-18 21:35 ` Jan Kara
2016-05-06 3:35 ` [RFC v3] [PATCH 0/18] DAX page fault locking Ross Zwisler
2016-05-06 3:35 ` Ross Zwisler
2016-05-06 20:33 ` Ross Zwisler
2016-05-06 20:33 ` Ross Zwisler
2016-05-09 9:38 ` Jan Kara
2016-05-09 9:38 ` Jan Kara
2016-05-09 9:38 ` Jan Kara
2016-05-10 15:28 ` Jan Kara
2016-05-10 15:28 ` Jan Kara
2016-05-10 15:28 ` Jan Kara
2016-05-10 20:30 ` Ross Zwisler
2016-05-10 20:30 ` Ross Zwisler
2016-05-10 20:30 ` Ross Zwisler
2016-05-10 22:39 ` Ross Zwisler
2016-05-10 22:39 ` Ross Zwisler
2016-05-11 9:19 ` Jan Kara
2016-05-11 9:19 ` Jan Kara
2016-05-11 9:19 ` Jan Kara
2016-05-11 15:52 ` Ross Zwisler
2016-05-11 15:52 ` Ross Zwisler
2016-05-11 15:52 ` Ross Zwisler
2016-05-09 21:28 ` Verma, Vishal L
2016-05-10 11:52 ` Jan Kara
2016-05-10 11:52 ` Jan Kara
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