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Date: Tue, 15 Jan 2013 11:19:34 +0100
From: Jan Kara <jack@...e.cz>
To: "Darrick J. Wong" <darrick.wong@...cle.com>
Cc: axboe@...nel.dk, lucho@...kov.net, jack@...e.cz, ericvh@...il.com,
tytso@....edu, viro@...iv.linux.org.uk, rminnich@...dia.gov,
martin.petersen@...cle.com, neilb@...e.de, david@...morbit.com,
gnehzuil.liu@...il.com, linux-kernel@...r.kernel.org,
hch@...radead.org, linux-fsdevel@...r.kernel.org,
adilger.kernel@...ger.ca, bharrosh@...asas.com, jlayton@...ba.org,
linux-ext4@...r.kernel.org, hirofumi@...l.parknet.co.jp
Subject: Re: [PATCH 2/6] mm: Only enforce stable page writes if the backing
device requires it
On Mon 14-01-13 21:42:50, Darrick J. Wong wrote:
> Create a helper function to check if a backing device requires stable page
> writes and, if so, performs the necessary wait. Then, make it so that all
> points in the memory manager that handle making pages writable use the helper
> function. This should provide stable page write support to most filesystems,
> while eliminating unnecessary waiting for devices that don't require the
> feature.
Looks good. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
>
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
> fs/buffer.c | 2 +-
> fs/ext4/inode.c | 2 +-
> fs/gfs2/file.c | 2 +-
> fs/nilfs2/file.c | 2 +-
> include/linux/pagemap.h | 1 +
> mm/filemap.c | 3 ++-
> mm/page-writeback.c | 20 ++++++++++++++++++++
> 7 files changed, 27 insertions(+), 5 deletions(-)
>
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index c017a2d..2981449 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2359,7 +2359,7 @@ int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
> if (unlikely(ret < 0))
> goto out_unlock;
> set_page_dirty(page);
> - wait_on_page_writeback(page);
> + wait_for_stable_page(page);
> return 0;
> out_unlock:
> unlock_page(page);
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index cbfe13b..cd818d8b 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4968,7 +4968,7 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> 0, len, NULL,
> ext4_bh_unmapped)) {
> /* Wait so that we don't change page under IO */
> - wait_on_page_writeback(page);
> + wait_for_stable_page(page);
> ret = VM_FAULT_LOCKED;
> goto out;
> }
> diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
> index 991ab2d..b9e0ca2 100644
> --- a/fs/gfs2/file.c
> +++ b/fs/gfs2/file.c
> @@ -483,7 +483,7 @@ out:
> gfs2_holder_uninit(&gh);
> if (ret == 0) {
> set_page_dirty(page);
> - wait_on_page_writeback(page);
> + wait_for_stable_page(page);
> }
> sb_end_pagefault(inode->i_sb);
> return block_page_mkwrite_return(ret);
> diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
> index 6194688..bec4af6 100644
> --- a/fs/nilfs2/file.c
> +++ b/fs/nilfs2/file.c
> @@ -126,7 +126,7 @@ static int nilfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> nilfs_transaction_commit(inode->i_sb);
>
> mapped:
> - wait_on_page_writeback(page);
> + wait_for_stable_page(page);
> out:
> sb_end_pagefault(inode->i_sb);
> return block_page_mkwrite_return(ret);
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 6da609d..0e38e13 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -414,6 +414,7 @@ static inline void wait_on_page_writeback(struct page *page)
> }
>
> extern void end_page_writeback(struct page *page);
> +void wait_for_stable_page(struct page *page);
>
> /*
> * Add an arbitrary waiter to a page's wait queue
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 83efee7..5577dc8 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1728,6 +1728,7 @@ int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> * see the dirty page and writeprotect it again.
> */
> set_page_dirty(page);
> + wait_for_stable_page(page);
> out:
> sb_end_pagefault(inode->i_sb);
> return ret;
> @@ -2274,7 +2275,7 @@ repeat:
> return NULL;
> }
> found:
> - wait_on_page_writeback(page);
> + wait_for_stable_page(page);
> return page;
> }
> EXPORT_SYMBOL(grab_cache_page_write_begin);
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 0713bfb..9c5af4d 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2289,3 +2289,23 @@ int mapping_tagged(struct address_space *mapping, int tag)
> return radix_tree_tagged(&mapping->page_tree, tag);
> }
> EXPORT_SYMBOL(mapping_tagged);
> +
> +/**
> + * wait_for_stable_page() - wait for writeback to finish, if necessary.
> + * @page: The page to wait on.
> + *
> + * This function determines if the given page is related to a backing device
> + * that requires page contents to be held stable during writeback. If so, then
> + * it will wait for any pending writeback to complete.
> + */
> +void wait_for_stable_page(struct page *page)
> +{
> + struct address_space *mapping = page_mapping(page);
> + struct backing_dev_info *bdi = mapping->backing_dev_info;
> +
> + if (!bdi_cap_stable_pages_required(bdi))
> + return;
> +
> + wait_on_page_writeback(page);
> +}
> +EXPORT_SYMBOL_GPL(wait_for_stable_page);
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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