Re: [PATCH V4 4/8] Cleancache: VFS hooks for cleancache

[Jeremy Fitzhardinge]

 On 08/30/2010 03:32 PM, Dan Magenheimer wrote:
> [PATCH V4 4/8] Cleancache: VFS hooks for cleancache
>
> Implement core hooks in VFS for: initializing cleancache
> per filesystem; capturing clean pages evicted by page cache;
> attempting to get pages from cleancache before filesystem
> read; and ensuring coherency between pagecache, disk,
> and cleancache.  All hooks become no-ops if CONFIG_CLEANCACHE
> is unset, or become compare-function-pointer-to-NULL if
> CONFIG_CLEANCACHE is set but no cleancache "backend" has
> claimed cleancache_ops.
>
> Signed-off-by: Chris Mason <chris.mason@xxxxxxxxxx>
> Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
>
> Diffstat:
>  fs/buffer.c                              |    5 +++++
>  fs/mpage.c                               |    7 +++++++
>  fs/super.c                               |    7 +++++++
>  mm/filemap.c                             |   11 +++++++++++
>  mm/truncate.c                            |   10 ++++++++++
>  5 files changed, 40 insertions(+)
>
> --- linux-2.6.36-rc3/fs/super.c	2010-08-29 09:36:04.000000000 -0600
> +++ linux-2.6.36-rc3-cleancache/fs/super.c	2010-08-30 09:20:43.000000000 -0600
> @@ -30,6 +30,7 @@
>  #include <linux/idr.h>
>  #include <linux/mutex.h>
>  #include <linux/backing-dev.h>
> +#include <linux/cleancache.h>
>  #include "internal.h"
>  
>  
> @@ -110,6 +111,7 @@ static struct super_block *alloc_super(s
>  		s->s_maxbytes = MAX_NON_LFS;
>  		s->s_op = &default_op;
>  		s->s_time_gran = 1000000000;
> +		s->cleancache_poolid = -1;
>  	}
>  out:
>  	return s;
> @@ -176,6 +178,11 @@ void deactivate_locked_super(struct supe
>  	struct file_system_type *fs = s->s_type;
>  	if (atomic_dec_and_test(&s->s_active)) {
>  		fs->kill_sb(s);
> +		if (s->cleancache_poolid >= 0) {
> +			int cleancache_poolid = s->cleancache_poolid;

That's a lot of characters for a local in a 3-line scope.

> +			s->cleancache_poolid = -1; /* avoid races */

Races with what?  Something else sneaking something into the pool after
the flush?  Is the filesystem dead at this stage or not?

> +			cleancache_flush_fs(cleancache_poolid);
> +		}
>  		put_filesystem(fs);
>  		put_super(s);
>  	} else {
> --- linux-2.6.36-rc3/fs/buffer.c	2010-08-29 09:36:04.000000000 -0600
> +++ linux-2.6.36-rc3-cleancache/fs/buffer.c	2010-08-30 09:20:42.000000000 -0600
> @@ -41,6 +41,7 @@
>  #include <linux/bitops.h>
>  #include <linux/mpage.h>
>  #include <linux/bit_spinlock.h>
> +#include <linux/cleancache.h>
>  
>  static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
>  
> @@ -277,6 +278,10 @@ void invalidate_bdev(struct block_device
>  	invalidate_bh_lrus();
>  	lru_add_drain_all();	/* make sure all lru add caches are flushed */
>  	invalidate_mapping_pages(mapping, 0, -1);
> +	/* 99% of the time, we don't need to flush the cleancache on the bdev.
> +	 * But, for the strange corners, lets be cautious
> +	 */

This comment-style is... unconventional for the kernel.

> +	cleancache_flush_inode(mapping);
>  }
>  EXPORT_SYMBOL(invalidate_bdev);
>  
> --- linux-2.6.36-rc3/fs/mpage.c	2010-08-29 09:36:04.000000000 -0600
> +++ linux-2.6.36-rc3-cleancache/fs/mpage.c	2010-08-30 09:20:43.000000000 -0600
> @@ -27,6 +27,7 @@
>  #include <linux/writeback.h>
>  #include <linux/backing-dev.h>
>  #include <linux/pagevec.h>
> +#include <linux/cleancache.h>
>  
>  /*
>   * I/O completion handler for multipage BIOs.
> @@ -286,6 +287,12 @@ do_mpage_readpage(struct bio *bio, struc
>  		SetPageMappedToDisk(page);
>  	}
>  
> +	if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
> +	    cleancache_get_page(page) == 0) {
> +		SetPageUptodate(page);
> +		goto confused;
> +	}
> +
>  	/*
>  	 * This page will go to BIO.  Do we need to send this BIO off first?
>  	 */
> --- linux-2.6.36-rc3/mm/filemap.c	2010-08-29 09:36:04.000000000 -0600
> +++ linux-2.6.36-rc3-cleancache/mm/filemap.c	2010-08-30 09:20:43.000000000 -0600
> @@ -34,6 +34,7 @@
>  #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
>  #include <linux/memcontrol.h>
>  #include <linux/mm_inline.h> /* for page_is_file_cache() */
> +#include <linux/cleancache.h>
>  #include "internal.h"
>  
>  /*
> @@ -119,6 +120,16 @@ void __remove_from_page_cache(struct pag
>  {
>  	struct address_space *mapping = page->mapping;
>  
> +	/*
> +	 * if we're uptodate, flush out into the cleancache, otherwise
> +	 * invalidate any existing cleancache entries.  We can't leave
> +	 * stale data around in the cleancache once our page is gone
> +	 */
> +	if (PageUptodate(page))
> +		cleancache_put_page(page);
> +	else
> +		cleancache_flush_page(mapping, page);
> +
>  	radix_tree_delete(&mapping->page_tree, page->index);
>  	page->mapping = NULL;
>  	mapping->nrpages--;
> --- linux-2.6.36-rc3/mm/truncate.c	2010-08-29 09:36:04.000000000 -0600
> +++ linux-2.6.36-rc3-cleancache/mm/truncate.c	2010-08-30 09:20:43.000000000 -0600
> @@ -19,6 +19,7 @@
>  #include <linux/task_io_accounting_ops.h>
>  #include <linux/buffer_head.h>	/* grr. try_to_release_page,
>  				   do_invalidatepage */
> +#include <linux/cleancache.h>
>  #include "internal.h"
>  
>  
> @@ -51,6 +52,7 @@ void do_invalidatepage(struct page *page
>  static inline void truncate_partial_page(struct page *page, unsigned partial)
>  {
>  	zero_user_segment(page, partial, PAGE_CACHE_SIZE);
> +	cleancache_flush_page(page->mapping, page);
>  	if (page_has_private(page))
>  		do_invalidatepage(page, partial);
>  }
> @@ -108,6 +110,10 @@ truncate_complete_page(struct address_sp
>  	clear_page_mlock(page);
>  	remove_from_page_cache(page);
>  	ClearPageMappedToDisk(page);
> +	/* this must be after the remove_from_page_cache which
> +	 * calls cleancache_put_page (and note page->mapping is now NULL)
> +	 */
> +	cleancache_flush_page(mapping, page);
>  	page_cache_release(page);	/* pagecache ref */
>  	return 0;
>  }
> @@ -215,6 +221,7 @@ void truncate_inode_pages_range(struct a
>  	pgoff_t next;
>  	int i;
>  
> +	cleancache_flush_inode(mapping);
>  	if (mapping->nrpages == 0)
>  		return;
>  
> @@ -290,6 +297,7 @@ void truncate_inode_pages_range(struct a
>  		pagevec_release(&pvec);
>  		mem_cgroup_uncharge_end();
>  	}
> +	cleancache_flush_inode(mapping);
>  }
>  EXPORT_SYMBOL(truncate_inode_pages_range);
>  
> @@ -428,6 +436,7 @@ int invalidate_inode_pages2_range(struct
>  	int did_range_unmap = 0;
>  	int wrapped = 0;
>  
> +	cleancache_flush_inode(mapping);
>  	pagevec_init(&pvec, 0);
>  	next = start;
>  	while (next <= end && !wrapped &&
> @@ -486,6 +495,7 @@ int invalidate_inode_pages2_range(struct
>  		mem_cgroup_uncharge_end();
>  		cond_resched();
>  	}
> +	cleancache_flush_inode(mapping);
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
>

   
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