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

Jeremy Fitzhardinge
2010-08-30T22:51:33Z

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@oracle.com>
> Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
>
> 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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