[PATCH 07/14] FS-Cache: Provide a filesystem-specific sync'able page bit [try #8]

From: David Howells
Date: Wed May 10 2006 - 12:03:28 EST

The attached patch provides a filesystem-specific page bit that a filesystem
can synchronise upon. This can be used, for example, by a netfs to synchronise
with CacheFS writing its pages to disk.

The PG_checked bit is replaced with PG_fs_misc, and various operations are
provided based upon that. The *PageChecked() macros still exist, though now
they just convert to *PageFsMisc() macros. The name of the "checked" macros
seems appropriate as they're used for metadata page validation by various
filesystems.

Signed-Off-By: David Howells <dhowells@xxxxxxxxxx>
---

fs/afs/dir.c | 5 +----
fs/ext2/dir.c | 6 +++---
fs/ext3/inode.c | 10 +++++-----
fs/freevxfs/vxfs_subr.c | 2 +-
fs/reiserfs/inode.c | 10 +++++-----
include/linux/page-flags.h | 15 ++++++++++-----
include/linux/pagemap.h | 11 +++++++++++
mm/filemap.c | 17 +++++++++++++++++
mm/migrate.c | 4 ++--
mm/page_alloc.c | 2 +-
10 files changed, 56 insertions(+), 26 deletions(-)

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index a6dff6a..c23de2b 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -155,11 +155,9 @@ #endif
}
}

- SetPageChecked(page);
return;

error:
- SetPageChecked(page);
SetPageError(page);

} /* end afs_dir_check_page() */
@@ -193,8 +191,7 @@ static struct page *afs_dir_get_page(str
kmap(page);
if (!PageUptodate(page))
goto fail;
- if (!PageChecked(page))
- afs_dir_check_page(dir, page);
+ afs_dir_check_page(dir, page);
if (PageError(page))
goto fail;
}
diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index d672aa9..cf9cee4 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -112,7 +112,7 @@ static void ext2_check_page(struct page
if (offs != limit)
goto Eend;
out:
- SetPageChecked(page);
+ SetPageFsMisc(page);
return;

/* Too bad, we had an error */
@@ -152,7 +152,7 @@ Eend:
dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs,
(unsigned long) le32_to_cpu(p->inode));
fail:
- SetPageChecked(page);
+ SetPageFsMisc(page);
SetPageError(page);
}

@@ -166,7 +166,7 @@ static struct page * ext2_get_page(struc
kmap(page);
if (!PageUptodate(page))
goto fail;
- if (!PageChecked(page))
+ if (!PageFsMisc(page))
ext2_check_page(page);
if (PageError(page))
goto fail;
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 2edd7ee..2a38eee 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -1528,12 +1528,12 @@ static int ext3_journalled_writepage(str
goto no_write;
}

- if (!page_has_buffers(page) || PageChecked(page)) {
+ if (!page_has_buffers(page) || PageFsMisc(page)) {
/*
* It's mmapped pagecache. Add buffers and journal it. There
* doesn't seem much point in redirtying the page here.
*/
- ClearPageChecked(page);
+ ClearPageFsMisc(page);
ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE,
ext3_get_block);
if (ret != 0) {
@@ -1590,7 +1590,7 @@ static void ext3_invalidatepage(struct p
* If it's a full truncate we just forget about the pending dirtying
*/
if (offset == 0)
- ClearPageChecked(page);
+ ClearPageFsMisc(page);

journal_invalidatepage(journal, page, offset);
}
@@ -1599,7 +1599,7 @@ static int ext3_releasepage(struct page
{
journal_t *journal = EXT3_JOURNAL(page->mapping->host);

- WARN_ON(PageChecked(page));
+ WARN_ON(PageFsMisc(page));
if (!page_has_buffers(page))
return 0;
return journal_try_to_free_buffers(journal, page, wait);
@@ -1695,7 +1695,7 @@ out:
*/
static int ext3_journalled_set_page_dirty(struct page *page)
{
- SetPageChecked(page);
+ SetPageFsMisc(page);
return __set_page_dirty_nobuffers(page);
}

diff --git a/fs/freevxfs/vxfs_subr.c b/fs/freevxfs/vxfs_subr.c
index 50aae77..e884bfc 100644
--- a/fs/freevxfs/vxfs_subr.c
+++ b/fs/freevxfs/vxfs_subr.c
@@ -79,7 +79,7 @@ vxfs_get_page(struct address_space *mapp
kmap(pp);
if (!PageUptodate(pp))
goto fail;
- /** if (!PageChecked(pp)) **/
+ /** if (!PageFsMisc(pp)) **/
/** vxfs_check_page(pp); **/
if (PageError(pp))
goto fail;
diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index 9857e50..3c79e02 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -2352,7 +2352,7 @@ static int reiserfs_write_full_page(stru
struct buffer_head *head, *bh;
int partial = 0;
int nr = 0;
- int checked = PageChecked(page);
+ int checked = PageFsMisc(page);
struct reiserfs_transaction_handle th;
struct super_block *s = inode->i_sb;
int bh_per_page = PAGE_CACHE_SIZE / s->s_blocksize;
@@ -2421,7 +2421,7 @@ static int reiserfs_write_full_page(stru
* blocks we're going to log
*/
if (checked) {
- ClearPageChecked(page);
+ ClearPageFsMisc(page);
reiserfs_write_lock(s);
error = journal_begin(&th, s, bh_per_page + 1);
if (error) {
@@ -2802,7 +2802,7 @@ static void reiserfs_invalidatepage(stru
BUG_ON(!PageLocked(page));

if (offset == 0)
- ClearPageChecked(page);
+ ClearPageFsMisc(page);

if (!page_has_buffers(page))
goto out;
@@ -2843,7 +2843,7 @@ static int reiserfs_set_page_dirty(struc
{
struct inode *inode = page->mapping->host;
if (reiserfs_file_data_log(inode)) {
- SetPageChecked(page);
+ SetPageFsMisc(page);
return __set_page_dirty_nobuffers(page);
}
return __set_page_dirty_buffers(page);
@@ -2866,7 +2866,7 @@ static int reiserfs_releasepage(struct p
struct buffer_head *bh;
int ret = 1;

- WARN_ON(PageChecked(page));
+ WARN_ON(PageFsMisc(page));
spin_lock(&j->j_dirty_buffers_lock);
head = page_buffers(page);
bh = head;
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index d276a4e..7d7ef97 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -73,7 +73,7 @@ #define PG_lru 5
#define PG_active 6
#define PG_slab 7 /* slab debug (Suparna wants this) */

-#define PG_checked 8 /* kill me in 2.5.<early>. */
+#define PG_fs_misc 8
#define PG_arch_1 9
#define PG_reserved 10
#define PG_private 11 /* Has something at ->private */
@@ -274,10 +274,6 @@ #else
#define PageHighMem(page) 0 /* needed to optimize away at compile time */
#endif

-#define PageChecked(page) test_bit(PG_checked, &(page)->flags)
-#define SetPageChecked(page) set_bit(PG_checked, &(page)->flags)
-#define ClearPageChecked(page) clear_bit(PG_checked, &(page)->flags)
-
#define PageReserved(page) test_bit(PG_reserved, &(page)->flags)
#define SetPageReserved(page) set_bit(PG_reserved, &(page)->flags)
#define ClearPageReserved(page) clear_bit(PG_reserved, &(page)->flags)
@@ -376,4 +372,13 @@ static inline void set_page_writeback(st
test_set_page_writeback(page);
}

+/*
+ * Filesystem-specific page bit testing
+ */
+#define PageFsMisc(page) test_bit(PG_fs_misc, &(page)->flags)
+#define SetPageFsMisc(page) set_bit(PG_fs_misc, &(page)->flags)
+#define TestSetPageFsMisc(page) test_and_set_bit(PG_fs_misc, &(page)->flags)
+#define ClearPageFsMisc(page) clear_bit(PG_fs_misc, &(page)->flags)
+#define TestClearPageFsMisc(page) test_and_clear_bit(PG_fs_misc, &(page)->flags)
+
#endif /* PAGE_FLAGS_H */
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 7a1af57..049382d 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -208,6 +208,17 @@ static inline void wait_on_page_writebac
extern void end_page_writeback(struct page *page);

/*
+ * Wait for filesystem-specific page synchronisation to complete
+ */
+static inline void wait_on_page_fs_misc(struct page *page)
+{
+ if (PageFsMisc(page))
+ wait_on_page_bit(page, PG_fs_misc);
+}
+
+extern void fastcall end_page_fs_misc(struct page *page);
+
+/*
* Fault a userspace page into pagetables. Return non-zero on a fault.
*
* This assumes that two userspace pages are always sufficient. That's
diff --git a/mm/filemap.c b/mm/filemap.c
index fd57442..02c4925 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -545,6 +545,23 @@ void fastcall __lock_page(struct page *p
EXPORT_SYMBOL(__lock_page);

/*
+ * Note completion of filesystem specific page synchronisation
+ *
+ * This is used to allow a page to be written to a filesystem cache in the
+ * background without holding up the completion of readpage
+ */
+void fastcall end_page_fs_misc(struct page *page)
+{
+ smp_mb__before_clear_bit();
+ if (!TestClearPageFsMisc(page))
+ BUG();
+ smp_mb__after_clear_bit();
+ __wake_up_bit(page_waitqueue(page), &page->flags, PG_fs_misc);
+}
+
+EXPORT_SYMBOL(end_page_fs_misc);
+
+/*
* a rather lightweight function, finding and getting a reference to a
* hashed page atomically.
*/
diff --git a/mm/migrate.c b/mm/migrate.c
index 1c25040..bb3f22f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -272,8 +272,8 @@ void migrate_page_copy(struct page *newp
SetPageUptodate(newpage);
if (PageActive(page))
SetPageActive(newpage);
- if (PageChecked(page))
- SetPageChecked(newpage);
+ if (PageFsMisc(page))
+ SetPageFsMisc(newpage);
if (PageMappedToDisk(page))
SetPageMappedToDisk(newpage);

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ea77c99..b40e04a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -544,7 +544,7 @@ static int prep_new_page(struct page *pa

page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
1 << PG_referenced | 1 << PG_arch_1 |
- 1 << PG_checked | 1 << PG_mappedtodisk);
+ 1 << PG_fs_misc | 1 << PG_mappedtodisk);
set_page_private(page, 0);
set_page_refcounted(page);
kernel_map_pages(page, 1 << order, 1);

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