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Subject[PATCH 3/3] iomap: Support arbitrarily many blocks per page
Date
Size the uptodate array dynamically and add a few debugging assertions.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/iomap/buffered-io.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index dbf9572dabe9..844e95cacea8 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -22,18 +22,19 @@
#include "../internal.h"

/*
- * Structure allocated for each page when block size < PAGE_SIZE to track
+ * Structure allocated for each page when block size < page size to track
* sub-page uptodate status and I/O completions.
*/
struct iomap_page {
atomic_t read_count;
atomic_t write_count;
spinlock_t uptodate_lock;
- DECLARE_BITMAP(uptodate, PAGE_SIZE / 512);
+ unsigned long uptodate[];
};

static inline struct iomap_page *to_iomap_page(struct page *page)
{
+ VM_BUG_ON_PGFLAGS(PageTail(page), page);
if (page_has_private(page))
return (struct iomap_page *)page_private(page);
return NULL;
@@ -45,11 +46,13 @@ static struct iomap_page *
iomap_page_create(struct inode *inode, struct page *page)
{
struct iomap_page *iop = to_iomap_page(page);
+ unsigned int nr_blocks = i_blocks_per_page(inode, page);

- if (iop || i_blocks_per_page(inode, page) <= 1)
+ if (iop || nr_blocks <= 1)
return iop;

- iop = kzalloc(sizeof(*iop), GFP_NOFS | __GFP_NOFAIL);
+ iop = kzalloc(struct_size(iop, uptodate, BITS_TO_LONGS(nr_blocks)),
+ GFP_NOFS | __GFP_NOFAIL);
spin_lock_init(&iop->uptodate_lock);
attach_page_private(page, iop);
return iop;
@@ -59,11 +62,14 @@ static void
iomap_page_release(struct page *page)
{
struct iomap_page *iop = detach_page_private(page);
+ unsigned int nr_blocks = i_blocks_per_page(page->mapping->host, page);

if (!iop)
return;
WARN_ON_ONCE(atomic_read(&iop->read_count));
WARN_ON_ONCE(atomic_read(&iop->write_count));
+ WARN_ON_ONCE(bitmap_full(iop->uptodate, nr_blocks) !=
+ PageUptodate(page));
kfree(iop);
}

--
2.28.0
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