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iomap: Support arbitrarily many blocks per page

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Size the uptodate array dynamically to support larger pages in the
page cache.  With a 64kB page, we're only saving 8 bytes per page today,
but with a 2MB maximum page size, we'd have to allocate more than 4kB
per page.  Add a few debugging assertions.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Matthew Wilcox (Oracle) 2020-09-21 08:58:40 -07:00 committed by Darrick J. Wong
parent b21866f514
commit 0a195b91e8
1 changed files with 17 additions and 5 deletions
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22
fs/iomap/buffered-io.c
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@ -22,18 +22,25 @@
#include "../internal.h"
/*
* Structure allocated for each page when block size < PAGE_SIZE to track
* sub-page uptodate status and I/O completions.
* Structure allocated for each page or THP 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)
{
/*
* per-block data is stored in the head page. Callers should
* not be dealing with tail pages (and if they are, they can
* call thp_head() first.
*/
VM_BUG_ON_PGFLAGS(PageTail(page), page);
if (page_has_private(page))
return (struct iomap_page *)page_private(page);
return NULL;
@ -45,11 +52,13 @@ 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 +68,14 @@ 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);
}