diff mbox series

[v3,18/49] btrfs: extent_io: calculate inline extent buffer page size based on page size

Message ID 20200930015539.48867-19-wqu@suse.com
State New, archived
Headers show
Series btrfs: add partial rw support for subpage sector size | expand

Commit Message

Qu Wenruo Sept. 30, 2020, 1:55 a.m. UTC
Btrfs only support 64K as max node size, thus for 4K page system, we
would have at most 16 pages for one extent buffer.

For a system using 64K page size, we would really have just one
single page.

While we always use 16 pages for extent_buffer::pages[], this means for
systems using 64K pages, we are wasting memory for the 15 pages which
will never be utilized.

So this patch will change how the extent_buffer::pages[] array size is
calclulated, now it will be calculated using
BTRFS_MAX_METADATA_BLOCKSIZE and PAGE_SIZE.

For systems using 4K page size, it will stay 16 pages.
For systems using 64K page size, it will be just 1 page.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/extent_io.c | 6 +++---
 fs/btrfs/extent_io.h | 8 +++++---
 2 files changed, 8 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 6b925094608c..8662b27e42d6 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5024,9 +5024,9 @@  __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 	/*
 	 * Sanity checks, currently the maximum is 64k covered by 16x 4k pages
 	 */
-	BUILD_BUG_ON(BTRFS_MAX_METADATA_BLOCKSIZE
-		> MAX_INLINE_EXTENT_BUFFER_SIZE);
-	BUG_ON(len > MAX_INLINE_EXTENT_BUFFER_SIZE);
+	BUILD_BUG_ON(BTRFS_MAX_METADATA_BLOCKSIZE >
+		     INLINE_EXTENT_BUFFER_PAGES * PAGE_SIZE);
+	BUG_ON(len > BTRFS_MAX_METADATA_BLOCKSIZE);
 
 #ifdef CONFIG_BTRFS_DEBUG
 	eb->spinning_writers = 0;
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 3c9252b429e0..e588b3100ede 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -85,9 +85,11 @@  struct extent_io_ops {
 				    int mirror);
 };
 
-
-#define INLINE_EXTENT_BUFFER_PAGES 16
-#define MAX_INLINE_EXTENT_BUFFER_SIZE (INLINE_EXTENT_BUFFER_PAGES * PAGE_SIZE)
+/*
+ * The SZ_64K is BTRFS_MAX_METADATA_BLOCKSIZE, here just to avoid circle
+ * including "ctree.h".
+ */
+#define INLINE_EXTENT_BUFFER_PAGES (SZ_64K / PAGE_SIZE)
 struct extent_buffer {
 	u64 start;
 	unsigned long len;