Messages in this thread Patch in this message | | | Subject | [PATCH 09/10] afs: Alter dirty range encoding in page->private | From | David Howells <> | Date | Tue, 27 Oct 2020 13:51:01 +0000 |
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Currently, page->private on an afs page is used to store the range of dirtied data within the page, where the range includes the lower bound, but excludes the upper bound (e.g. 0-1 is a range covering a single byte).
This, however, requires a superfluous bit for the last-byte bound so that on a 4KiB page, it can say 0-4096 to indicate the whole page, the idea being that having both numbers the same would indicate an empty range. This is unnecessary as the PG_private bit is clear if it's an empty range (as is PG_dirty).
Alter the way the dirty range is encoded in page->private such that the upper bound is reduced by 1 (e.g. 0-0 is then specified the same single byte range mentioned above).
Applying this to both bounds frees up two bits, one of which can be used in a future commit.
Signed-off-by: David Howells <dhowells@redhat.com> ---
fs/afs/internal.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/afs/internal.h b/fs/afs/internal.h index acefa6bf0a4d..0ff1088a7c87 100644 --- a/fs/afs/internal.h +++ b/fs/afs/internal.h @@ -878,12 +878,12 @@ static inline unsigned int afs_page_dirty_from(unsigned long priv) static inline unsigned int afs_page_dirty_to(unsigned long priv) { - return (priv >> __AFS_PAGE_PRIV_SHIFT) & __AFS_PAGE_PRIV_MASK; + return ((priv >> __AFS_PAGE_PRIV_SHIFT) & __AFS_PAGE_PRIV_MASK) + 1; } static inline unsigned long afs_page_dirty(unsigned int from, unsigned int to) { - return ((unsigned long)to << __AFS_PAGE_PRIV_SHIFT) | from; + return ((unsigned long)(to - 1) << __AFS_PAGE_PRIV_SHIFT) | from; } #include <trace/events/afs.h>
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