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[PATCH 14/18] xfs: kill xfs_buf_btoc

To: xfs@xxxxxxxxxxx
Subject: [PATCH 14/18] xfs: kill xfs_buf_btoc
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 13 Apr 2012 22:10:57 +1000
In-reply-to: <1334319061-12968-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1334319061-12968-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

xfs_buf_btoc and friends are simple macros that do basic block
to page index conversion and vice versa. These aren't widely used,
and we use open coded masking and shifting everywhere else. Hence
remove themacros and open code the work they do.

Also, use of PAGE_CACHE_{SIZE|SHIFT|MASK} for these macros is now
incorrect - we are using pages directly and not the page cache, so
use PAGE_{SIZE|MASK|SHIFT} instead.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>
---
 fs/xfs/xfs_buf.c |   39 +++++++++++++++++++++------------------
 fs/xfs/xfs_buf.h |    5 -----
 2 files changed, 21 insertions(+), 23 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index b508eaf..7a945fd 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -300,7 +300,7 @@ xfs_buf_allocate_memory(
        size_t                  nbytes, offset;
        gfp_t                   gfp_mask = xb_to_gfp(flags);
        unsigned short          page_count, i;
-       xfs_off_t               end;
+       xfs_off_t               start, end;
        int                     error;
 
        /*
@@ -308,15 +308,15 @@ xfs_buf_allocate_memory(
         * the memory from the heap - there's no need for the complexity of
         * page arrays to keep allocation down to order 0.
         */
-       if (bp->b_length < BTOBB(PAGE_SIZE)) {
-               bp->b_addr = kmem_alloc(BBTOB(bp->b_length), xb_to_km(flags));
+       size = BBTOB(bp->b_length);
+       if (size < PAGE_SIZE) {
+               bp->b_addr = kmem_alloc(size, xb_to_km(flags));
                if (!bp->b_addr) {
                        /* low memory - use alloc_page loop instead */
                        goto use_alloc_page;
                }
 
-               if (((unsigned long)(bp->b_addr + BBTOB(bp->b_length) - 1) &
-                                                               PAGE_MASK) !=
+               if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
                    ((unsigned long)bp->b_addr & PAGE_MASK)) {
                        /* b_addr spans two pages - use alloc_page instead */
                        kmem_free(bp->b_addr);
@@ -332,14 +332,14 @@ xfs_buf_allocate_memory(
        }
 
 use_alloc_page:
-       end = BBTOB(bp->b_bn + bp->b_length);
-       page_count = xfs_buf_btoc(end) - xfs_buf_btoct(BBTOB(bp->b_bn));
+       start = BBTOB(bp->b_bn) >> PAGE_SHIFT;
+       end = (BBTOB(bp->b_bn + bp->b_length) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+       page_count = end - start;
        error = _xfs_buf_get_pages(bp, page_count, flags);
        if (unlikely(error))
                return error;
 
        offset = bp->b_offset;
-       size = BBTOB(bp->b_length);
        bp->b_flags |= _XBF_PAGES;
 
        for (i = 0; i < bp->b_page_count; i++) {
@@ -1314,27 +1314,30 @@ xfs_buf_iomove(
        void                    *data,  /* data address                 */
        xfs_buf_rw_t            mode)   /* read/write/zero flag         */
 {
-       size_t                  bend, cpoff, csize;
-       struct page             *page;
+       size_t                  bend;
 
        bend = boff + bsize;
        while (boff < bend) {
-               page = bp->b_pages[xfs_buf_btoct(boff + bp->b_offset)];
-               cpoff = xfs_buf_poff(boff + bp->b_offset);
-               csize = min_t(size_t,
-                             PAGE_SIZE - cpoff, BBTOB(bp->b_io_length) - boff);
+               struct page     *page;
+               int             page_index, page_offset, csize;
+
+               page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
+               page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
+               page = bp->b_pages[page_index];
+               csize = min_t(size_t, PAGE_SIZE - page_offset,
+                                     BBTOB(bp->b_io_length) - boff);
 
-               ASSERT(((csize + cpoff) <= PAGE_SIZE));
+               ASSERT((csize + page_offset) <= PAGE_SIZE);
 
                switch (mode) {
                case XBRW_ZERO:
-                       memset(page_address(page) + cpoff, 0, csize);
+                       memset(page_address(page) + page_offset, 0, csize);
                        break;
                case XBRW_READ:
-                       memcpy(data, page_address(page) + cpoff, csize);
+                       memcpy(data, page_address(page) + page_offset, csize);
                        break;
                case XBRW_WRITE:
-                       memcpy(page_address(page) + cpoff, data, csize);
+                       memcpy(page_address(page) + page_offset, data, csize);
                }
 
                boff += csize;
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 9787645..5b048f7 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -32,11 +32,6 @@
 
 #define XFS_BUF_DADDR_NULL     ((xfs_daddr_t) (-1LL))
 
-#define xfs_buf_ctob(pp)       ((pp) * PAGE_CACHE_SIZE)
-#define xfs_buf_btoc(dd)       (((dd) + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT)
-#define xfs_buf_btoct(dd)      ((dd) >> PAGE_CACHE_SHIFT)
-#define xfs_buf_poff(aa)       ((aa) & ~PAGE_CACHE_MASK)
-
 typedef enum {
        XBRW_READ = 1,                  /* transfer into target memory */
        XBRW_WRITE = 2,                 /* transfer from target memory */
-- 
1.7.9.5

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