From: Dave Chinner <dchinner@xxxxxxxxxx>
Based on a patch from Christoph Hellwig.
This splits out the heap allocation and page allocation portions of
the buffer memory allocation into two separate helper functions.
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/xfs_buf.c | 126 ++++++++++++++++++++++++++++-------------------
1 file changed, 74 insertions(+), 52 deletions(-)
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 592800c8852f..2e35d344a69b 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -347,65 +347,55 @@ xfs_buf_free(
kmem_cache_free(xfs_buf_zone, bp);
}
-/*
- * Allocates all the pages for buffer in question and builds it's page list.
- */
-STATIC int
-xfs_buf_allocate_memory(
- struct xfs_buf *bp,
- uint flags)
+static int
+xfs_buf_alloc_kmem(
+ struct xfs_buf *bp,
+ size_t size,
+ xfs_buf_flags_t flags)
{
- size_t size;
- size_t nbytes, offset;
- gfp_t gfp_mask = xb_to_gfp(flags);
- unsigned short page_count, i;
- xfs_off_t start, end;
- int error;
- xfs_km_flags_t kmflag_mask = 0;
+ int align_mask = xfs_buftarg_dma_alignment(bp->b_target);
+ xfs_km_flags_t kmflag_mask = KM_NOFS;
- /*
- * assure zeroed buffer for non-read cases.
- */
- if (!(flags & XBF_READ)) {
+ /* Assure zeroed buffer for non-read cases. */
+ if (!(flags & XBF_READ))
kmflag_mask |= KM_ZERO;
- gfp_mask |= __GFP_ZERO;
- }
- /*
- * for buffers that are contained within a single page, just allocate
- * the memory from the heap - there's no need for the complexity of
- * page arrays to keep allocation down to order 0.
- */
- size = BBTOB(bp->b_length);
- if (size < PAGE_SIZE) {
- int align_mask = xfs_buftarg_dma_alignment(bp->b_target);
- bp->b_addr = kmem_alloc_io(size, align_mask,
- KM_NOFS | kmflag_mask);
- if (!bp->b_addr) {
- /* low memory - use alloc_page loop instead */
- goto use_alloc_page;
- }
+ bp->b_addr = kmem_alloc_io(size, align_mask, kmflag_mask);
+ if (!bp->b_addr)
+ return -ENOMEM;
- 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);
- bp->b_addr = NULL;
- goto use_alloc_page;
- }
- bp->b_offset = offset_in_page(bp->b_addr);
- bp->b_pages = bp->b_page_array;
- bp->b_pages[0] = kmem_to_page(bp->b_addr);
- bp->b_page_count = 1;
- bp->b_flags |= _XBF_KMEM;
- return 0;
+ 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);
+ bp->b_addr = NULL;
+ return -ENOMEM;
}
+ bp->b_offset = offset_in_page(bp->b_addr);
+ bp->b_pages = bp->b_page_array;
+ bp->b_pages[0] = kmem_to_page(bp->b_addr);
+ bp->b_page_count = 1;
+ bp->b_flags |= _XBF_KMEM;
+ return 0;
+}
+
+static int
+xfs_buf_alloc_pages(
+ struct xfs_buf *bp,
+ uint page_count,
+ xfs_buf_flags_t flags)
+{
+ gfp_t gfp_mask = xb_to_gfp(flags);
+ size_t size;
+ size_t offset;
+ size_t nbytes;
+ int i;
+ int error;
+
+ /* Assure zeroed buffer for non-read cases. */
+ if (!(flags & XBF_READ))
+ gfp_mask |= __GFP_ZERO;
-use_alloc_page:
- start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
- end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
- >> PAGE_SHIFT;
- page_count = end - start;
error = _xfs_buf_get_pages(bp, page_count);
if (unlikely(error))
return error;
@@ -458,6 +448,38 @@ xfs_buf_allocate_memory(
return error;
}
+
+/*
+ * Allocates all the pages for buffer in question and builds it's page list.
+ */
+static int
+xfs_buf_allocate_memory(
+ struct xfs_buf *bp,
+ uint flags)
+{
+ size_t size;
+ xfs_off_t start, end;
+ int error;
+
+ /*
+ * For buffers that fit entirely within a single page, first attempt to
+ * allocate the memory from the heap to minimise memory usage. If we
+ * can't get heap memory for these small buffers, we fall back to using
+ * the page allocator.
+ */
+ size = BBTOB(bp->b_length);
+ if (size < PAGE_SIZE) {
+ error = xfs_buf_alloc_kmem(bp, size, flags);
+ if (!error)
+ return 0;
+ }
+
+ start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
+ end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
+ >> PAGE_SHIFT;
+ return xfs_buf_alloc_pages(bp, end - start, flags);
+}
+
/*
* Map buffer into kernel address-space if necessary.
*/
--
2.31.1
