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Message-ID: <20070317003617.GB17362@lst.de>
Date: Sat, 17 Mar 2007 01:36:17 +0100
From: Christoph Hellwig <hch@....de>
To: Timothy Shimmin <tes@....com>
Cc: Christoph Hellwig <hch@....de>, xfs@....sgi.com,
ecashin@...aid.com, akpm@...l.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] xfs: stop using kmalloc in xfs_buf_get_noaddr
> It looks like you might need: for (i--; i >= 0; i--)
> (or: for (j = 0; j < i; j++) etc.)
>
> Because if the initial alloc_page loop goes to completion then:
> i == pagecount
> and if alloc_page loop terminates early then
> bp->b_pages[i] == NULL
> So we have gone 1 too far in both cases and need to
> start free'ing back one.
> Unless I missed something.
No, I was missing something :)
Here's the updated version:
Index: linux-2.6/fs/xfs/linux-2.6/xfs_buf.c
===================================================================
--- linux-2.6.orig/fs/xfs/linux-2.6/xfs_buf.c 2007-03-16 15:32:20.000000000 +0100
+++ linux-2.6/fs/xfs/linux-2.6/xfs_buf.c 2007-03-16 15:35:10.000000000 +0100
@@ -314,7 +314,7 @@ xfs_buf_free(
ASSERT(list_empty(&bp->b_hash_list));
- if (bp->b_flags & _XBF_PAGE_CACHE) {
+ if (bp->b_flags & (_XBF_PAGE_CACHE|_XBF_PAGES)) {
uint i;
if ((bp->b_flags & XBF_MAPPED) && (bp->b_page_count > 1))
@@ -323,18 +323,11 @@ xfs_buf_free(
for (i = 0; i < bp->b_page_count; i++) {
struct page *page = bp->b_pages[i];
- ASSERT(!PagePrivate(page));
+ if (bp->b_flags & _XBF_PAGE_CACHE)
+ ASSERT(!PagePrivate(page));
page_cache_release(page);
}
_xfs_buf_free_pages(bp);
- } else if (bp->b_flags & _XBF_KMEM_ALLOC) {
- /*
- * XXX(hch): bp->b_count_desired might be incorrect (see
- * xfs_buf_associate_memory for details), but fortunately
- * the Linux version of kmem_free ignores the len argument..
- */
- kmem_free(bp->b_addr, bp->b_count_desired);
- _xfs_buf_free_pages(bp);
}
xfs_buf_deallocate(bp);
@@ -764,41 +757,41 @@ xfs_buf_get_noaddr(
size_t len,
xfs_buftarg_t *target)
{
- size_t malloc_len = len;
+ unsigned long page_count = PAGE_ALIGN(len) >> PAGE_SHIFT;
+ int error, i;
xfs_buf_t *bp;
- void *data;
- int error;
bp = xfs_buf_allocate(0);
if (unlikely(bp == NULL))
goto fail;
_xfs_buf_initialize(bp, target, 0, len, 0);
- try_again:
- data = kmem_alloc(malloc_len, KM_SLEEP | KM_MAYFAIL | KM_LARGE);
- if (unlikely(data == NULL))
+ error = _xfs_buf_get_pages(bp, page_count, 0);
+ if (error)
goto fail_free_buf;
- /* check whether alignment matches.. */
- if ((__psunsigned_t)data !=
- ((__psunsigned_t)data & ~target->bt_smask)) {
- /* .. else double the size and try again */
- kmem_free(data, malloc_len);
- malloc_len <<= 1;
- goto try_again;
- }
-
- error = xfs_buf_associate_memory(bp, data, len);
- if (error)
+ for (i = 0; i < page_count; i++) {
+ bp->b_pages[i] = alloc_page(GFP_KERNEL);
+ if (!bp->b_pages[i])
+ goto fail_free_mem;
+ }
+ bp->b_flags |= _XBF_PAGES;
+
+ error = _xfs_buf_map_pages(bp, XBF_MAPPED);
+ if (unlikely(error)) {
+ printk(KERN_WARNING "%s: failed to map pages\n",
+ __FUNCTION__);
goto fail_free_mem;
- bp->b_flags |= _XBF_KMEM_ALLOC;
+ }
xfs_buf_unlock(bp);
XB_TRACE(bp, "no_daddr", data);
return bp;
+
fail_free_mem:
- kmem_free(data, malloc_len);
+ while (--i >= 0)
+ __free_page(bp->b_pages[i]);
fail_free_buf:
xfs_buf_free(bp);
fail:
Index: linux-2.6/fs/xfs/linux-2.6/xfs_buf.h
===================================================================
--- linux-2.6.orig/fs/xfs/linux-2.6/xfs_buf.h 2007-03-13 18:18:05.000000000 +0100
+++ linux-2.6/fs/xfs/linux-2.6/xfs_buf.h 2007-03-16 15:34:20.000000000 +0100
@@ -63,7 +63,7 @@ typedef enum {
/* flags used only internally */
_XBF_PAGE_CACHE = (1 << 17),/* backed by pagecache */
- _XBF_KMEM_ALLOC = (1 << 18),/* backed by kmem_alloc() */
+ _XBF_PAGES = (1 << 18), /* backed by refcounted pages */
_XBF_RUN_QUEUES = (1 << 19),/* run block device task queue */
_XBF_DELWRI_Q = (1 << 21), /* buffer on delwri queue */
} xfs_buf_flags_t;
-
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