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Simplify and fix pad_wbuf

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A comment in the old code read:
        /* The math in this function can surely use some love */

And indeed it did.  In the case that area->a_used_bytes is exactly
4096 bytes below segment size it fell apart.  pad_wbuf is now split
into two helpers that are significantly less complicated.

Signed-off-by: Joern Engel <joern@logfs.org>
This commit is contained in:
Joern Engel 2010-03-28 12:47:09 +02:00
parent 1932191726
commit 81def6b986
1 changed files with 30 additions and 22 deletions
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52
fs/logfs/segment.c
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@ -93,49 +93,57 @@ void __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
} while (len);
}
/*
* bdev_writeseg will write full pages. Memset the tail to prevent data leaks.
*/
static void pad_wbuf(struct logfs_area *area, int final)
static void pad_partial_page(struct logfs_area *area)
{
struct super_block *sb = area->a_sb;
struct logfs_super *super = logfs_super(sb);
struct page *page;
u64 ofs = dev_ofs(sb, area->a_segno, area->a_used_bytes);
pgoff_t index = ofs >> PAGE_SHIFT;
long offset = ofs & (PAGE_SIZE-1);
u32 len = PAGE_SIZE - offset;
if (len == PAGE_SIZE) {
/* The math in this function can surely use some love */
len = 0;
}
if (len) {
BUG_ON(area->a_used_bytes >= super->s_segsize);
page = get_mapping_page(area->a_sb, index, 0);
if (len % PAGE_SIZE) {
page = get_mapping_page(sb, index, 0);
BUG_ON(!page); /* FIXME: reserve a pool */
memset(page_address(page) + offset, 0xff, len);
SetPagePrivate(page);
page_cache_release(page);
}
}
if (!final)
return;
static void pad_full_pages(struct logfs_area *area)
{
struct super_block *sb = area->a_sb;
struct logfs_super *super = logfs_super(sb);
u64 ofs = dev_ofs(sb, area->a_segno, area->a_used_bytes);
u32 len = super->s_segsize - area->a_used_bytes;
pgoff_t index = PAGE_CACHE_ALIGN(ofs) >> PAGE_CACHE_SHIFT;
pgoff_t no_indizes = len >> PAGE_CACHE_SHIFT;
struct page *page;
area->a_used_bytes += len;
for ( ; area->a_used_bytes < super->s_segsize;
area->a_used_bytes += PAGE_SIZE) {
/* Memset another page */
index++;
page = get_mapping_page(area->a_sb, index, 0);
while (no_indizes) {
page = get_mapping_page(sb, index, 0);
BUG_ON(!page); /* FIXME: reserve a pool */
memset(page_address(page), 0xff, PAGE_SIZE);
SetPageUptodate(page);
memset(page_address(page), 0xff, PAGE_CACHE_SIZE);
SetPagePrivate(page);
page_cache_release(page);
index++;
no_indizes--;
}
}
/*
* bdev_writeseg will write full pages. Memset the tail to prevent data leaks.
* Also make sure we allocate (and memset) all pages for final writeout.
*/
static void pad_wbuf(struct logfs_area *area, int final)
{
pad_partial_page(area);
if (final)
pad_full_pages(area);
}
/*
* We have to be careful with the alias tree. Since lookup is done by bix,
* it needs to be normalized, so 14, 15, 16, etc. all match when dealing with