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authorJoern Engel <joern@wh.fh-wedel.de>2007-02-20 20:22:22 +0100
committerJoern Engel <joern@wh.fh-wedel.de>2007-02-20 20:22:22 +0100
commit21d31f1f7c8f832324fb55eb4b1397b16258904e (patch)
tree54dfa7f24f601713261160e578abeaa5c66a2652 /drivers/mtd
parent8870530a4053add56a2c0eb90a3669facb9f7117 (diff)
[PATCH] [MTD] block2mtd: remove readahead code
Over the years there was a slow trickle of complaints against the readahead code. Most of them concerned performance, Peter Zijlstra stumbled over it when working unrelated changes and I believe there was an actual bug report. Oh, Andrew Morton also complained about duplicating code from mm/readahead.c. It is just not worth it. On flash media like usb sticks, readahead will make things go slow - very slow. On spinning disks, readahead may be a win, but this is definitely not the place to add it. Signed-off-by: Jörn Engel <joern@lazybastard.org>
Diffstat (limited to 'drivers/mtd')
-rw-r--r--drivers/mtd/devices/block2mtd.c57
1 files changed, 4 insertions, 53 deletions
diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c
index 3bc92153e2b..ce47544dc12 100644
--- a/drivers/mtd/devices/block2mtd.c
+++ b/drivers/mtd/devices/block2mtd.c
@@ -40,56 +40,9 @@ struct block2mtd_dev {
static LIST_HEAD(blkmtd_device_list);
-#define PAGE_READAHEAD 64
-static void cache_readahead(struct address_space *mapping, int index)
+static struct page* page_read(struct address_space *mapping, int index)
{
filler_t *filler = (filler_t*)mapping->a_ops->readpage;
- int i, pagei;
- unsigned ret = 0;
- unsigned long end_index;
- struct page *page;
- LIST_HEAD(page_pool);
- struct inode *inode = mapping->host;
- loff_t isize = i_size_read(inode);
-
- if (!isize) {
- INFO("iSize=0 in cache_readahead\n");
- return;
- }
-
- end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);
-
- read_lock_irq(&mapping->tree_lock);
- for (i = 0; i < PAGE_READAHEAD; i++) {
- pagei = index + i;
- if (pagei > end_index) {
- INFO("Overrun end of disk in cache readahead\n");
- break;
- }
- page = radix_tree_lookup(&mapping->page_tree, pagei);
- if (page && (!i))
- break;
- if (page)
- continue;
- read_unlock_irq(&mapping->tree_lock);
- page = page_cache_alloc_cold(mapping);
- read_lock_irq(&mapping->tree_lock);
- if (!page)
- break;
- page->index = pagei;
- list_add(&page->lru, &page_pool);
- ret++;
- }
- read_unlock_irq(&mapping->tree_lock);
- if (ret)
- read_cache_pages(mapping, &page_pool, filler, NULL);
-}
-
-
-static struct page* page_readahead(struct address_space *mapping, int index)
-{
- filler_t *filler = (filler_t*)mapping->a_ops->readpage;
- cache_readahead(mapping, index);
return read_cache_page(mapping, index, filler, NULL);
}
@@ -105,7 +58,7 @@ static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
u_long *max;
while (pages) {
- page = page_readahead(mapping, index);
+ page = page_read(mapping, index);
if (!page)
return -ENOMEM;
if (IS_ERR(page))
@@ -174,8 +127,7 @@ static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
cpylen = len; // this page
len = len - cpylen;
- // Get page
- page = page_readahead(dev->blkdev->bd_inode->i_mapping, index);
+ page = page_read(dev->blkdev->bd_inode->i_mapping, index);
if (!page)
return -ENOMEM;
if (IS_ERR(page))
@@ -213,8 +165,7 @@ static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
cpylen = len; // this page
len = len - cpylen;
- // Get page
- page = page_readahead(mapping, index);
+ page = page_read(mapping, index);
if (!page)
return -ENOMEM;
if (IS_ERR(page))