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author | Joern Engel <joern@wh.fh-wedel.de> | 2007-02-20 20:22:22 +0100 |
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committer | Joern Engel <joern@wh.fh-wedel.de> | 2007-02-20 20:22:22 +0100 |
commit | 21d31f1f7c8f832324fb55eb4b1397b16258904e (patch) | |
tree | 54dfa7f24f601713261160e578abeaa5c66a2652 /drivers/mtd | |
parent | 8870530a4053add56a2c0eb90a3669facb9f7117 (diff) | |
download | kernel_samsung_smdk4412-21d31f1f7c8f832324fb55eb4b1397b16258904e.zip kernel_samsung_smdk4412-21d31f1f7c8f832324fb55eb4b1397b16258904e.tar.gz kernel_samsung_smdk4412-21d31f1f7c8f832324fb55eb4b1397b16258904e.tar.bz2 |
[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.c | 57 |
1 files changed, 4 insertions, 53 deletions
diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c index 3bc9215..ce47544 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)) |