#include <linux/pagemap.h>
#include <linux/blkdev.h>
#include <linux/genhd.h>
-#include <linux/bio.h>
#include <linux/buffer_head.h> /* for invalidate_bdev() */
#include <linux/backing-dev.h>
#include <linux/blkpg.h>
+#include <linux/writeback.h>
+
#include <asm/uaccess.h>
/* The RAM disk size is now a parameter */
* 2000 Transmeta Corp.
* aops copied from ramfs.
*/
-static int ramdisk_readpage(struct file *file, struct page *page)
-{
- if (!PageUptodate(page)) {
- void *kaddr = kmap_atomic(page, KM_USER0);
- memset(kaddr, 0, PAGE_CACHE_SIZE);
- flush_dcache_page(page);
- kunmap_atomic(kaddr, KM_USER0);
- SetPageUptodate(page);
+/*
+ * If a ramdisk page has buffers, some may be uptodate and some may be not.
+ * To bring the page uptodate we zero out the non-uptodate buffers. The
+ * page must be locked.
+ */
+static void make_page_uptodate(struct page *page)
+{
+ if (page_has_buffers(page)) {
+ struct buffer_head *bh = page_buffers(page);
+ struct buffer_head *head = bh;
+
+ do {
+ if (!buffer_uptodate(bh)) {
+ memset(bh->b_data, 0, bh->b_size);
+ /*
+ * akpm: I'm totally undecided about this. The
+ * buffer has just been magically brought "up to
+ * date", but nobody should want to be reading
+ * it anyway, because it hasn't been used for
+ * anything yet. It is still in a "not read
+ * from disk yet" state.
+ *
+ * But non-uptodate buffers against an uptodate
+ * page are against the rules. So do it anyway.
+ */
+ set_buffer_uptodate(bh);
+ }
+ } while ((bh = bh->b_this_page) != head);
+ } else {
+ memset(page_address(page), 0, PAGE_CACHE_SIZE);
}
+ flush_dcache_page(page);
+ SetPageUptodate(page);
+}
+
+static int ramdisk_readpage(struct file *file, struct page *page)
+{
+ if (!PageUptodate(page))
+ make_page_uptodate(page);
unlock_page(page);
return 0;
}
static int ramdisk_prepare_write(struct file *file, struct page *page,
unsigned offset, unsigned to)
{
- if (!PageUptodate(page)) {
- void *kaddr = kmap_atomic(page, KM_USER0);
-
- memset(kaddr, 0, PAGE_CACHE_SIZE);
- flush_dcache_page(page);
- kunmap_atomic(kaddr, KM_USER0);
- SetPageUptodate(page);
- }
- SetPageDirty(page);
+ if (!PageUptodate(page))
+ make_page_uptodate(page);
return 0;
}
static int ramdisk_commit_write(struct file *file, struct page *page,
unsigned offset, unsigned to)
{
+ set_page_dirty(page);
+ return 0;
+}
+
+/*
+ * ->writepage to the the blockdev's mapping has to redirty the page so that the
+ * VM doesn't go and steal it. We return WRITEPAGE_ACTIVATE so that the VM
+ * won't try to (pointlessly) write the page again for a while.
+ *
+ * Really, these pages should not be on the LRU at all.
+ */
+static int ramdisk_writepage(struct page *page, struct writeback_control *wbc)
+{
+ if (!PageUptodate(page))
+ make_page_uptodate(page);
+ SetPageDirty(page);
+ if (wbc->for_reclaim)
+ return WRITEPAGE_ACTIVATE;
+ unlock_page(page);
+ return 0;
+}
+
+/*
+ * This is a little speedup thing: short-circuit attempts to write back the
+ * ramdisk blockdev inode to its non-existent backing store.
+ */
+static int ramdisk_writepages(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ return 0;
+}
+
+/*
+ * ramdisk blockdev pages have their own ->set_page_dirty() because we don't
+ * want them to contribute to dirty memory accounting.
+ */
+static int ramdisk_set_page_dirty(struct page *page)
+{
+ SetPageDirty(page);
return 0;
}
static struct address_space_operations ramdisk_aops = {
- .readpage = ramdisk_readpage,
- .prepare_write = ramdisk_prepare_write,
- .commit_write = ramdisk_commit_write,
+ .readpage = ramdisk_readpage,
+ .prepare_write = ramdisk_prepare_write,
+ .commit_write = ramdisk_commit_write,
+ .writepage = ramdisk_writepage,
+ .set_page_dirty = ramdisk_set_page_dirty,
+ .writepages = ramdisk_writepages,
};
static int rd_blkdev_pagecache_IO(int rw, struct bio_vec *vec, sector_t sector,
struct address_space *mapping)
{
- unsigned long index = sector >> (PAGE_CACHE_SHIFT - 9);
+ pgoff_t index = sector >> (PAGE_CACHE_SHIFT - 9);
unsigned int vec_offset = vec->bv_offset;
int offset = (sector << 9) & ~PAGE_CACHE_MASK;
int size = vec->bv_len;
do {
int count;
- struct page * page;
- char * src, * dst;
- int unlock = 0;
+ struct page *page;
+ char *src;
+ char *dst;
count = PAGE_CACHE_SIZE - offset;
if (count > size)
count = size;
size -= count;
- page = find_get_page(mapping, index);
+ page = grab_cache_page(mapping, index);
if (!page) {
- page = grab_cache_page(mapping, index);
err = -ENOMEM;
- if (!page)
- goto out;
- err = 0;
-
- if (!PageUptodate(page)) {
- void *kaddr = kmap_atomic(page, KM_USER0);
-
- memset(kaddr, 0, PAGE_CACHE_SIZE);
- flush_dcache_page(page);
- kunmap_atomic(kaddr, KM_USER0);
- SetPageUptodate(page);
- }
-
- unlock = 1;
+ goto out;
}
+ if (!PageUptodate(page))
+ make_page_uptodate(page);
+
index++;
if (rw == READ) {
- src = kmap(page) + offset;
- dst = kmap(vec->bv_page) + vec_offset;
+ src = kmap_atomic(page, KM_USER0) + offset;
+ dst = kmap_atomic(vec->bv_page, KM_USER1) + vec_offset;
} else {
- dst = kmap(page) + offset;
- src = kmap(vec->bv_page) + vec_offset;
+ src = kmap_atomic(vec->bv_page, KM_USER0) + vec_offset;
+ dst = kmap_atomic(page, KM_USER1) + offset;
}
offset = 0;
vec_offset += count;
memcpy(dst, src, count);
- kunmap(page);
- kunmap(vec->bv_page);
+ kunmap_atomic(src, KM_USER0);
+ kunmap_atomic(dst, KM_USER1);
- if (rw == READ) {
+ if (rw == READ)
flush_dcache_page(vec->bv_page);
- } else {
- SetPageDirty(page);
- }
- if (unlock)
- unlock_page(page);
- __free_page(page);
+ else
+ set_page_dirty(page);
+ unlock_page(page);
+ put_page(page);
} while (size);
out:
struct block_device *bdev = inode->i_bdev;
if (cmd != BLKFLSBUF)
- return -EINVAL;
+ return -ENOTTY;
/*
* special: we want to release the ramdisk memory, it's not like with
return error;
}
+/*
+ * This is the backing_dev_info for the blockdev inode itself. It doesn't need
+ * writeback and it does not contribute to dirty memory accounting.
+ */
static struct backing_dev_info rd_backing_dev_info = {
.ra_pages = 0, /* No readahead */
.memory_backed = 1, /* Does not contribute to dirty memory */
- .unplug_io_fn = default_unplug_io_fn,
+ .unplug_io_fn = default_unplug_io_fn,
+};
+
+/*
+ * This is the backing_dev_info for the files which live atop the ramdisk
+ * "device". These files do need writeback and they do contribute to dirty
+ * memory accounting.
+ */
+static struct backing_dev_info rd_file_backing_dev_info = {
+ .ra_pages = 0, /* No readahead */
+ .memory_backed = 0, /* Does contribute to dirty memory */
+ .unplug_io_fn = default_unplug_io_fn,
};
static int rd_open(struct inode *inode, struct file *filp)
{
unsigned unit = iminor(inode);
- /*
- * Immunize device against invalidate_buffers() and prune_icache().
- */
if (rd_bdev[unit] == NULL) {
struct block_device *bdev = inode->i_bdev;
+ struct address_space *mapping;
+ int gfp_mask;
+
inode = igrab(bdev->bd_inode);
rd_bdev[unit] = bdev;
bdev->bd_openers++;
bdev->bd_block_size = rd_blocksize;
inode->i_size = get_capacity(rd_disks[unit])<<9;
- inode->i_mapping->a_ops = &ramdisk_aops;
- inode->i_mapping->backing_dev_info = &rd_backing_dev_info;
+ mapping = inode->i_mapping;
+ mapping->a_ops = &ramdisk_aops;
+ mapping->backing_dev_info = &rd_backing_dev_info;
+ bdev->bd_inode_backing_dev_info = &rd_file_backing_dev_info;
+
+ /*
+ * Deep badness. rd_blkdev_pagecache_IO() needs to allocate
+ * pagecache pages within a request_fn. We cannot recur back
+ * into the filesytem which is mounted atop the ramdisk, because
+ * that would deadlock on fs locks. And we really don't want
+ * to reenter rd_blkdev_pagecache_IO when we're already within
+ * that function.
+ *
+ * So we turn off __GFP_FS and __GFP_IO.
+ *
+ * And to give this thing a hope of working, turn on __GFP_HIGH.
+ * Hopefully, there's enough regular memory allocation going on
+ * for the page allocator emergency pools to keep the ramdisk
+ * driver happy.
+ */
+ gfp_mask = mapping_gfp_mask(mapping);
+ gfp_mask &= ~(__GFP_FS|__GFP_IO);
+ gfp_mask |= __GFP_HIGH;
+ mapping_set_gfp_mask(mapping, gfp_mask);
}
return 0;
git://git.onelab.eu / linux-2.6.git / blobdiff