[PATCH 3/17] [LogFS] dev_bdev.c

Joern Engel
2009-11-20T20:22:26Z

---
fs/logfs/dev_bdev.c | 263 ++++

diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
new file mode 100644
index 0000000..58a057b
--- /dev/null
+++ b/fs/logfs/dev_bdev.c
@@ -0,0 +1,263 @@
+/*
+ * fs/logfs/dev_bdev.c - Device access methods for block devices
+ *
+ * As should be obvious for Linux kernel code, license is GPLv2
+ *
+ * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
+ */
+#include "logfs.h"
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>
+
+#define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
+
+static void request_complete(struct bio *bio, int err)
+{
+ complete((struct completion *)bio->bi_private);
+}
+
+static int sync_request(struct page *page, struct block_device *bdev, int rw)
+{
+ struct bio bio;
+ struct bio_vec bio_vec;
+ struct completion complete;
+
+ bio_init(&bio);
+ bio.bi_io_vec = &bio_vec;
+ bio_vec.bv_page = page;
+ bio_vec.bv_len = PAGE_SIZE;
+ bio_vec.bv_offset = 0;
+ bio.bi_vcnt = 1;
+ bio.bi_idx = 0;
+ bio.bi_size = PAGE_SIZE;
+ bio.bi_bdev = bdev;
+ bio.bi_sector = page->index * (PAGE_SIZE >> 9);
+ init_completion(&complete);
+ bio.bi_private = &complete;
+ bio.bi_end_io = request_complete;
+
+ submit_bio(rw, &bio);
+ generic_unplug_device(bdev_get_queue(bdev));
+ wait_for_completion(&complete);
+ return test_bit(BIO_UPTODATE, &bio.bi_flags) ? 0 : -EIO;
+}
+
+static int bdev_readpage(void *_sb, struct page *page)
+{
+ struct super_block *sb = _sb;
+ struct block_device *bdev = logfs_super(sb)->s_bdev;
+ int err;
+
+ err = sync_request(page, bdev, READ);
+ if (err) {
+ ClearPageUptodate(page);
+ SetPageError(page);
+ } else {
+ SetPageUptodate(page);
+ ClearPageError(page);
+ }
+ unlock_page(page);
+ return err;
+}
+
+static DECLARE_WAIT_QUEUE_HEAD(wq);
+
+static void writeseg_end_io(struct bio *bio, int err)
+{
+ const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+ struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+ struct super_block *sb = bio->bi_private;
+ struct logfs_super *super = logfs_super(sb);
+ struct page *page;
+
+ BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
+ BUG_ON(err);
+ BUG_ON(bio->bi_vcnt == 0);
+ do {
+ page = bvec->bv_page;
+ if (--bvec >= bio->bi_io_vec)
+ prefetchw(&bvec->bv_page->flags);
+
+ end_page_writeback(page);
+ } while (bvec >= bio->bi_io_vec);
+ bio_put(bio);
+ if (atomic_dec_and_test(&super->s_pending_writes))
+ wake_up(&wq);
+}
+
+static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
+ size_t nr_pages)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct address_space *mapping = super->s_mapping_inode->i_mapping;
+ struct bio *bio;
+ struct page *page;
+ struct request_queue *q = bdev_get_queue(sb->s_bdev);
+ unsigned int max_pages = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9);
+ int i;
+
+ bio = bio_alloc(GFP_NOFS, max_pages);
+ BUG_ON(!bio); /* FIXME: handle this */
+
+ for (i = 0; i < nr_pages; i++) {
+ if (i >= max_pages) {
+ /* Block layer cannot split bios :( */
+ bio->bi_vcnt = i;
+ bio->bi_idx = 0;
+ bio->bi_size = i * PAGE_SIZE;
+ bio->bi_bdev = super->s_bdev;
+ bio->bi_sector = ofs >> 9;
+ bio->bi_private = sb;
+ bio->bi_end_io = writeseg_end_io;
+ atomic_inc(&super->s_pending_writes);
+ submit_bio(WRITE, bio);
+
+ ofs += i * PAGE_SIZE;
+ index += i;
+ nr_pages -= i;
+ i = 0;
+
+ bio = bio_alloc(GFP_NOFS, max_pages);
+ BUG_ON(!bio);
+ }
+ page = find_lock_page(mapping, index + i);
+ BUG_ON(!page);
+ bio->bi_io_vec[i].bv_page = page;
+ bio->bi_io_vec[i].bv_len = PAGE_SIZE;
+ bio->bi_io_vec[i].bv_offset = 0;
+
+ BUG_ON(PageWriteback(page));
+ set_page_writeback(page);
+ unlock_page(page);
+ }
+ bio->bi_vcnt = nr_pages;
+ bio->bi_idx = 0;
+ bio->bi_size = nr_pages * PAGE_SIZE;
+ bio->bi_bdev = super->s_bdev;
+ bio->bi_sector = ofs >> 9;
+ bio->bi_private = sb;
+ bio->bi_end_io = writeseg_end_io;
+ atomic_inc(&super->s_pending_writes);
+ submit_bio(WRITE, bio);
+ return 0;
+}
+
+static void bdev_writeseg(struct super_block *sb, u64 ofs, size_t len)
+{
+ struct logfs_super *super = logfs_super(sb);
+ int head;
+
+ BUG_ON(super->s_flags & LOGFS_SB_FLAG_RO);
+
+ if (len == 0) {
+ /* This can happen when the object fit perfectly into a
+ * segment, the segment gets written per sync and subsequently
+ * closed.
+ */
+ return;
+ }
+ head = ofs & (PAGE_SIZE - 1);
+ if (head) {
+ ofs -= head;
+ len += head;
+ }
+ len = PAGE_ALIGN(len);
+ __bdev_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
+ generic_unplug_device(bdev_get_queue(logfs_super(sb)->s_bdev));
+}
+
+static int bdev_erase(struct super_block *sb, loff_t to, size_t len)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct address_space *mapping = super->s_mapping_inode->i_mapping;
+ struct page *page;
+ pgoff_t index = to >> PAGE_SHIFT;
+ int i, nr_pages = len >> PAGE_SHIFT;
+
+ BUG_ON(to & (PAGE_SIZE - 1));
+ BUG_ON(len & (PAGE_SIZE - 1));
+
+ if (logfs_super(sb)->s_flags & LOGFS_SB_FLAG_RO)
+ return -EROFS;
+
+ for (i = 0; i < nr_pages; i++) {
+ page = find_get_page(mapping, index + i);
+ if (page) {
+ memset(page_address(page), 0xFF, PAGE_SIZE);
+ page_cache_release(page);
+ }
+ }
+ return 0;
+}
+
+static void bdev_sync(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+
+ wait_event(wq, atomic_read(&super->s_pending_writes) == 0);
+}
+
+static struct page *bdev_find_first_sb(struct super_block *sb, u64 *ofs)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct address_space *mapping = super->s_mapping_inode->i_mapping;
+ filler_t *filler = bdev_readpage;
+
+ *ofs = 0;
+ return read_cache_page(mapping, 0, filler, sb);
+}
+
+static struct page *bdev_find_last_sb(struct super_block *sb, u64 *ofs)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct address_space *mapping = super->s_mapping_inode->i_mapping;
+ filler_t *filler = bdev_readpage;
+ u64 pos = (super->s_bdev->bd_inode->i_size & ~0xfffULL) - 0x1000;
+ pgoff_t index = pos >> PAGE_SHIFT;
+
+ *ofs = pos;
+ return read_cache_page(mapping, index, filler, sb);
+}
+
+static int bdev_write_sb(struct super_block *sb, struct page *page)
+{
+ struct block_device *bdev = logfs_super(sb)->s_bdev;
+
+ /* Nothing special to do for block devices. */
+ return sync_request(page, bdev, WRITE);
+}
+
+static void bdev_put_device(struct super_block *sb)
+{
+ close_bdev_exclusive(logfs_super(sb)->s_bdev, FMODE_READ|FMODE_WRITE);
+}
+
+static const struct logfs_device_ops bd_devops = {
+ .find_first_sb = bdev_find_first_sb,
+ .find_last_sb = bdev_find_last_sb,
+ .write_sb = bdev_write_sb,
+ .readpage = bdev_readpage,
+ .writeseg = bdev_writeseg,
+ .erase = bdev_erase,
+ .sync = bdev_sync,
+ .put_device = bdev_put_device,
+};
+
+int logfs_get_sb_bdev(struct file_system_type *type, int flags,
+ const char *devname, struct vfsmount *mnt)
+{
+ struct block_device *bdev;
+
+ bdev = open_bdev_exclusive(devname, FMODE_READ|FMODE_WRITE, type);
+ if (IS_ERR(bdev))
+ return PTR_ERR(bdev);
+
+ if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
+ int mtdnr = MINOR(bdev->bd_dev);
+ close_bdev_exclusive(bdev, FMODE_READ|FMODE_WRITE);
+ return logfs_get_sb_mtd(type, flags, mtdnr, mnt);
+ }
+
+ return logfs_get_sb_device(type, flags, NULL, bdev, &bd_devops, mnt);
+}