[PATCH 4/17] [LogFS] dev_mtd.c

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

---
fs/logfs/dev_mtd.c | 253 ++++

diff --git a/fs/logfs/dev_mtd.c b/fs/logfs/dev_mtd.c
new file mode 100644
index 0000000..68e99d0
--- /dev/null
+++ b/fs/logfs/dev_mtd.c
@@ -0,0 +1,253 @@
+/*
+ * fs/logfs/dev_mtd.c - Device access methods for MTD
+ *
+ * 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/completion.h>
+#include <linux/mount.h>
+#include <linux/sched.h>
+
+#define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
+
+static int mtd_read(struct super_block *sb, loff_t ofs, size_t len, void *buf)
+{
+ struct mtd_info *mtd = logfs_super(sb)->s_mtd;
+ size_t retlen;
+ int ret;
+
+ ret = mtd->read(mtd, ofs, len, &retlen, buf);
+ BUG_ON(ret == -EINVAL);
+ if (ret)
+ return ret;
+
+ /* Not sure if we should loop instead. */
+ if (retlen != len)
+ return -EIO;
+
+ return 0;
+}
+
+static int mtd_write(struct super_block *sb, loff_t ofs, size_t len, void *buf)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct mtd_info *mtd = super->s_mtd;
+ size_t retlen;
+ loff_t page_start, page_end;
+ int ret;
+
+ if (super->s_flags & LOGFS_SB_FLAG_RO)
+ return -EROFS;
+
+ BUG_ON((ofs >= mtd->size) || (len > mtd->size - ofs));
+ BUG_ON(ofs != (ofs >> super->s_writeshift) << super->s_writeshift);
+ BUG_ON(len > PAGE_CACHE_SIZE);
+ page_start = ofs & PAGE_CACHE_MASK;
+ page_end = PAGE_CACHE_ALIGN(ofs + len) - 1;
+ ret = mtd->write(mtd, ofs, len, &retlen, buf);
+ if (ret || (retlen != len))
+ return -EIO;
+
+ return 0;
+}
+
+/*
+ * For as long as I can remember (since about 2001) mtd->erase has been an
+ * asynchronous interface lacking the first driver to actually use the
+ * asynchronous properties. So just to prevent the first implementor of such
+ * a thing from breaking logfs in 2350, we do the usual pointless dance to
+ * declare a completion variable and wait for completion before returning
+ * from mtd_erase(). What an excercise in futility!
+ */
+static void logfs_erase_callback(struct erase_info *ei)
+{
+ complete((struct completion *)ei->priv);
+}
+
+static int mtd_erase_mapping(struct super_block *sb, loff_t ofs, 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 = ofs >> PAGE_SHIFT;
+
+ for (index = ofs >> PAGE_SHIFT; index < (ofs + len) >> PAGE_SHIFT; index++) {
+ page = find_get_page(mapping, index);
+ if (!page)
+ continue;
+ memset(page_address(page), 0xFF, PAGE_SIZE);
+ page_cache_release(page);
+ }
+ return 0;
+}
+
+static int mtd_erase(struct super_block *sb, loff_t ofs, size_t len)
+{
+ struct mtd_info *mtd = logfs_super(sb)->s_mtd;
+ struct erase_info ei;
+ DECLARE_COMPLETION_ONSTACK(complete);
+ int ret;
+
+ BUG_ON(len % mtd->erasesize);
+ if (logfs_super(sb)->s_flags & LOGFS_SB_FLAG_RO)
+ return -EROFS;
+
+ memset(&ei, 0, sizeof(ei));
+ ei.mtd = mtd;
+ ei.addr = ofs;
+ ei.len = len;
+ ei.callback = logfs_erase_callback;
+ ei.priv = (long)&complete;
+ ret = mtd->erase(mtd, &ei);
+ if (ret)
+ return -EIO;
+
+ wait_for_completion(&complete);
+ if (ei.state != MTD_ERASE_DONE)
+ return -EIO;
+ return mtd_erase_mapping(sb, ofs, len);
+}
+
+static void mtd_sync(struct super_block *sb)
+{
+ struct mtd_info *mtd = logfs_super(sb)->s_mtd;
+
+ if (mtd->sync)
+ mtd->sync(mtd);
+}
+
+static int mtd_readpage(void *_sb, struct page *page)
+{
+ struct super_block *sb = _sb;
+ int err;
+
+ err = mtd_read(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
+ page_address(page));
+ if (err == -EUCLEAN) {
+ err = 0;
+ /* FIXME: force GC this segment */
+ }
+ if (err) {
+ ClearPageUptodate(page);
+ SetPageError(page);
+ } else {
+ SetPageUptodate(page);
+ ClearPageError(page);
+ }
+ unlock_page(page);
+ return err;
+}
+
+static struct page *mtd_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 = mtd_readpage;
+ struct mtd_info *mtd = super->s_mtd;
+
+ if (!mtd->block_isbad)
+ return NULL;
+
+ *ofs = 0;
+ while (mtd->block_isbad(mtd, *ofs)) {
+ *ofs += mtd->erasesize;
+ if (*ofs >= mtd->size)
+ return NULL;
+ }
+ BUG_ON(*ofs & ~PAGE_MASK);
+ return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
+}
+
+static struct page *mtd_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 = mtd_readpage;
+ struct mtd_info *mtd = super->s_mtd;
+
+ if (!mtd->block_isbad)
+ return NULL;
+
+ *ofs = mtd->size - mtd->erasesize;
+ while (mtd->block_isbad(mtd, *ofs)) {
+ *ofs -= mtd->erasesize;
+ if (*ofs <= 0)
+ return NULL;
+ }
+ *ofs = *ofs + mtd->erasesize - 0x1000;
+ BUG_ON(*ofs & ~PAGE_MASK);
+ return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
+}
+
+static int __mtd_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 page *page;
+ int i, err;
+
+ for (i = 0; i < nr_pages; i++) {
+ page = find_lock_page(mapping, index + i);
+ BUG_ON(!page);
+
+ err = mtd_write(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
+ page_address(page));
+ unlock_page(page);
+ page_cache_release(page);
+ if (err)
+ return err;
+ }
+ return 0;
+}
+
+static void mtd_writeseg(struct super_block *sb, u64 ofs, size_t len)
+{
+ struct logfs_super *super = logfs_super(sb);
+ int head;
+
+ if (super->s_flags & LOGFS_SB_FLAG_RO)
+ return;
+
+ 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);
+ __mtd_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
+}
+
+static void mtd_put_device(struct super_block *sb)
+{
+ put_mtd_device(logfs_super(sb)->s_mtd);
+}
+
+static const struct logfs_device_ops mtd_devops = {
+ .find_first_sb = mtd_find_first_sb,
+ .find_last_sb = mtd_find_last_sb,
+ .readpage = mtd_readpage,
+ .writeseg = mtd_writeseg,
+ .erase = mtd_erase,
+ .sync = mtd_sync,
+ .put_device = mtd_put_device,
+};
+
+int logfs_get_sb_mtd(struct file_system_type *type, int flags,
+ int mtdnr, struct vfsmount *mnt)
+{
+ struct mtd_info *mtd;
+ const struct logfs_device_ops *devops = &mtd_devops;
+
+ mtd = get_mtd_device(NULL, mtdnr);
+ return logfs_get_sb_device(type, flags, mtd, NULL, devops, mnt);
+}