omfs: add file routines

Add functions for reading and manipulating the storage of file data in
the extent-based OMFS.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/omfs/file.c b/fs/omfs/file.c
new file mode 100644 (file)
index 0000000..66e01fa
--- /dev/null
+++ b/fs/omfs/file.c
@@ -0,0 +1,346 @@
+/*
+ * OMFS (as used by RIO Karma) file operations.
+ * Copyright (C) 2005 Bob Copeland <me@bobcopeland.com>
+ * Released under GPL v2.
+ */
+
+#include <linux/version.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/mpage.h>
+#include "omfs.h"
+
+static int omfs_sync_file(struct file *file, struct dentry *dentry,
+               int datasync)
+{
+       struct inode *inode = dentry->d_inode;
+       int err;
+
+       err = sync_mapping_buffers(inode->i_mapping);
+       if (!(inode->i_state & I_DIRTY))
+               return err;
+       if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
+               return err;
+       err |= omfs_sync_inode(inode);
+       return err ? -EIO : 0;
+}
+
+void omfs_make_empty_table(struct buffer_head *bh, int offset)
+{
+       struct omfs_extent *oe = (struct omfs_extent *) &bh->b_data[offset];
+
+       oe->e_next = ~0ULL;
+       oe->e_extent_count = cpu_to_be32(1),
+       oe->e_fill = cpu_to_be32(0x22),
+       oe->e_entry.e_cluster = ~0ULL;
+       oe->e_entry.e_blocks = ~0ULL;
+}
+
+int omfs_shrink_inode(struct inode *inode)
+{
+       struct omfs_sb_info *sbi = OMFS_SB(inode->i_sb);
+       struct omfs_extent *oe;
+       struct omfs_extent_entry *entry;
+       struct buffer_head *bh;
+       u64 next, last;
+       u32 extent_count;
+       int ret;
+
+       /* traverse extent table, freeing each entry that is greater
+        * than inode->i_size;
+        */
+       next = inode->i_ino;
+
+       /* only support truncate -> 0 for now */
+       ret = -EIO;
+       if (inode->i_size != 0)
+               goto out;
+
+       bh = sb_bread(inode->i_sb, clus_to_blk(sbi, next));
+       if (!bh)
+               goto out;
+
+       oe = (struct omfs_extent *)(&bh->b_data[OMFS_EXTENT_START]);
+
+       for (;;) {
+
+               if (omfs_is_bad(sbi, (struct omfs_header *) bh->b_data, next)) {
+                       brelse(bh);
+                       goto out;
+               }
+
+               extent_count = be32_to_cpu(oe->e_extent_count);
+               last = next;
+               next = be64_to_cpu(oe->e_next);
+               entry = &oe->e_entry;
+
+               /* ignore last entry as it is the terminator */
+               for (; extent_count > 1; extent_count--) {
+                       u64 start, count;
+                       start = be64_to_cpu(entry->e_cluster);
+                       count = be64_to_cpu(entry->e_blocks);
+
+                       omfs_clear_range(inode->i_sb, start, (int) count);
+                       entry++;
+               }
+               omfs_make_empty_table(bh, (char *) oe - bh->b_data);
+               mark_buffer_dirty(bh);
+               brelse(bh);
+
+               if (last != inode->i_ino)
+                       omfs_clear_range(inode->i_sb, last, sbi->s_mirrors);
+
+               if (next == ~0)
+                       break;
+
+               bh = sb_bread(inode->i_sb, clus_to_blk(sbi, next));
+               if (!bh)
+                       goto out;
+               oe = (struct omfs_extent *) (&bh->b_data[OMFS_EXTENT_CONT]);
+       }
+       ret = 0;
+out:
+       return ret;
+}
+
+static void omfs_truncate(struct inode *inode)
+{
+       omfs_shrink_inode(inode);
+       mark_inode_dirty(inode);
+}
+
+/*
+ * Add new blocks to the current extent, or create new entries/continuations
+ * as necessary.
+ */
+static int omfs_grow_extent(struct inode *inode, struct omfs_extent *oe,
+                       u64 *ret_block)
+{
+       struct omfs_extent_entry *terminator;
+       struct omfs_extent_entry *entry = &oe->e_entry;
+       struct omfs_sb_info *sbi = OMFS_SB(inode->i_sb);
+       u32 extent_count = be32_to_cpu(oe->e_extent_count);
+       u64 new_block = 0;
+       u32 max_count;
+       int new_count;
+       int ret = 0;
+
+       /* reached the end of the extent table with no blocks mapped.
+        * there are three possibilities for adding: grow last extent,
+        * add a new extent to the current extent table, and add a
+        * continuation inode.  in last two cases need an allocator for
+        * sbi->s_cluster_size
+        */
+
+       /* TODO: handle holes */
+
+       /* should always have a terminator */
+       if (extent_count < 1)
+               return -EIO;
+
+       /* trivially grow current extent, if next block is not taken */
+       terminator = entry + extent_count - 1;
+       if (extent_count > 1) {
+               entry = terminator-1;
+               new_block = be64_to_cpu(entry->e_cluster) +
+                       be64_to_cpu(entry->e_blocks);
+
+               if (omfs_allocate_block(inode->i_sb, new_block)) {
+                       entry->e_blocks =
+                               cpu_to_be64(be64_to_cpu(entry->e_blocks) + 1);
+                       terminator->e_blocks = ~(cpu_to_be64(
+                               be64_to_cpu(~terminator->e_blocks) + 1));
+                       goto out;
+               }
+       }
+       max_count = (sbi->s_sys_blocksize - OMFS_EXTENT_START -
+               sizeof(struct omfs_extent)) /
+               sizeof(struct omfs_extent_entry) + 1;
+
+       /* TODO: add a continuation block here */
+       if (be32_to_cpu(oe->e_extent_count) > max_count-1)
+               return -EIO;
+
+       /* try to allocate a new cluster */
+       ret = omfs_allocate_range(inode->i_sb, 1, sbi->s_clustersize,
+               &new_block, &new_count);
+       if (ret)
+               goto out_fail;
+
+       /* copy terminator down an entry */
+       entry = terminator;
+       terminator++;
+       memcpy(terminator, entry, sizeof(struct omfs_extent_entry));
+
+       entry->e_cluster = cpu_to_be64(new_block);
+       entry->e_blocks = cpu_to_be64((u64) new_count);
+
+       terminator->e_blocks = ~(cpu_to_be64(
+               be64_to_cpu(~terminator->e_blocks) + (u64) new_count));
+
+       /* write in new entry */
+       oe->e_extent_count = cpu_to_be32(1 + be32_to_cpu(oe->e_extent_count));
+
+out:
+       *ret_block = new_block;
+out_fail:
+       return ret;
+}
+
+/*
+ * Scans across the directory table for a given file block number.
+ * If block not found, return 0.
+ */
+static sector_t find_block(struct inode *inode, struct omfs_extent_entry *ent,
+                       sector_t block, int count, int *left)
+{
+       /* count > 1 because of terminator */
+       sector_t searched = 0;
+       for (; count > 1; count--) {
+               int numblocks = clus_to_blk(OMFS_SB(inode->i_sb),
+                       be64_to_cpu(ent->e_blocks));
+
+               if (block >= searched  &&
+                   block < searched + numblocks) {
+                       /*
+                        * found it at cluster + (block - searched)
+                        * numblocks - (block - searched) is remainder
+                        */
+                       *left = numblocks - (block - searched);
+                       return clus_to_blk(OMFS_SB(inode->i_sb),
+                               be64_to_cpu(ent->e_cluster)) +
+                               block - searched;
+               }
+               searched += numblocks;
+               ent++;
+       }
+       return 0;
+}
+
+static int omfs_get_block(struct inode *inode, sector_t block,
+                         struct buffer_head *bh_result, int create)
+{
+       struct buffer_head *bh;
+       sector_t next, offset;
+       int ret;
+       u64 new_block;
+       int extent_count;
+       struct omfs_extent *oe;
+       struct omfs_extent_entry *entry;
+       struct omfs_sb_info *sbi = OMFS_SB(inode->i_sb);
+       int max_blocks = bh_result->b_size >> inode->i_blkbits;
+       int remain;
+
+       ret = -EIO;
+       bh = sb_bread(inode->i_sb, clus_to_blk(sbi, inode->i_ino));
+       if (!bh)
+               goto out;
+
+       oe = (struct omfs_extent *)(&bh->b_data[OMFS_EXTENT_START]);
+       next = inode->i_ino;
+
+       for (;;) {
+
+               if (omfs_is_bad(sbi, (struct omfs_header *) bh->b_data, next))
+                       goto out_brelse;
+
+               extent_count = be32_to_cpu(oe->e_extent_count);
+               next = be64_to_cpu(oe->e_next);
+               entry = &oe->e_entry;
+
+               offset = find_block(inode, entry, block, extent_count, &remain);
+               if (offset > 0) {
+                       ret = 0;
+                       map_bh(bh_result, inode->i_sb, offset);
+                       if (remain > max_blocks)
+                               remain = max_blocks;
+                       bh_result->b_size = (remain << inode->i_blkbits);
+                       goto out_brelse;
+               }
+               if (next == ~0)
+                       break;
+
+               brelse(bh);
+               bh = sb_bread(inode->i_sb, clus_to_blk(sbi, next));
+               if (!bh)
+                       goto out;
+               oe = (struct omfs_extent *) (&bh->b_data[OMFS_EXTENT_CONT]);
+       }
+       if (create) {
+               ret = omfs_grow_extent(inode, oe, &new_block);
+               if (ret == 0) {
+                       mark_buffer_dirty(bh);
+                       mark_inode_dirty(inode);
+                       map_bh(bh_result, inode->i_sb,
+                                       clus_to_blk(sbi, new_block));
+               }
+       }
+out_brelse:
+       brelse(bh);
+out:
+       return ret;
+}
+
+static int omfs_readpage(struct file *file, struct page *page)
+{
+       return block_read_full_page(page, omfs_get_block);
+}
+
+static int omfs_readpages(struct file *file, struct address_space *mapping,
+               struct list_head *pages, unsigned nr_pages)
+{
+       return mpage_readpages(mapping, pages, nr_pages, omfs_get_block);
+}
+
+static int omfs_writepage(struct page *page, struct writeback_control *wbc)
+{
+       return block_write_full_page(page, omfs_get_block, wbc);
+}
+
+static int
+omfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
+{
+       return mpage_writepages(mapping, wbc, omfs_get_block);
+}
+
+static int omfs_write_begin(struct file *file, struct address_space *mapping,
+                       loff_t pos, unsigned len, unsigned flags,
+                       struct page **pagep, void **fsdata)
+{
+       *pagep = NULL;
+       return block_write_begin(file, mapping, pos, len, flags,
+                               pagep, fsdata, omfs_get_block);
+}
+
+static sector_t omfs_bmap(struct address_space *mapping, sector_t block)
+{
+       return generic_block_bmap(mapping, block, omfs_get_block);
+}
+
+struct file_operations omfs_file_operations = {
+       .llseek = generic_file_llseek,
+       .read = do_sync_read,
+       .write = do_sync_write,
+       .aio_read = generic_file_aio_read,
+       .aio_write = generic_file_aio_write,
+       .mmap = generic_file_mmap,
+       .fsync = omfs_sync_file,
+       .splice_read = generic_file_splice_read,
+};
+
+struct inode_operations omfs_file_inops = {
+       .truncate = omfs_truncate
+};
+
+struct address_space_operations omfs_aops = {
+       .readpage = omfs_readpage,
+       .readpages = omfs_readpages,
+       .writepage = omfs_writepage,
+       .writepages = omfs_writepages,
+       .sync_page = block_sync_page,
+       .write_begin = omfs_write_begin,
+       .write_end = generic_write_end,
+       .bmap = omfs_bmap,
+};
+