ocfs2: Wrap virtual block reads in ocfs2_read_virt_blocks()

The ocfs2_read_dir_block() function really maps an inode's virtual
blocks to physical ones before calling ocfs2_read_blocks().  Let's
extract that to common code, because other places might want to do that.

Other than the block number being virtual, ocfs2_read_virt_blocks()
takes the same arguments as ocfs2_read_blocks().  It converts those
virtual block numbers to physical before calling ocfs2_read_blocks()
directly.  If the blocks asked for are discontiguous, this can mean
multiple calls to ocfs2_read_blocks(), but this is mostly hidden from
the caller.

Like ocfs2_read_blocks(), the caller can pass in an existing
buffer_head.  This is usually done to pick up some readahead I/O.
ocfs2_read_virt_blocks() checks the buffer_head's block number
against the extent map - it must match.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index 0bd9d9698a24..f2bb1a04d253 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -806,3 +806,74 @@ out:
 
         return ret;
 }
+
+int ocfs2_read_virt_blocks(struct inode *inode, u64 v_block, int nr,
+                           struct buffer_head *bhs[], int flags,
+                           int (*validate)(struct super_block *sb,
+                                           struct buffer_head *bh))
+{
+        int rc = 0;
+        u64 p_block, p_count;
+        int i, count, done = 0;
+
+        mlog_entry("(inode = %p, v_block = %llu, nr = %d, bhs = %p, "
+                   "flags = %x, validate = %p)\n",
+                   inode, (unsigned long long)v_block, nr, bhs, flags,
+                   validate);
+
+        if (((v_block + nr - 1) << inode->i_sb->s_blocksize_bits) >=
+            i_size_read(inode)) {
+                BUG_ON(!(flags & OCFS2_BH_READAHEAD));
+                goto out;
+        }
+
+        while (done < nr) {
+                down_read(&OCFS2_I(inode)->ip_alloc_sem);
+                rc = ocfs2_extent_map_get_blocks(inode, v_block + done,
+                                                 &p_block, &p_count, NULL);
+                up_read(&OCFS2_I(inode)->ip_alloc_sem);
+                if (rc) {
+                        mlog_errno(rc);
+                        break;
+                }
+
+                if (!p_block) {
+                        rc = -EIO;
+                        mlog(ML_ERROR,
+                             "Inode #%llu contains a hole at offset %llu\n",
+                             (unsigned long long)OCFS2_I(inode)->ip_blkno,
+                             (unsigned long long)(v_block + done) <<
+                             inode->i_sb->s_blocksize_bits);
+                        break;
+                }
+
+                count = nr - done;
+                if (p_count < count)
+                        count = p_count;
+
+                /*
+                 * If the caller passed us bhs, they should have come
+                 * from a previous readahead call to this function.  Thus,
+                 * they should have the right b_blocknr.
+                 */
+                for (i = 0; i < count; i++) {
+                        if (!bhs[done + i])
+                                continue;
+                        BUG_ON(bhs[done + i]->b_blocknr != (p_block + i));
+                }
+
+                rc = ocfs2_read_blocks(inode, p_block, count, bhs + done,
+                                       flags, validate);
+                if (rc) {
+                        mlog_errno(rc);
+                        break;
+                }
+                done += count;
+        }
+
+out:
+        mlog_exit(rc);
+        return rc;
+}
+
+