ocfs2: Implement llseek()

ocfs2 implements its own llseek() to provide the SEEK_HOLE/SEEK_DATA
functionality.

SEEK_HOLE sets the file pointer to the start of either a hole or an unwritten
(preallocated) extent, that is greater than or equal to the supplied offset.

SEEK_DATA sets the file pointer to the start of an allocated extent (not
unwritten) that is greater than or equal to the supplied offset.

If the supplied offset is on a desired region, then the file pointer is set
to it. Offsets greater than or equal to the file size return -ENXIO.

Unwritten (preallocated) extents are considered holes because the file system
treats reads to such regions in the same way as it does to holes.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>

1 files changed, 53 insertions, 2 deletions

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 0fc2bd34039d..c0f015e11c28 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2591,6 +2591,57 @@ bail:
         return ret;
 }
 
+/* Refer generic_file_llseek_unlocked() */
+static loff_t ocfs2_file_llseek(struct file *file, loff_t offset, int origin)
+{
+        struct inode *inode = file->f_mapping->host;
+        int ret = 0;
+
+        mutex_lock(&inode->i_mutex);
+
+        switch (origin) {
+        case SEEK_SET:
+                break;
+        case SEEK_END:
+                offset += inode->i_size;
+                break;
+        case SEEK_CUR:
+                if (offset == 0) {
+                        offset = file->f_pos;
+                        goto out;
+                }
+                offset += file->f_pos;
+                break;
+        case SEEK_DATA:
+        case SEEK_HOLE:
+                ret = ocfs2_seek_data_hole_offset(file, &offset, origin);
+                if (ret)
+                        goto out;
+                break;
+        default:
+                ret = -EINVAL;
+                goto out;
+        }
+
+        if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET))
+                ret = -EINVAL;
+        if (!ret && offset > inode->i_sb->s_maxbytes)
+                ret = -EINVAL;
+        if (ret)
+                goto out;
+
+        if (offset != file->f_pos) {
+                file->f_pos = offset;
+                file->f_version = 0;
+        }
+
+out:
+        mutex_unlock(&inode->i_mutex);
+        if (ret)
+                return ret;
+        return offset;
+}
+
 const struct inode_operations ocfs2_file_iops = {
         .setattr        = ocfs2_setattr,
         .getattr        = ocfs2_getattr,
@@ -2615,7 +2666,7 @@ const struct inode_operations ocfs2_special_file_iops = {
  * ocfs2_fops_no_plocks and ocfs2_dops_no_plocks!
  */
 const struct file_operations ocfs2_fops = {
-        .llseek         = generic_file_llseek,
+        .llseek         = ocfs2_file_llseek,
         .read           = do_sync_read,
         .write          = do_sync_write,
         .mmap           = ocfs2_mmap,
@@ -2663,7 +2714,7 @@ const struct file_operations ocfs2_dops = {
  * the cluster.
  */
 const struct file_operations ocfs2_fops_no_plocks = {
-        .llseek         = generic_file_llseek,
+        .llseek         = ocfs2_file_llseek,
         .read           = do_sync_read,
         .write          = do_sync_write,
         .mmap           = ocfs2_mmap,