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>
diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index 23457b4..2f5b92e 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -832,6 +832,102 @@
return ret;
}
+int ocfs2_seek_data_hole_offset(struct file *file, loff_t *offset, int origin)
+{
+ struct inode *inode = file->f_mapping->host;
+ int ret;
+ unsigned int is_last = 0, is_data = 0;
+ u16 cs_bits = OCFS2_SB(inode->i_sb)->s_clustersize_bits;
+ u32 cpos, cend, clen, hole_size;
+ u64 extoff, extlen;
+ struct buffer_head *di_bh = NULL;
+ struct ocfs2_extent_rec rec;
+
+ BUG_ON(origin != SEEK_DATA && origin != SEEK_HOLE);
+
+ ret = ocfs2_inode_lock(inode, &di_bh, 0);
+ if (ret) {
+ mlog_errno(ret);
+ goto out;
+ }
+
+ down_read(&OCFS2_I(inode)->ip_alloc_sem);
+
+ if (*offset >= inode->i_size) {
+ ret = -ENXIO;
+ goto out_unlock;
+ }
+
+ if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
+ if (origin == SEEK_HOLE)
+ *offset = inode->i_size;
+ goto out_unlock;
+ }
+
+ clen = 0;
+ cpos = *offset >> cs_bits;
+ cend = ocfs2_clusters_for_bytes(inode->i_sb, inode->i_size);
+
+ while (cpos < cend && !is_last) {
+ ret = ocfs2_get_clusters_nocache(inode, di_bh, cpos, &hole_size,
+ &rec, &is_last);
+ if (ret) {
+ mlog_errno(ret);
+ goto out_unlock;
+ }
+
+ extoff = cpos;
+ extoff <<= cs_bits;
+
+ if (rec.e_blkno == 0ULL) {
+ clen = hole_size;
+ is_data = 0;
+ } else {
+ clen = le16_to_cpu(rec.e_leaf_clusters) -
+ (cpos - le32_to_cpu(rec.e_cpos));
+ is_data = (rec.e_flags & OCFS2_EXT_UNWRITTEN) ? 0 : 1;
+ }
+
+ if ((!is_data && origin == SEEK_HOLE) ||
+ (is_data && origin == SEEK_DATA)) {
+ if (extoff > *offset)
+ *offset = extoff;
+ goto out_unlock;
+ }
+
+ if (!is_last)
+ cpos += clen;
+ }
+
+ if (origin == SEEK_HOLE) {
+ extoff = cpos;
+ extoff <<= cs_bits;
+ extlen = clen;
+ extlen <<= cs_bits;
+
+ if ((extoff + extlen) > inode->i_size)
+ extlen = inode->i_size - extoff;
+ extoff += extlen;
+ if (extoff > *offset)
+ *offset = extoff;
+ goto out_unlock;
+ }
+
+ ret = -ENXIO;
+
+out_unlock:
+
+ brelse(di_bh);
+
+ up_read(&OCFS2_I(inode)->ip_alloc_sem);
+
+ ocfs2_inode_unlock(inode, 0);
+out:
+ if (ret && ret != -ENXIO)
+ ret = -ENXIO;
+ 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,