+/**
+ * __jbd2_journal_erase() - Discard or zeroout journal blocks (excluding superblock)
+ * @journal: The journal to erase.
+ * @flags: A discard/zeroout request is sent for each physically contigous
+ * region of the journal. Either JBD2_JOURNAL_FLUSH_DISCARD or
+ * JBD2_JOURNAL_FLUSH_ZEROOUT must be set to determine which operation
+ * to perform.
+ *
+ * Note: JBD2_JOURNAL_FLUSH_ZEROOUT attempts to use hardware offload. Zeroes
+ * will be explicitly written if no hardware offload is available, see
+ * blkdev_issue_zeroout for more details.
+ */
+static int __jbd2_journal_erase(journal_t *journal, unsigned int flags)
+{
+ int err = 0;
+ unsigned long block, log_offset; /* logical */
+ unsigned long long phys_block, block_start, block_stop; /* physical */
+ loff_t byte_start, byte_stop, byte_count;
+ struct request_queue *q = bdev_get_queue(journal->j_dev);
+
+ /* flags must be set to either discard or zeroout */
+ if ((flags & ~JBD2_JOURNAL_FLUSH_VALID) || !flags ||
+ ((flags & JBD2_JOURNAL_FLUSH_DISCARD) &&
+ (flags & JBD2_JOURNAL_FLUSH_ZEROOUT)))
+ return -EINVAL;
+
+ if (!q)
+ return -ENXIO;
+
+ if ((flags & JBD2_JOURNAL_FLUSH_DISCARD) && !blk_queue_discard(q))
+ return -EOPNOTSUPP;
+
+ /*
+ * lookup block mapping and issue discard/zeroout for each
+ * contiguous region
+ */
+ log_offset = be32_to_cpu(journal->j_superblock->s_first);
+ block_start = ~0ULL;
+ for (block = log_offset; block < journal->j_total_len; block++) {
+ err = jbd2_journal_bmap(journal, block, &phys_block);
+ if (err) {
+ pr_err("JBD2: bad block at offset %lu", block);
+ return err;
+ }
+
+ if (block_start == ~0ULL) {
+ block_start = phys_block;
+ block_stop = block_start - 1;
+ }
+
+ /*
+ * last block not contiguous with current block,
+ * process last contiguous region and return to this block on
+ * next loop
+ */
+ if (phys_block != block_stop + 1) {
+ block--;
+ } else {
+ block_stop++;
+ /*
+ * if this isn't the last block of journal,
+ * no need to process now because next block may also
+ * be part of this contiguous region
+ */
+ if (block != journal->j_total_len - 1)
+ continue;
+ }
+
+ /*
+ * end of contiguous region or this is last block of journal,
+ * take care of the region
+ */
+ byte_start = block_start * journal->j_blocksize;
+ byte_stop = block_stop * journal->j_blocksize;
+ byte_count = (block_stop - block_start + 1) *
+ journal->j_blocksize;
+
+ truncate_inode_pages_range(journal->j_dev->bd_inode->i_mapping,
+ byte_start, byte_stop);
+
+ if (flags & JBD2_JOURNAL_FLUSH_DISCARD) {
+ err = blkdev_issue_discard(journal->j_dev,
+ byte_start >> SECTOR_SHIFT,
+ byte_count >> SECTOR_SHIFT,
+ GFP_NOFS, 0);
+ } else if (flags & JBD2_JOURNAL_FLUSH_ZEROOUT) {
+ err = blkdev_issue_zeroout(journal->j_dev,
+ byte_start >> SECTOR_SHIFT,
+ byte_count >> SECTOR_SHIFT,
+ GFP_NOFS, 0);
+ }
+
+ if (unlikely(err != 0)) {
+ pr_err("JBD2: (error %d) unable to wipe journal at physical blocks %llu - %llu",
+ err, block_start, block_stop);
+ return err;
+ }
+
+ /* reset start and stop after processing a region */
+ block_start = ~0ULL;
+ }
+
+ return blkdev_issue_flush(journal->j_dev);
+}