ref: 3cf7bf8bd1bc13387a957f8032f68ed0202ac6e9
parent: b465297573ef0ae41d3a2cdbcb5528f3388ba6d9
author: ngkaho1234 <ngkaho1234@gmail.com>
date: Thu Dec 17 18:17:02 EST 2015
ext4_journal: add comments to the code part 2.
--- a/lwext4/ext4_journal.c
+++ b/lwext4/ext4_journal.c
@@ -587,6 +587,9 @@
return RB_FIND(jbd_revoke, &info->revoke_root, &tmp);
}
+/**@brief Replay a block in a transaction.
+ * @param jbd_fs jbd filesystem
+ * @param block block address to be replayed.*/
static void jbd_replay_block_tags(struct jbd_fs *jbd_fs,
ext4_fsblk_t block,
uint8_t *uuid __unused,
@@ -602,6 +605,8 @@
(*this_block)++;
+ /* We replay this block only if the current transaction id
+ * is equal or greater than that in revoke entry.*/
revoke_entry = jbd_revoke_entry_lookup(info, block);
if (revoke_entry &&
arg->this_trans_id < revoke_entry->trans_id)
@@ -615,6 +620,7 @@
if (r != EOK)
return;
+ /* We need special treatment for ext4 superblock. */
if (block) {r = ext4_block_get_noread(fs->bdev, &ext4_block, block);
if (r != EOK) {@@ -652,6 +658,10 @@
return;
}
+/**@brief Add block address to revoke tree, along with
+ * its transaction id.
+ * @param info journal replay info
+ * @param block block address to be replayed.*/
static void jbd_add_revoke_block_tags(struct recover_info *info,
ext4_fsblk_t block)
{@@ -658,6 +668,8 @@
struct revoke_entry *revoke_entry;
ext4_dbg(DEBUG_JBD, "Add block %" PRIu64 " to revoke tree\n", block);
+ /* If the revoke entry with respect to the block address
+ * exists already, update its transaction id.*/
revoke_entry = jbd_revoke_entry_lookup(info, block);
if (revoke_entry) {revoke_entry->trans_id = info->this_trans_id;
@@ -695,7 +707,10 @@
#define ACTION_REVOKE 1
#define ACTION_RECOVER 2
-
+/**@brief Add entries in a revoke block to revoke tree.
+ * @param jbd_fs jbd filesystem
+ * @param header revoke block header
+ * @param recover_info journal replay info*/
static void jbd_build_revoke_tree(struct jbd_fs *jbd_fs,
struct jbd_bhdr *header,
struct recover_info *info)
@@ -704,6 +719,8 @@
struct jbd_revoke_header *revoke_hdr =
(struct jbd_revoke_header *)header;
uint32_t i, nr_entries, record_len = 4;
+
+ /* If we are working on a 64bit jbd filesystem, */
if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb,
JBD_FEATURE_INCOMPAT_64BIT))
record_len = 8;
@@ -752,6 +769,11 @@
arg);
}
+/**@brief The core routine of journal replay.
+ * @param jbd_fs jbd filesystem
+ * @param recover_info journal replay info
+ * @param action action needed to be taken
+ * @return standard error code*/
int jbd_iterate_log(struct jbd_fs *jbd_fs,
struct recover_info *info,
int action)
@@ -762,6 +784,7 @@
uint32_t start_trans_id, this_trans_id;
uint32_t start_block, this_block;
+ /* We start iterating valid blocks in the whole journal.*/
start_trans_id = this_trans_id = jbd_get32(sb, sequence);
start_block = this_block = jbd_get32(sb, start);
@@ -771,6 +794,10 @@
while (!log_end) {struct ext4_block block;
struct jbd_bhdr *header;
+ /* If we are not scanning for the last
+ * valid transaction in the journal,
+ * we will stop when we reach the end of
+ * the journal.*/
if (action != ACTION_SCAN)
if (this_trans_id > info->last_trans_id) {log_end = true;
@@ -782,6 +809,8 @@
break;
header = (struct jbd_bhdr *)block.data;
+ /* This block does not have a valid magic number,
+ * so we have reached the end of the journal.*/
if (jbd_get32(header, magic) != JBD_MAGIC_NUMBER) {jbd_block_set(jbd_fs, &block);
log_end = true;
@@ -788,6 +817,11 @@
continue;
}
+ /* If the transaction id we found is not expected,
+ * we may have reached the end of the journal.
+ *
+ * If we are not scanning the journal, something
+ * bad might have taken place. :-( */
if (jbd_get32(header, sequence) != this_trans_id) {if (action != ACTION_SCAN)
r = EIO;
@@ -819,6 +853,9 @@
ext4_dbg(DEBUG_JBD, "Commit block: %" PRIu32", "
"trans_id: %" PRIu32"\n",
this_block, this_trans_id);
+ /* This is the end of a transaction,
+ * we may now proceed to the next transaction.
+ */
this_trans_id++;
break;
case JBD_REVOKE_BLOCK:
@@ -844,6 +881,7 @@
}
ext4_dbg(DEBUG_JBD, "End of journal.\n");
if (r == EOK && action == ACTION_SCAN) {+ /* We have finished scanning the journal. */
info->start_trans_id = start_trans_id;
if (this_trans_id > start_trans_id)
info->last_trans_id = this_trans_id - 1;
@@ -854,6 +892,9 @@
return r;
}
+/**@brief Replay journal.
+ * @param jbd_fs jbd filesystem
+ * @return standard error code*/
int jbd_recover(struct jbd_fs *jbd_fs)
{int r;
@@ -874,6 +915,10 @@
r = jbd_iterate_log(jbd_fs, &info, ACTION_RECOVER);
if (r == EOK) {+ /* If we successfully replay the journal,
+ * clear EXT4_FINCOM_RECOVER flag on the
+ * ext4 superblock, and set the start of
+ * journal to 0.*/
uint32_t features_incompatible =
ext4_get32(&jbd_fs->inode_ref.fs->sb,
features_incompatible);
@@ -898,6 +943,10 @@
jbd_fs->dirty = true;
}
+/**@brief Start accessing the journal.
+ * @param jbd_fs jbd filesystem
+ * @param journal current journal session
+ * @return standard error code*/
int jbd_journal_start(struct jbd_fs *jbd_fs,
struct jbd_journal *journal)
{@@ -929,14 +978,19 @@
return jbd_write_sb(jbd_fs);
}
+/**@brief Stop accessing the journal.
+ * @param journal current journal session
+ * @return standard error code*/
int jbd_journal_stop(struct jbd_journal *journal)
{-
int r;
struct jbd_fs *jbd_fs = journal->jbd_fs;
uint32_t features_incompatible;
+ /* Commit all the transactions to the journal.*/
jbd_journal_commit_all(journal);
+ /* Make sure that journalled content have reached
+ * the disk.*/
ext4_block_cache_flush(jbd_fs->inode_ref.fs->bdev);
features_incompatible =
@@ -957,6 +1011,10 @@
return jbd_write_sb(journal->jbd_fs);
}
+/**@brief Allocate a block in the journal.
+ * @param journal current journal session
+ * @param trans transaction
+ * @return allocated block address*/
static uint32_t jbd_journal_alloc_block(struct jbd_journal *journal,
struct jbd_trans *trans)
{@@ -965,6 +1023,9 @@
start_block = journal->last++;
trans->alloc_blocks++;
wrap(&journal->jbd_fs->sb, journal->last);
+
+ /* If there is no space left, flush all journalled
+ * blocks to disk first.*/
if (journal->last == journal->start)
ext4_block_cache_flush(journal->jbd_fs->inode_ref.fs->bdev);
@@ -971,6 +1032,9 @@
return start_block;
}
+/**@brief Allocate a new transaction
+ * @param journal current journal session
+ * @return transaction allocated*/
struct jbd_trans *
jbd_journal_new_trans(struct jbd_journal *journal)
{@@ -990,6 +1054,10 @@
int res,
void *arg);
+/**@brief Add block to a transaction
+ * @param trans transaction
+ * @param block block descriptor
+ * @return standard error code*/
int jbd_trans_add_block(struct jbd_trans *trans,
struct ext4_block *block)
{@@ -1007,6 +1075,8 @@
buf->block = *block;
ext4_bcache_inc_ref(block->buf);
+ /* If the content reach the disk, notify us
+ * so that we may do a checkpoint. */
block->buf->end_write = jbd_trans_end_write;
block->buf->end_write_arg = trans;
@@ -1015,6 +1085,10 @@
return EOK;
}
+/**@brief Add block to be revoked to a transaction
+ * @param trans transaction
+ * @param lba logical block address
+ * @return standard error code*/
int jbd_trans_revoke_block(struct jbd_trans *trans,
ext4_fsblk_t lba)
{@@ -1028,6 +1102,11 @@
return EOK;
}
+/**@brief Free a transaction
+ * @param journal current journal session
+ * @param trans transaction
+ * @param abort discard all the modifications on the block?
+ * @return standard error code*/
void jbd_journal_free_trans(struct jbd_journal *journal,
struct jbd_trans *trans,
bool abort)
@@ -1052,6 +1131,9 @@
free(trans);
}
+/**@brief Write commit block for a transaction
+ * @param trans transaction
+ * @return standard error code*/
static int jbd_trans_write_commit_block(struct jbd_trans *trans)
{int rc;
@@ -1079,6 +1161,10 @@
return EOK;
}
+/**@brief Write descriptor block for a transaction
+ * @param journal current journal session
+ * @param trans transaction
+ * @return standard error code*/
static int jbd_journal_prepare(struct jbd_journal *journal,
struct jbd_trans *trans)
{@@ -1164,6 +1250,10 @@
return rc;
}
+/**@brief Write revoke block for a transaction
+ * @param journal current journal session
+ * @param trans transaction
+ * @return standard error code*/
static int
jbd_journal_prepare_revoke(struct jbd_journal *journal,
struct jbd_trans *trans)
@@ -1243,6 +1333,9 @@
return rc;
}
+/**@brief Submit the transaction to transaction queue.
+ * @param journal current journal session
+ * @param trans transaction*/
void
jbd_journal_submit_trans(struct jbd_journal *journal,
struct jbd_trans *trans)
@@ -1252,6 +1345,9 @@
trans_node);
}
+/**@brief Put references of block descriptors in a transaction.
+ * @param journal current journal session
+ * @param trans transaction*/
void jbd_journal_cp_trans(struct jbd_journal *journal, struct jbd_trans *trans)
{struct jbd_buf *jbd_buf, *tmp;
@@ -1263,6 +1359,8 @@
}
}
+/**@brief Update the start block of the journal when
+ * all the contents in a transaction reach the disk.*/
static void jbd_trans_end_write(struct ext4_bcache *bc __unused,
struct ext4_buf *buf __unused,
int res,
@@ -1312,6 +1410,9 @@
}
}
+/**@brief Commit one transaction on transaction queue
+ * to the journal.
+ * @param journal current journal session.*/
void jbd_journal_commit_one(struct jbd_journal *journal)
{int rc = EOK;
@@ -1368,6 +1469,9 @@
}
}
+/**@brief Commit all the transactions on transaction queue
+ * to the journal.
+ * @param journal current journal session.*/
void jbd_journal_commit_all(struct jbd_journal *journal)
{ while (!TAILQ_EMPTY(&journal->trans_queue)) {