--- /dev/null
+/*
+ * linux/fs/jbd/revoke.c
+ *
+ * Written by Stephen C. Tweedie <sct@redhat.com>, 2000
+ *
+ * Copyright 2000 Red Hat corp --- All Rights Reserved
+ *
+ * This file is part of the Linux kernel and is made available under
+ * the terms of the GNU General Public License, version 2, or at your
+ * option, any later version, incorporated herein by reference.
+ *
+ * Journal revoke routines for the generic filesystem journaling code;
+ * part of the ext2fs journaling system.
+ *
+ * Revoke is the mechanism used to prevent old log records for deleted
+ * metadata from being replayed on top of newer data using the same
+ * blocks. The revoke mechanism is used in two separate places:
+ *
+ * + Commit: during commit we write the entire list of the current
+ * transaction's revoked blocks to the journal
+ *
+ * + Recovery: during recovery we record the transaction ID of all
+ * revoked blocks. If there are multiple revoke records in the log
+ * for a single block, only the last one counts, and if there is a log
+ * entry for a block beyond the last revoke, then that log entry still
+ * gets replayed.
+ *
+ * We can get interactions between revokes and new log data within a
+ * single transaction:
+ *
+ * Block is revoked and then journaled:
+ * The desired end result is the journaling of the new block, so we
+ * cancel the revoke before the transaction commits.
+ *
+ * Block is journaled and then revoked:
+ * The revoke must take precedence over the write of the block, so we
+ * need either to cancel the journal entry or to write the revoke
+ * later in the log than the log block. In this case, we choose the
+ * latter: journaling a block cancels any revoke record for that block
+ * in the current transaction, so any revoke for that block in the
+ * transaction must have happened after the block was journaled and so
+ * the revoke must take precedence.
+ *
+ * Block is revoked and then written as data:
+ * The data write is allowed to succeed, but the revoke is _not_
+ * cancelled. We still need to prevent old log records from
+ * overwriting the new data. We don't even need to clear the revoke
+ * bit here.
+ *
+ * We cache revoke status of a buffer in the current transaction in b_states
+ * bits. As the name says, revokevalid flag indicates that the cached revoke
+ * status of a buffer is valid and we can rely on the cached status.
+ *
+ * Revoke information on buffers is a tri-state value:
+ *
+ * RevokeValid clear: no cached revoke status, need to look it up
+ * RevokeValid set, Revoked clear:
+ * buffer has not been revoked, and cancel_revoke
+ * need do nothing.
+ * RevokeValid set, Revoked set:
+ * buffer has been revoked.
+ *
+ * Locking rules:
+ * We keep two hash tables of revoke records. One hashtable belongs to the
+ * running transaction (is pointed to by journal->j_revoke), the other one
+ * belongs to the committing transaction. Accesses to the second hash table
+ * happen only from the kjournald and no other thread touches this table. Also
+ * journal_switch_revoke_table() which switches which hashtable belongs to the
+ * running and which to the committing transaction is called only from
+ * kjournald. Therefore we need no locks when accessing the hashtable belonging
+ * to the committing transaction.
+ *
+ * All users operating on the hash table belonging to the running transaction
+ * have a handle to the transaction. Therefore they are safe from kjournald
+ * switching hash tables under them. For operations on the lists of entries in
+ * the hash table j_revoke_lock is used.
+ *
+ * Finally, also replay code uses the hash tables but at this moment no one else
+ * can touch them (filesystem isn't mounted yet) and hence no locking is
+ * needed.
+ */
+
+#ifndef __KERNEL__
+#include "jfs_user.h"
+#else
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/jbd.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+#endif
+#include <linux/log2.h>
+#include <linux/hash.h>
+
+static struct kmem_cache *revoke_record_cache;
+static struct kmem_cache *revoke_table_cache;
+
+/* Each revoke record represents one single revoked block. During
+ journal replay, this involves recording the transaction ID of the
+ last transaction to revoke this block. */
+
+struct jbd_revoke_record_s
+{
+ struct list_head hash;
+ tid_t sequence; /* Used for recovery only */
+ unsigned int blocknr;
+};
+
+
+/* The revoke table is just a simple hash table of revoke records. */
+struct jbd_revoke_table_s
+{
+ /* It is conceivable that we might want a larger hash table
+ * for recovery. Must be a power of two. */
+ int hash_size;
+ int hash_shift;
+ struct list_head *hash_table;
+};
+
+
+#ifdef __KERNEL__
+static void write_one_revoke_record(journal_t *, transaction_t *,
+ struct journal_head **, int *,
+ struct jbd_revoke_record_s *, int);
+static void flush_descriptor(journal_t *, struct journal_head *, int, int);
+#endif
+
+/* Utility functions to maintain the revoke table */
+
+static inline int hash(journal_t *journal, unsigned int block)
+{
+ struct jbd_revoke_table_s *table = journal->j_revoke;
+
+ return hash_32(block, table->hash_shift);
+}
+
+static int insert_revoke_hash(journal_t *journal, unsigned int blocknr,
+ tid_t seq)
+{
+ struct list_head *hash_list;
+ struct jbd_revoke_record_s *record;
+
+repeat:
+ record = kmem_cache_alloc(revoke_record_cache, GFP_NOFS);
+ if (!record)
+ goto oom;
+
+ record->sequence = seq;
+ record->blocknr = blocknr;
+ hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
+ spin_lock(&journal->j_revoke_lock);
+ list_add(&record->hash, hash_list);
+ spin_unlock(&journal->j_revoke_lock);
+ return 0;
+
+oom:
+ if (!journal_oom_retry)
+ return -ENOMEM;
+ jbd_debug(1, "ENOMEM in %s, retrying\n", __func__);
+ yield();
+ goto repeat;
+}
+
+/* Find a revoke record in the journal's hash table. */
+
+static struct jbd_revoke_record_s *find_revoke_record(journal_t *journal,
+ unsigned int blocknr)
+{
+ struct list_head *hash_list;
+ struct jbd_revoke_record_s *record;
+
+ hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
+
+ spin_lock(&journal->j_revoke_lock);
+ record = (struct jbd_revoke_record_s *) hash_list->next;
+ while (&(record->hash) != hash_list) {
+ if (record->blocknr == blocknr) {
+ spin_unlock(&journal->j_revoke_lock);
+ return record;
+ }
+ record = (struct jbd_revoke_record_s *) record->hash.next;
+ }
+ spin_unlock(&journal->j_revoke_lock);
+ return NULL;
+}
+
+void journal_destroy_revoke_caches(void)
+{
+ if (revoke_record_cache) {
+ kmem_cache_destroy(revoke_record_cache);
+ revoke_record_cache = NULL;
+ }
+ if (revoke_table_cache) {
+ kmem_cache_destroy(revoke_table_cache);
+ revoke_table_cache = NULL;
+ }
+}
+
+int __init journal_init_revoke_caches(void)
+{
+ J_ASSERT(!revoke_record_cache);
+ J_ASSERT(!revoke_table_cache);
+
+ revoke_record_cache = kmem_cache_create("revoke_record",
+ sizeof(struct jbd_revoke_record_s),
+ 0,
+ SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY,
+ NULL);
+ if (!revoke_record_cache)
+ goto record_cache_failure;
+
+ revoke_table_cache = kmem_cache_create("revoke_table",
+ sizeof(struct jbd_revoke_table_s),
+ 0, SLAB_TEMPORARY, NULL);
+ if (!revoke_table_cache)
+ goto table_cache_failure;
+
+ return 0;
+
+table_cache_failure:
+ journal_destroy_revoke_caches();
+record_cache_failure:
+ return -ENOMEM;
+}
+
+static struct jbd_revoke_table_s *journal_init_revoke_table(int hash_size)
+{
+ int i;
+ struct jbd_revoke_table_s *table;
+
+ table = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
+ if (!table)
+ goto out;
+
+ table->hash_size = hash_size;
+ table->hash_shift = ilog2(hash_size);
+ table->hash_table =
+ kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
+ if (!table->hash_table) {
+ kmem_cache_free(revoke_table_cache, table);
+ table = NULL;
+ goto out;
+ }
+
+ for (i = 0; i < hash_size; i++)
+ INIT_LIST_HEAD(&table->hash_table[i]);
+
+out:
+ return table;
+}
+
+static void journal_destroy_revoke_table(struct jbd_revoke_table_s *table)
+{
+ int i;
+ struct list_head *hash_list;
+
+ for (i = 0; i < table->hash_size; i++) {
+ hash_list = &table->hash_table[i];
+ J_ASSERT(list_empty(hash_list));
+ }
+
+ kfree(table->hash_table);
+ kmem_cache_free(revoke_table_cache, table);
+}
+
+/* Initialise the revoke table for a given journal to a given size. */
+int journal_init_revoke(journal_t *journal, int hash_size)
+{
+ J_ASSERT(journal->j_revoke_table[0] == NULL);
+ J_ASSERT(is_power_of_2(hash_size));
+
+ journal->j_revoke_table[0] = journal_init_revoke_table(hash_size);
+ if (!journal->j_revoke_table[0])
+ goto fail0;
+
+ journal->j_revoke_table[1] = journal_init_revoke_table(hash_size);
+ if (!journal->j_revoke_table[1])
+ goto fail1;
+
+ journal->j_revoke = journal->j_revoke_table[1];
+
+ spin_lock_init(&journal->j_revoke_lock);
+
+ return 0;
+
+fail1:
+ journal_destroy_revoke_table(journal->j_revoke_table[0]);
+fail0:
+ return -ENOMEM;
+}
+
+/* Destroy a journal's revoke table. The table must already be empty! */
+void journal_destroy_revoke(journal_t *journal)
+{
+ journal->j_revoke = NULL;
+ if (journal->j_revoke_table[0])
+ journal_destroy_revoke_table(journal->j_revoke_table[0]);
+ if (journal->j_revoke_table[1])
+ journal_destroy_revoke_table(journal->j_revoke_table[1]);
+}
+
+
+#ifdef __KERNEL__
+
+/*
+ * journal_revoke: revoke a given buffer_head from the journal. This
+ * prevents the block from being replayed during recovery if we take a
+ * crash after this current transaction commits. Any subsequent
+ * metadata writes of the buffer in this transaction cancel the
+ * revoke.
+ *
+ * Note that this call may block --- it is up to the caller to make
+ * sure that there are no further calls to journal_write_metadata
+ * before the revoke is complete. In ext3, this implies calling the
+ * revoke before clearing the block bitmap when we are deleting
+ * metadata.
+ *
+ * Revoke performs a journal_forget on any buffer_head passed in as a
+ * parameter, but does _not_ forget the buffer_head if the bh was only
+ * found implicitly.
+ *
+ * bh_in may not be a journalled buffer - it may have come off
+ * the hash tables without an attached journal_head.
+ *
+ * If bh_in is non-zero, journal_revoke() will decrement its b_count
+ * by one.
+ */
+
+int journal_revoke(handle_t *handle, unsigned int blocknr,
+ struct buffer_head *bh_in)
+{
+ struct buffer_head *bh = NULL;
+ journal_t *journal;
+ struct block_device *bdev;
+ int err;
+
+ might_sleep();
+ if (bh_in)
+ BUFFER_TRACE(bh_in, "enter");
+
+ journal = handle->h_transaction->t_journal;
+ if (!journal_set_features(journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE)){
+ J_ASSERT (!"Cannot set revoke feature!");
+ return -EINVAL;
+ }
+
+ bdev = journal->j_fs_dev;
+ bh = bh_in;
+
+ if (!bh) {
+ bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
+ if (bh)
+ BUFFER_TRACE(bh, "found on hash");
+ }
+#ifdef JBD_EXPENSIVE_CHECKING
+ else {
+ struct buffer_head *bh2;
+
+ /* If there is a different buffer_head lying around in
+ * memory anywhere... */
+ bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
+ if (bh2) {
+ /* ... and it has RevokeValid status... */
+ if (bh2 != bh && buffer_revokevalid(bh2))
+ /* ...then it better be revoked too,
+ * since it's illegal to create a revoke
+ * record against a buffer_head which is
+ * not marked revoked --- that would
+ * risk missing a subsequent revoke
+ * cancel. */
+ J_ASSERT_BH(bh2, buffer_revoked(bh2));
+ put_bh(bh2);
+ }
+ }
+#endif
+
+ /* We really ought not ever to revoke twice in a row without
+ first having the revoke cancelled: it's illegal to free a
+ block twice without allocating it in between! */
+ if (bh) {
+ if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
+ "inconsistent data on disk")) {
+ if (!bh_in)
+ brelse(bh);
+ return -EIO;
+ }
+ set_buffer_revoked(bh);
+ set_buffer_revokevalid(bh);
+ if (bh_in) {
+ BUFFER_TRACE(bh_in, "call journal_forget");
+ journal_forget(handle, bh_in);
+ } else {
+ BUFFER_TRACE(bh, "call brelse");
+ __brelse(bh);
+ }
+ }
+
+ jbd_debug(2, "insert revoke for block %u, bh_in=%p\n", blocknr, bh_in);
+ err = insert_revoke_hash(journal, blocknr,
+ handle->h_transaction->t_tid);
+ BUFFER_TRACE(bh_in, "exit");
+ return err;
+}
+
+/*
+ * Cancel an outstanding revoke. For use only internally by the
+ * journaling code (called from journal_get_write_access).
+ *
+ * We trust buffer_revoked() on the buffer if the buffer is already
+ * being journaled: if there is no revoke pending on the buffer, then we
+ * don't do anything here.
+ *
+ * This would break if it were possible for a buffer to be revoked and
+ * discarded, and then reallocated within the same transaction. In such
+ * a case we would have lost the revoked bit, but when we arrived here
+ * the second time we would still have a pending revoke to cancel. So,
+ * do not trust the Revoked bit on buffers unless RevokeValid is also
+ * set.
+ */
+int journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
+{
+ struct jbd_revoke_record_s *record;
+ journal_t *journal = handle->h_transaction->t_journal;
+ int need_cancel;
+ int did_revoke = 0; /* akpm: debug */
+ struct buffer_head *bh = jh2bh(jh);
+
+ jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
+
+ /* Is the existing Revoke bit valid? If so, we trust it, and
+ * only perform the full cancel if the revoke bit is set. If
+ * not, we can't trust the revoke bit, and we need to do the
+ * full search for a revoke record. */
+ if (test_set_buffer_revokevalid(bh)) {
+ need_cancel = test_clear_buffer_revoked(bh);
+ } else {
+ need_cancel = 1;
+ clear_buffer_revoked(bh);
+ }
+
+ if (need_cancel) {
+ record = find_revoke_record(journal, bh->b_blocknr);
+ if (record) {
+ jbd_debug(4, "cancelled existing revoke on "
+ "blocknr %llu\n", (unsigned long long)bh->b_blocknr);
+ spin_lock(&journal->j_revoke_lock);
+ list_del(&record->hash);
+ spin_unlock(&journal->j_revoke_lock);
+ kmem_cache_free(revoke_record_cache, record);
+ did_revoke = 1;
+ }
+ }
+
+#ifdef JBD_EXPENSIVE_CHECKING
+ /* There better not be one left behind by now! */
+ record = find_revoke_record(journal, bh->b_blocknr);
+ J_ASSERT_JH(jh, record == NULL);
+#endif
+
+ /* Finally, have we just cleared revoke on an unhashed
+ * buffer_head? If so, we'd better make sure we clear the
+ * revoked status on any hashed alias too, otherwise the revoke
+ * state machine will get very upset later on. */
+ if (need_cancel) {
+ struct buffer_head *bh2;
+ bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
+ if (bh2) {
+ if (bh2 != bh)
+ clear_buffer_revoked(bh2);
+ __brelse(bh2);
+ }
+ }
+ return did_revoke;
+}
+
+/*
+ * journal_clear_revoked_flags clears revoked flag of buffers in
+ * revoke table to reflect there is no revoked buffer in the next
+ * transaction which is going to be started.
+ */
+void journal_clear_buffer_revoked_flags(journal_t *journal)
+{
+ struct jbd_revoke_table_s *revoke = journal->j_revoke;
+ int i = 0;
+
+ for (i = 0; i < revoke->hash_size; i++) {
+ struct list_head *hash_list;
+ struct list_head *list_entry;
+ hash_list = &revoke->hash_table[i];
+
+ list_for_each(list_entry, hash_list) {
+ struct jbd_revoke_record_s *record;
+ struct buffer_head *bh;
+ record = (struct jbd_revoke_record_s *)list_entry;
+ bh = __find_get_block(journal->j_fs_dev,
+ record->blocknr,
+ journal->j_blocksize);
+ if (bh) {
+ clear_buffer_revoked(bh);
+ __brelse(bh);
+ }
+ }
+ }
+}
+
+/* journal_switch_revoke table select j_revoke for next transaction
+ * we do not want to suspend any processing until all revokes are
+ * written -bzzz
+ */
+void journal_switch_revoke_table(journal_t *journal)
+{
+ int i;
+
+ if (journal->j_revoke == journal->j_revoke_table[0])
+ journal->j_revoke = journal->j_revoke_table[1];
+ else
+ journal->j_revoke = journal->j_revoke_table[0];
+
+ for (i = 0; i < journal->j_revoke->hash_size; i++)
+ INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
+}
+
+/*
+ * Write revoke records to the journal for all entries in the current
+ * revoke hash, deleting the entries as we go.
+ */
+void journal_write_revoke_records(journal_t *journal,
+ transaction_t *transaction, int write_op)
+{
+ struct journal_head *descriptor;
+ struct jbd_revoke_record_s *record;
+ struct jbd_revoke_table_s *revoke;
+ struct list_head *hash_list;
+ int i, offset, count;
+
+ descriptor = NULL;
+ offset = 0;
+ count = 0;
+
+ /* select revoke table for committing transaction */
+ revoke = journal->j_revoke == journal->j_revoke_table[0] ?
+ journal->j_revoke_table[1] : journal->j_revoke_table[0];
+
+ for (i = 0; i < revoke->hash_size; i++) {
+ hash_list = &revoke->hash_table[i];
+
+ while (!list_empty(hash_list)) {
+ record = (struct jbd_revoke_record_s *)
+ hash_list->next;
+ write_one_revoke_record(journal, transaction,
+ &descriptor, &offset,
+ record, write_op);
+ count++;
+ list_del(&record->hash);
+ kmem_cache_free(revoke_record_cache, record);
+ }
+ }
+ if (descriptor)
+ flush_descriptor(journal, descriptor, offset, write_op);
+ jbd_debug(1, "Wrote %d revoke records\n", count);
+}
+
+/*
+ * Write out one revoke record. We need to create a new descriptor
+ * block if the old one is full or if we have not already created one.
+ */
+
+static void write_one_revoke_record(journal_t *journal,
+ transaction_t *transaction,
+ struct journal_head **descriptorp,
+ int *offsetp,
+ struct jbd_revoke_record_s *record,
+ int write_op)
+{
+ struct journal_head *descriptor;
+ int offset;
+ journal_header_t *header;
+
+ /* If we are already aborting, this all becomes a noop. We
+ still need to go round the loop in
+ journal_write_revoke_records in order to free all of the
+ revoke records: only the IO to the journal is omitted. */
+ if (is_journal_aborted(journal))
+ return;
+
+ descriptor = *descriptorp;
+ offset = *offsetp;
+
+ /* Make sure we have a descriptor with space left for the record */
+ if (descriptor) {
+ if (offset == journal->j_blocksize) {
+ flush_descriptor(journal, descriptor, offset, write_op);
+ descriptor = NULL;
+ }
+ }
+
+ if (!descriptor) {
+ descriptor = journal_get_descriptor_buffer(journal);
+ if (!descriptor)
+ return;
+ header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
+ header->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
+ header->h_blocktype = cpu_to_be32(JFS_REVOKE_BLOCK);
+ header->h_sequence = cpu_to_be32(transaction->t_tid);
+
+ /* Record it so that we can wait for IO completion later */
+ JBUFFER_TRACE(descriptor, "file as BJ_LogCtl");
+ journal_file_buffer(descriptor, transaction, BJ_LogCtl);
+
+ offset = sizeof(journal_revoke_header_t);
+ *descriptorp = descriptor;
+ }
+
+ * ((__be32 *)(&jh2bh(descriptor)->b_data[offset])) =
+ cpu_to_be32(record->blocknr);
+ offset += 4;
+ *offsetp = offset;
+}
+
+/*
+ * Flush a revoke descriptor out to the journal. If we are aborting,
+ * this is a noop; otherwise we are generating a buffer which needs to
+ * be waited for during commit, so it has to go onto the appropriate
+ * journal buffer list.
+ */
+
+static void flush_descriptor(journal_t *journal,
+ struct journal_head *descriptor,
+ int offset, int write_op)
+{
+ journal_revoke_header_t *header;
+ struct buffer_head *bh = jh2bh(descriptor);
+
+ if (is_journal_aborted(journal)) {
+ put_bh(bh);
+ return;
+ }
+
+ header = (journal_revoke_header_t *) jh2bh(descriptor)->b_data;
+ header->r_count = cpu_to_be32(offset);
+ set_buffer_jwrite(bh);
+ BUFFER_TRACE(bh, "write");
+ set_buffer_dirty(bh);
+ write_dirty_buffer(bh, write_op);
+}
+#endif
+
+/*
+ * Revoke support for recovery.
+ *
+ * Recovery needs to be able to:
+ *
+ * record all revoke records, including the tid of the latest instance
+ * of each revoke in the journal
+ *
+ * check whether a given block in a given transaction should be replayed
+ * (ie. has not been revoked by a revoke record in that or a subsequent
+ * transaction)
+ *
+ * empty the revoke table after recovery.
+ */
+
+/*
+ * First, setting revoke records. We create a new revoke record for
+ * every block ever revoked in the log as we scan it for recovery, and
+ * we update the existing records if we find multiple revokes for a
+ * single block.
+ */
+
+int journal_set_revoke(journal_t *journal,
+ unsigned int blocknr,
+ tid_t sequence)
+{
+ struct jbd_revoke_record_s *record;
+
+ record = find_revoke_record(journal, blocknr);
+ if (record) {
+ /* If we have multiple occurrences, only record the
+ * latest sequence number in the hashed record */
+ if (tid_gt(sequence, record->sequence))
+ record->sequence = sequence;
+ return 0;
+ }
+ return insert_revoke_hash(journal, blocknr, sequence);
+}
+
+/*
+ * Test revoke records. For a given block referenced in the log, has
+ * that block been revoked? A revoke record with a given transaction
+ * sequence number revokes all blocks in that transaction and earlier
+ * ones, but later transactions still need replayed.
+ */
+
+int journal_test_revoke(journal_t *journal,
+ unsigned int blocknr,
+ tid_t sequence)
+{
+ struct jbd_revoke_record_s *record;
+
+ record = find_revoke_record(journal, blocknr);
+ if (!record)
+ return 0;
+ if (tid_gt(sequence, record->sequence))
+ return 0;
+ return 1;
+}
+
+/*
+ * Finally, once recovery is over, we need to clear the revoke table so
+ * that it can be reused by the running filesystem.
+ */
+
+void journal_clear_revoke(journal_t *journal)
+{
+ int i;
+ struct list_head *hash_list;
+ struct jbd_revoke_record_s *record;
+ struct jbd_revoke_table_s *revoke;
+
+ revoke = journal->j_revoke;
+
+ for (i = 0; i < revoke->hash_size; i++) {
+ hash_list = &revoke->hash_table[i];
+ while (!list_empty(hash_list)) {
+ record = (struct jbd_revoke_record_s*) hash_list->next;
+ list_del(&record->hash);
+ kmem_cache_free(revoke_record_cache, record);
+ }
+ }
+}
Code Review / kvmfornfv.git / blobdiff