patch-2.4.15 linux/fs/jbd/revoke.c

Next file: linux/fs/jbd/transaction.c
Previous file: linux/fs/jbd/recovery.c
Back to the patch index
Back to the overall index

diff -u --recursive --new-file v2.4.14/linux/fs/jbd/revoke.c linux/fs/jbd/revoke.c
@@ -0,0 +1,631 @@
+/*
+ * linux/fs/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.
+ *
+ * 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.  
+ */
+
+#ifndef __KERNEL__
+#include "jfs_user.h"
+#else
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/jbd.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/locks.h>
+#include <linux/list.h>
+#include <linux/smp_lock.h>
+#include <linux/init.h>
+#endif
+
+static kmem_cache_t *revoke_record_cache;
+static kmem_cache_t *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 long	  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 *);
+static void flush_descriptor(journal_t *, struct journal_head *, int);
+#endif
+
+/* Utility functions to maintain the revoke table */
+
+/* Borrowed from buffer.c: this is a tried and tested block hash function */
+static inline int hash(journal_t *journal, unsigned long block)
+{
+	struct jbd_revoke_table_s *table = journal->j_revoke;
+	int hash_shift = table->hash_shift;
+	
+	return ((block << (hash_shift - 6)) ^
+		(block >> 13) ^
+		(block << (hash_shift - 12))) & (table->hash_size - 1);
+}
+
+int insert_revoke_hash(journal_t *journal, unsigned long 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)];
+	list_add(&record->hash, hash_list);
+	return 0;
+
+oom:
+	if (!journal_oom_retry)
+		return -ENOMEM;
+	jbd_debug(1, "ENOMEM in " __FUNCTION__ ", retrying.\n");
+	current->policy |= SCHED_YIELD;
+	schedule();
+	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 long blocknr)
+{
+	struct list_head *hash_list;
+	struct jbd_revoke_record_s *record;
+	
+	hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
+
+	record = (struct jbd_revoke_record_s *) hash_list->next;
+	while (&(record->hash) != hash_list) {
+		if (record->blocknr == blocknr)
+			return record;
+		record = (struct jbd_revoke_record_s *) record->hash.next;
+	}
+	return NULL;
+}
+
+int __init journal_init_revoke_caches(void)
+{
+	revoke_record_cache = kmem_cache_create("revoke_record",
+					   sizeof(struct jbd_revoke_record_s),
+					   0, SLAB_HWCACHE_ALIGN, NULL, NULL);
+	if (revoke_record_cache == 0)
+		return -ENOMEM;
+
+	revoke_table_cache = kmem_cache_create("revoke_table",
+					   sizeof(struct jbd_revoke_table_s),
+					   0, 0, NULL, NULL);
+	if (revoke_table_cache == 0) {
+		kmem_cache_destroy(revoke_record_cache);
+		revoke_record_cache = NULL;
+		return -ENOMEM;
+	}
+	return 0;
+}	
+
+void journal_destroy_revoke_caches(void)
+{
+	kmem_cache_destroy(revoke_record_cache);
+	revoke_record_cache = 0;
+	kmem_cache_destroy(revoke_table_cache);
+	revoke_table_cache = 0;
+}
+
+/* Initialise the revoke table for a given journal to a given size. */
+
+int journal_init_revoke(journal_t *journal, int hash_size)
+{
+	int shift, tmp;
+	
+	J_ASSERT (journal->j_revoke == NULL);
+	
+	journal->j_revoke = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
+	if (!journal->j_revoke)
+		return -ENOMEM;
+	
+	/* Check that the hash_size is a power of two */
+	J_ASSERT ((hash_size & (hash_size-1)) == 0);
+
+	journal->j_revoke->hash_size = hash_size;
+
+	shift = 0;
+	tmp = hash_size;
+	while((tmp >>= 1UL) != 0UL)
+		shift++;
+	journal->j_revoke->hash_shift = shift;
+
+	journal->j_revoke->hash_table =
+		kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
+	if (!journal->j_revoke->hash_table) {
+		kmem_cache_free(revoke_table_cache, journal->j_revoke);
+		journal->j_revoke = NULL;
+		return -ENOMEM;
+	}
+	
+	for (tmp = 0; tmp < hash_size; tmp++)
+		INIT_LIST_HEAD(&journal->j_revoke->hash_table[tmp]);
+	
+	return 0;
+}
+
+/* Destoy a journal's revoke table.  The table must already be empty! */
+
+void journal_destroy_revoke(journal_t *journal)
+{
+	struct jbd_revoke_table_s *table;
+	struct list_head *hash_list;
+	int i;
+	
+	table = journal->j_revoke;
+	if (!table)
+		return;
+	
+	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);
+	journal->j_revoke = NULL;
+}
+
+
+#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 long blocknr, 
+		   struct buffer_head *bh_in)
+{
+	struct buffer_head *bh = NULL;
+	journal_t *journal;
+	kdev_t dev;
+	int err;
+
+	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;
+	}
+
+	dev = journal->j_fs_dev;
+	bh = bh_in;
+
+	if (!bh) {
+		bh = get_hash_table(dev, 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 = get_hash_table(dev, blocknr, journal->j_blocksize);
+		if (bh2) {
+			/* ... and it has RevokeValid status... */
+			if ((bh2 != bh) &&
+			    test_bit(BH_RevokeValid, &bh2->b_state))
+				/* ...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, test_bit(BH_Revoked, &
+							  bh2->b_state));
+			__brelse(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) {
+		J_ASSERT_BH(bh, !test_bit(BH_Revoked, &bh->b_state));
+		set_bit(BH_Revoked, &bh->b_state);
+		set_bit(BH_RevokeValid, &bh->b_state);
+		if (bh_in) {
+			BUFFER_TRACE(bh_in, "call journal_forget");
+			journal_forget(handle, bh_in);
+		} else {
+			BUFFER_TRACE(bh, "call brelse");
+			__brelse(bh);
+		}
+	}
+
+	lock_journal(journal);
+	jbd_debug(2, "insert revoke for block %lu, bh_in=%p\n", blocknr, bh_in);
+	err = insert_revoke_hash(journal, blocknr,
+				handle->h_transaction->t_tid);
+	unlock_journal(journal);
+	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 the BH_Revoked bit 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.
+ *
+ * The caller must have the journal locked.
+ */
+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_and_set_bit(BH_RevokeValid, &bh->b_state))
+		need_cancel = (test_and_clear_bit(BH_Revoked, &bh->b_state));
+	else {
+		need_cancel = 1;
+		clear_bit(BH_Revoked, &bh->b_state);
+	}
+
+	if (need_cancel) {
+		record = find_revoke_record(journal, bh->b_blocknr);
+		if (record) {
+			jbd_debug(4, "cancelled existing revoke on "
+				  "blocknr %lu\n", bh->b_blocknr);
+			list_del(&record->hash);
+			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 && !bh->b_pprev) {
+		struct buffer_head *bh2;
+		bh2 = get_hash_table(bh->b_dev, bh->b_blocknr, bh->b_size);
+		if (bh2) {
+			clear_bit(BH_Revoked, &bh2->b_state);
+			__brelse(bh2);
+		}
+	}
+	
+	return did_revoke;
+}
+
+
+/*
+ * Write revoke records to the journal for all entries in the current
+ * revoke hash, deleting the entries as we go.
+ *
+ * Called with the journal lock held.
+ */
+
+void journal_write_revoke_records(journal_t *journal, 
+				  transaction_t *transaction)
+{
+	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;
+	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;
+			write_one_revoke_record(journal, transaction,
+						&descriptor, &offset, 
+						record);
+			count++;
+			list_del(&record->hash);
+			kmem_cache_free(revoke_record_cache, record);
+		}
+	}
+	if (descriptor) 
+		flush_descriptor(journal, descriptor, offset);
+	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)
+{
+	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);
+			descriptor = NULL;
+		}
+	}
+	
+	if (!descriptor) {
+		descriptor = journal_get_descriptor_buffer(journal);
+		header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
+		header->h_magic     = htonl(JFS_MAGIC_NUMBER);
+		header->h_blocktype = htonl(JFS_REVOKE_BLOCK);
+		header->h_sequence  = htonl(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;
+	}
+	
+	* ((unsigned int *)(&jh2bh(descriptor)->b_data[offset])) = 
+		htonl(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)
+{
+	journal_revoke_header_t *header;
+
+	if (is_journal_aborted(journal)) {
+		JBUFFER_TRACE(descriptor, "brelse");
+		__brelse(jh2bh(descriptor));
+		return;
+	}
+	
+	header = (journal_revoke_header_t *) jh2bh(descriptor)->b_data;
+	header->r_count = htonl(offset);
+	set_bit(BH_JWrite, &jh2bh(descriptor)->b_state);
+	{
+		struct buffer_head *bh = jh2bh(descriptor);
+		BUFFER_TRACE(bh, "write");
+		ll_rw_block (WRITE, 1, &bh);
+	}
+}
+
+#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 long blocknr, 
+		       tid_t sequence)
+{
+	struct jbd_revoke_record_s *record;
+	
+	record = find_revoke_record(journal, blocknr);
+	if (record) {
+		/* If we have multiple occurences, 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 long 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);
+		}
+	}
+}
+
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)