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linux-sg2042/fs/jbd/journal.c

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/*
* linux/fs/jbd/journal.c
*
* Written by Stephen C. Tweedie <sct@redhat.com>, 1998
*
* Copyright 1998 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.
*
* Generic filesystem journal-writing code; part of the ext2fs
* journaling system.
*
* This file manages journals: areas of disk reserved for logging
* transactional updates. This includes the kernel journaling thread
* which is responsible for scheduling updates to the log.
*
* We do not actually manage the physical storage of the journal in this
* file: that is left to a per-journal policy function, which allows us
* to store the journal within a filesystem-specified area for ext2
* journaling (ext2 can use a reserved inode for storing the log).
*/
#include <linux/module.h>
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/freezer.h>
#include <linux/pagemap.h>
#include <linux/kthread.h>
#include <linux/poison.h>
#include <linux/proc_fs.h>
#include <linux/debugfs.h>
#include <asm/uaccess.h>
#include <asm/page.h>
EXPORT_SYMBOL(journal_start);
EXPORT_SYMBOL(journal_restart);
EXPORT_SYMBOL(journal_extend);
EXPORT_SYMBOL(journal_stop);
EXPORT_SYMBOL(journal_lock_updates);
EXPORT_SYMBOL(journal_unlock_updates);
EXPORT_SYMBOL(journal_get_write_access);
EXPORT_SYMBOL(journal_get_create_access);
EXPORT_SYMBOL(journal_get_undo_access);
EXPORT_SYMBOL(journal_dirty_data);
EXPORT_SYMBOL(journal_dirty_metadata);
EXPORT_SYMBOL(journal_release_buffer);
EXPORT_SYMBOL(journal_forget);
#if 0
EXPORT_SYMBOL(journal_sync_buffer);
#endif
EXPORT_SYMBOL(journal_flush);
EXPORT_SYMBOL(journal_revoke);
EXPORT_SYMBOL(journal_init_dev);
EXPORT_SYMBOL(journal_init_inode);
EXPORT_SYMBOL(journal_update_format);
EXPORT_SYMBOL(journal_check_used_features);
EXPORT_SYMBOL(journal_check_available_features);
EXPORT_SYMBOL(journal_set_features);
EXPORT_SYMBOL(journal_create);
EXPORT_SYMBOL(journal_load);
EXPORT_SYMBOL(journal_destroy);
EXPORT_SYMBOL(journal_abort);
EXPORT_SYMBOL(journal_errno);
EXPORT_SYMBOL(journal_ack_err);
EXPORT_SYMBOL(journal_clear_err);
EXPORT_SYMBOL(log_wait_commit);
EXPORT_SYMBOL(journal_start_commit);
EXPORT_SYMBOL(journal_force_commit_nested);
EXPORT_SYMBOL(journal_wipe);
EXPORT_SYMBOL(journal_blocks_per_page);
EXPORT_SYMBOL(journal_invalidatepage);
EXPORT_SYMBOL(journal_try_to_free_buffers);
EXPORT_SYMBOL(journal_force_commit);
static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
static void __journal_abort_soft (journal_t *journal, int errno);
/*
* Helper function used to manage commit timeouts
*/
static void commit_timeout(unsigned long __data)
{
struct task_struct * p = (struct task_struct *) __data;
wake_up_process(p);
}
/*
* kjournald: The main thread function used to manage a logging device
* journal.
*
* This kernel thread is responsible for two things:
*
* 1) COMMIT: Every so often we need to commit the current state of the
* filesystem to disk. The journal thread is responsible for writing
* all of the metadata buffers to disk.
*
* 2) CHECKPOINT: We cannot reuse a used section of the log file until all
* of the data in that part of the log has been rewritten elsewhere on
* the disk. Flushing these old buffers to reclaim space in the log is
* known as checkpointing, and this thread is responsible for that job.
*/
static int kjournald(void *arg)
{
journal_t *journal = arg;
transaction_t *transaction;
/*
* Set up an interval timer which can be used to trigger a commit wakeup
* after the commit interval expires
*/
setup_timer(&journal->j_commit_timer, commit_timeout,
(unsigned long)current);
/* Record that the journal thread is running */
journal->j_task = current;
wake_up(&journal->j_wait_done_commit);
printk(KERN_INFO "kjournald starting. Commit interval %ld seconds\n",
journal->j_commit_interval / HZ);
/*
* And now, wait forever for commit wakeup events.
*/
spin_lock(&journal->j_state_lock);
loop:
if (journal->j_flags & JFS_UNMOUNT)
goto end_loop;
jbd_debug(1, "commit_sequence=%d, commit_request=%d\n",
journal->j_commit_sequence, journal->j_commit_request);
if (journal->j_commit_sequence != journal->j_commit_request) {
jbd_debug(1, "OK, requests differ\n");
spin_unlock(&journal->j_state_lock);
del_timer_sync(&journal->j_commit_timer);
journal_commit_transaction(journal);
spin_lock(&journal->j_state_lock);
goto loop;
}
wake_up(&journal->j_wait_done_commit);
if (freezing(current)) {
/*
* The simpler the better. Flushing journal isn't a
* good idea, because that depends on threads that may
* be already stopped.
*/
jbd_debug(1, "Now suspending kjournald\n");
spin_unlock(&journal->j_state_lock);
refrigerator();
spin_lock(&journal->j_state_lock);
} else {
/*
* We assume on resume that commits are already there,
* so we don't sleep
*/
DEFINE_WAIT(wait);
int should_sleep = 1;
prepare_to_wait(&journal->j_wait_commit, &wait,
TASK_INTERRUPTIBLE);
if (journal->j_commit_sequence != journal->j_commit_request)
should_sleep = 0;
transaction = journal->j_running_transaction;
if (transaction && time_after_eq(jiffies,
transaction->t_expires))
should_sleep = 0;
if (journal->j_flags & JFS_UNMOUNT)
should_sleep = 0;
if (should_sleep) {
spin_unlock(&journal->j_state_lock);
schedule();
spin_lock(&journal->j_state_lock);
}
finish_wait(&journal->j_wait_commit, &wait);
}
jbd_debug(1, "kjournald wakes\n");
/*
* Were we woken up by a commit wakeup event?
*/
transaction = journal->j_running_transaction;
if (transaction && time_after_eq(jiffies, transaction->t_expires)) {
journal->j_commit_request = transaction->t_tid;
jbd_debug(1, "woke because of timeout\n");
}
goto loop;
end_loop:
spin_unlock(&journal->j_state_lock);
del_timer_sync(&journal->j_commit_timer);
journal->j_task = NULL;
wake_up(&journal->j_wait_done_commit);
jbd_debug(1, "Journal thread exiting.\n");
return 0;
}
static int journal_start_thread(journal_t *journal)
{
struct task_struct *t;
t = kthread_run(kjournald, journal, "kjournald");
if (IS_ERR(t))
return PTR_ERR(t);
wait_event(journal->j_wait_done_commit, journal->j_task != NULL);
return 0;
}
static void journal_kill_thread(journal_t *journal)
{
spin_lock(&journal->j_state_lock);
journal->j_flags |= JFS_UNMOUNT;
while (journal->j_task) {
wake_up(&journal->j_wait_commit);
spin_unlock(&journal->j_state_lock);
wait_event(journal->j_wait_done_commit,
journal->j_task == NULL);
spin_lock(&journal->j_state_lock);
}
spin_unlock(&journal->j_state_lock);
}
/*
* journal_write_metadata_buffer: write a metadata buffer to the journal.
*
* Writes a metadata buffer to a given disk block. The actual IO is not
* performed but a new buffer_head is constructed which labels the data
* to be written with the correct destination disk block.
*
* Any magic-number escaping which needs to be done will cause a
* copy-out here. If the buffer happens to start with the
* JFS_MAGIC_NUMBER, then we can't write it to the log directly: the
* magic number is only written to the log for descripter blocks. In
* this case, we copy the data and replace the first word with 0, and we
* return a result code which indicates that this buffer needs to be
* marked as an escaped buffer in the corresponding log descriptor
* block. The missing word can then be restored when the block is read
* during recovery.
*
* If the source buffer has already been modified by a new transaction
* since we took the last commit snapshot, we use the frozen copy of
* that data for IO. If we end up using the existing buffer_head's data
* for the write, then we *have* to lock the buffer to prevent anyone
* else from using and possibly modifying it while the IO is in
* progress.
*
* The function returns a pointer to the buffer_heads to be used for IO.
*
* We assume that the journal has already been locked in this function.
*
* Return value:
* <0: Error
* >=0: Finished OK
*
* On success:
* Bit 0 set == escape performed on the data
* Bit 1 set == buffer copy-out performed (kfree the data after IO)
*/
int journal_write_metadata_buffer(transaction_t *transaction,
struct journal_head *jh_in,
struct journal_head **jh_out,
unsigned long blocknr)
{
int need_copy_out = 0;
int done_copy_out = 0;
int do_escape = 0;
char *mapped_data;
struct buffer_head *new_bh;
struct journal_head *new_jh;
struct page *new_page;
unsigned int new_offset;
struct buffer_head *bh_in = jh2bh(jh_in);
/*
* The buffer really shouldn't be locked: only the current committing
* transaction is allowed to write it, so nobody else is allowed
* to do any IO.
*
* akpm: except if we're journalling data, and write() output is
* also part of a shared mapping, and another thread has
* decided to launch a writepage() against this buffer.
*/
J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));
new_bh = alloc_buffer_head(GFP_NOFS|__GFP_NOFAIL);
/*
* If a new transaction has already done a buffer copy-out, then
* we use that version of the data for the commit.
*/
jbd_lock_bh_state(bh_in);
repeat:
if (jh_in->b_frozen_data) {
done_copy_out = 1;
new_page = virt_to_page(jh_in->b_frozen_data);
new_offset = offset_in_page(jh_in->b_frozen_data);
} else {
new_page = jh2bh(jh_in)->b_page;
new_offset = offset_in_page(jh2bh(jh_in)->b_data);
}
mapped_data = kmap_atomic(new_page, KM_USER0);
/*
* Check for escaping
*/
if (*((__be32 *)(mapped_data + new_offset)) ==
cpu_to_be32(JFS_MAGIC_NUMBER)) {
need_copy_out = 1;
do_escape = 1;
}
kunmap_atomic(mapped_data, KM_USER0);
/*
* Do we need to do a data copy?
*/
if (need_copy_out && !done_copy_out) {
char *tmp;
jbd_unlock_bh_state(bh_in);
tmp = jbd_alloc(bh_in->b_size, GFP_NOFS);
jbd_lock_bh_state(bh_in);
if (jh_in->b_frozen_data) {
jbd_free(tmp, bh_in->b_size);
goto repeat;
}
jh_in->b_frozen_data = tmp;
mapped_data = kmap_atomic(new_page, KM_USER0);
memcpy(tmp, mapped_data + new_offset, jh2bh(jh_in)->b_size);
kunmap_atomic(mapped_data, KM_USER0);
new_page = virt_to_page(tmp);
new_offset = offset_in_page(tmp);
done_copy_out = 1;
}
/*
* Did we need to do an escaping? Now we've done all the
* copying, we can finally do so.
*/
if (do_escape) {
mapped_data = kmap_atomic(new_page, KM_USER0);
*((unsigned int *)(mapped_data + new_offset)) = 0;
kunmap_atomic(mapped_data, KM_USER0);
}
/* keep subsequent assertions sane */
new_bh->b_state = 0;
init_buffer(new_bh, NULL, NULL);
atomic_set(&new_bh->b_count, 1);
jbd_unlock_bh_state(bh_in);
new_jh = journal_add_journal_head(new_bh); /* This sleeps */
set_bh_page(new_bh, new_page, new_offset);
new_jh->b_transaction = NULL;
new_bh->b_size = jh2bh(jh_in)->b_size;
new_bh->b_bdev = transaction->t_journal->j_dev;
new_bh->b_blocknr = blocknr;
set_buffer_mapped(new_bh);
set_buffer_dirty(new_bh);
*jh_out = new_jh;
/*
* The to-be-written buffer needs to get moved to the io queue,
* and the original buffer whose contents we are shadowing or
* copying is moved to the transaction's shadow queue.
*/
JBUFFER_TRACE(jh_in, "file as BJ_Shadow");
journal_file_buffer(jh_in, transaction, BJ_Shadow);
JBUFFER_TRACE(new_jh, "file as BJ_IO");
journal_file_buffer(new_jh, transaction, BJ_IO);
return do_escape | (done_copy_out << 1);
}
/*
* Allocation code for the journal file. Manage the space left in the
* journal, so that we can begin checkpointing when appropriate.
*/
/*
* __log_space_left: Return the number of free blocks left in the journal.
*
* Called with the journal already locked.
*
* Called under j_state_lock
*/
int __log_space_left(journal_t *journal)
{
int left = journal->j_free;
assert_spin_locked(&journal->j_state_lock);
/*
* Be pessimistic here about the number of those free blocks which
* might be required for log descriptor control blocks.
*/
#define MIN_LOG_RESERVED_BLOCKS 32 /* Allow for rounding errors */
left -= MIN_LOG_RESERVED_BLOCKS;
if (left <= 0)
return 0;
left -= (left >> 3);
return left;
}
/*
* Called under j_state_lock. Returns true if a transaction was started.
*/
int __log_start_commit(journal_t *journal, tid_t target)
{
/*
* Are we already doing a recent enough commit?
*/
if (!tid_geq(journal->j_commit_request, target)) {
/*
* We want a new commit: OK, mark the request and wakup the
* commit thread. We do _not_ do the commit ourselves.
*/
journal->j_commit_request = target;
jbd_debug(1, "JBD: requesting commit %d/%d\n",
journal->j_commit_request,
journal->j_commit_sequence);
wake_up(&journal->j_wait_commit);
return 1;
}
return 0;
}
int log_start_commit(journal_t *journal, tid_t tid)
{
int ret;
spin_lock(&journal->j_state_lock);
ret = __log_start_commit(journal, tid);
spin_unlock(&journal->j_state_lock);
return ret;
}
/*
* Force and wait upon a commit if the calling process is not within
* transaction. This is used for forcing out undo-protected data which contains
* bitmaps, when the fs is running out of space.
*
* We can only force the running transaction if we don't have an active handle;
* otherwise, we will deadlock.
*
* Returns true if a transaction was started.
*/
int journal_force_commit_nested(journal_t *journal)
{
transaction_t *transaction = NULL;
tid_t tid;
spin_lock(&journal->j_state_lock);
if (journal->j_running_transaction && !current->journal_info) {
transaction = journal->j_running_transaction;
__log_start_commit(journal, transaction->t_tid);
} else if (journal->j_committing_transaction)
transaction = journal->j_committing_transaction;
if (!transaction) {
spin_unlock(&journal->j_state_lock);
return 0; /* Nothing to retry */
}
tid = transaction->t_tid;
spin_unlock(&journal->j_state_lock);
log_wait_commit(journal, tid);
return 1;
}
/*
* Start a commit of the current running transaction (if any). Returns true
* if a transaction was started, and fills its tid in at *ptid
*/
int journal_start_commit(journal_t *journal, tid_t *ptid)
{
int ret = 0;
spin_lock(&journal->j_state_lock);
if (journal->j_running_transaction) {
tid_t tid = journal->j_running_transaction->t_tid;
ret = __log_start_commit(journal, tid);
if (ret && ptid)
*ptid = tid;
} else if (journal->j_committing_transaction && ptid) {
/*
* If ext3_write_super() recently started a commit, then we
* have to wait for completion of that transaction
*/
*ptid = journal->j_committing_transaction->t_tid;
ret = 1;
}
spin_unlock(&journal->j_state_lock);
return ret;
}
/*
* Wait for a specified commit to complete.
* The caller may not hold the journal lock.
*/
int log_wait_commit(journal_t *journal, tid_t tid)
{
int err = 0;
#ifdef CONFIG_JBD_DEBUG
spin_lock(&journal->j_state_lock);
if (!tid_geq(journal->j_commit_request, tid)) {
printk(KERN_EMERG
"%s: error: j_commit_request=%d, tid=%d\n",
__func__, journal->j_commit_request, tid);
}
spin_unlock(&journal->j_state_lock);
#endif
spin_lock(&journal->j_state_lock);
while (tid_gt(tid, journal->j_commit_sequence)) {
jbd_debug(1, "JBD: want %d, j_commit_sequence=%d\n",
tid, journal->j_commit_sequence);
wake_up(&journal->j_wait_commit);
spin_unlock(&journal->j_state_lock);
wait_event(journal->j_wait_done_commit,
!tid_gt(tid, journal->j_commit_sequence));
spin_lock(&journal->j_state_lock);
}
spin_unlock(&journal->j_state_lock);
if (unlikely(is_journal_aborted(journal))) {
printk(KERN_EMERG "journal commit I/O error\n");
err = -EIO;
}
return err;
}
/*
* Log buffer allocation routines:
*/
int journal_next_log_block(journal_t *journal, unsigned long *retp)
{
unsigned long blocknr;
spin_lock(&journal->j_state_lock);
J_ASSERT(journal->j_free > 1);
blocknr = journal->j_head;
journal->j_head++;
journal->j_free--;
if (journal->j_head == journal->j_last)
journal->j_head = journal->j_first;
spin_unlock(&journal->j_state_lock);
return journal_bmap(journal, blocknr, retp);
}
/*
* Conversion of logical to physical block numbers for the journal
*
* On external journals the journal blocks are identity-mapped, so
* this is a no-op. If needed, we can use j_blk_offset - everything is
* ready.
*/
int journal_bmap(journal_t *journal, unsigned long blocknr,
unsigned long *retp)
{
int err = 0;
unsigned long ret;
if (journal->j_inode) {
ret = bmap(journal->j_inode, blocknr);
if (ret)
*retp = ret;
else {
char b[BDEVNAME_SIZE];
printk(KERN_ALERT "%s: journal block not found "
"at offset %lu on %s\n",
__func__,
blocknr,
bdevname(journal->j_dev, b));
err = -EIO;
__journal_abort_soft(journal, err);
}
} else {
*retp = blocknr; /* +journal->j_blk_offset */
}
return err;
}
/*
* We play buffer_head aliasing tricks to write data/metadata blocks to
* the journal without copying their contents, but for journal
* descriptor blocks we do need to generate bona fide buffers.
*
* After the caller of journal_get_descriptor_buffer() has finished modifying
* the buffer's contents they really should run flush_dcache_page(bh->b_page).
* But we don't bother doing that, so there will be coherency problems with
* mmaps of blockdevs which hold live JBD-controlled filesystems.
*/
struct journal_head *journal_get_descriptor_buffer(journal_t *journal)
{
struct buffer_head *bh;
unsigned long blocknr;
int err;
err = journal_next_log_block(journal, &blocknr);
if (err)
return NULL;
bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
lock_buffer(bh);
memset(bh->b_data, 0, journal->j_blocksize);
set_buffer_uptodate(bh);
unlock_buffer(bh);
BUFFER_TRACE(bh, "return this buffer");
return journal_add_journal_head(bh);
}
/*
* Management for journal control blocks: functions to create and
* destroy journal_t structures, and to initialise and read existing
* journal blocks from disk. */
/* First: create and setup a journal_t object in memory. We initialise
* very few fields yet: that has to wait until we have created the
* journal structures from from scratch, or loaded them from disk. */
static journal_t * journal_init_common (void)
{
journal_t *journal;
int err;
journal = kzalloc(sizeof(*journal), GFP_KERNEL);
if (!journal)
goto fail;
init_waitqueue_head(&journal->j_wait_transaction_locked);
init_waitqueue_head(&journal->j_wait_logspace);
init_waitqueue_head(&journal->j_wait_done_commit);
init_waitqueue_head(&journal->j_wait_checkpoint);
init_waitqueue_head(&journal->j_wait_commit);
init_waitqueue_head(&journal->j_wait_updates);
mutex_init(&journal->j_barrier);
mutex_init(&journal->j_checkpoint_mutex);
spin_lock_init(&journal->j_revoke_lock);
spin_lock_init(&journal->j_list_lock);
spin_lock_init(&journal->j_state_lock);
journal->j_commit_interval = (HZ * JBD_DEFAULT_MAX_COMMIT_AGE);
/* The journal is marked for error until we succeed with recovery! */
journal->j_flags = JFS_ABORT;
/* Set up a default-sized revoke table for the new mount. */
err = journal_init_revoke(journal, JOURNAL_REVOKE_DEFAULT_HASH);
if (err) {
kfree(journal);
goto fail;
}
return journal;
fail:
return NULL;
}
/* journal_init_dev and journal_init_inode:
*
* Create a journal structure assigned some fixed set of disk blocks to
* the journal. We don't actually touch those disk blocks yet, but we
* need to set up all of the mapping information to tell the journaling
* system where the journal blocks are.
*
*/
/**
* journal_t * journal_init_dev() - creates and initialises a journal structure
* @bdev: Block device on which to create the journal
* @fs_dev: Device which hold journalled filesystem for this journal.
* @start: Block nr Start of journal.
* @len: Length of the journal in blocks.
* @blocksize: blocksize of journalling device
*
* Returns: a newly created journal_t *
*
* journal_init_dev creates a journal which maps a fixed contiguous
* range of blocks on an arbitrary block device.
*
*/
journal_t * journal_init_dev(struct block_device *bdev,
struct block_device *fs_dev,
int start, int len, int blocksize)
{
journal_t *journal = journal_init_common();
struct buffer_head *bh;
int n;
if (!journal)
return NULL;
/* journal descriptor can store up to n blocks -bzzz */
journal->j_blocksize = blocksize;
n = journal->j_blocksize / sizeof(journal_block_tag_t);
journal->j_wbufsize = n;
journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
if (!journal->j_wbuf) {
printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
__func__);
kfree(journal);
journal = NULL;
goto out;
}
journal->j_dev = bdev;
journal->j_fs_dev = fs_dev;
journal->j_blk_offset = start;
journal->j_maxlen = len;
bh = __getblk(journal->j_dev, start, journal->j_blocksize);
J_ASSERT(bh != NULL);
journal->j_sb_buffer = bh;
journal->j_superblock = (journal_superblock_t *)bh->b_data;
out:
return journal;
}
/**
* journal_t * journal_init_inode () - creates a journal which maps to a inode.
* @inode: An inode to create the journal in
*
* journal_init_inode creates a journal which maps an on-disk inode as
* the journal. The inode must exist already, must support bmap() and
* must have all data blocks preallocated.
*/
journal_t * journal_init_inode (struct inode *inode)
{
struct buffer_head *bh;
journal_t *journal = journal_init_common();
int err;
int n;
unsigned long blocknr;
if (!journal)
return NULL;
journal->j_dev = journal->j_fs_dev = inode->i_sb->s_bdev;
journal->j_inode = inode;
jbd_debug(1,
"journal %p: inode %s/%ld, size %Ld, bits %d, blksize %ld\n",
journal, inode->i_sb->s_id, inode->i_ino,
(long long) inode->i_size,
inode->i_sb->s_blocksize_bits, inode->i_sb->s_blocksize);
journal->j_maxlen = inode->i_size >> inode->i_sb->s_blocksize_bits;
journal->j_blocksize = inode->i_sb->s_blocksize;
/* journal descriptor can store up to n blocks -bzzz */
n = journal->j_blocksize / sizeof(journal_block_tag_t);
journal->j_wbufsize = n;
journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
if (!journal->j_wbuf) {
printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
__func__);
kfree(journal);
return NULL;
}
err = journal_bmap(journal, 0, &blocknr);
/* If that failed, give up */
if (err) {
printk(KERN_ERR "%s: Cannnot locate journal superblock\n",
__func__);
kfree(journal);
return NULL;
}
bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
J_ASSERT(bh != NULL);
journal->j_sb_buffer = bh;
journal->j_superblock = (journal_superblock_t *)bh->b_data;
return journal;
}
/*
* If the journal init or create aborts, we need to mark the journal
* superblock as being NULL to prevent the journal destroy from writing
* back a bogus superblock.
*/
static void journal_fail_superblock (journal_t *journal)
{
struct buffer_head *bh = journal->j_sb_buffer;
brelse(bh);
journal->j_sb_buffer = NULL;
}
/*
* Given a journal_t structure, initialise the various fields for
* startup of a new journaling session. We use this both when creating
* a journal, and after recovering an old journal to reset it for
* subsequent use.
*/
static int journal_reset(journal_t *journal)
{
journal_superblock_t *sb = journal->j_superblock;
unsigned long first, last;
first = be32_to_cpu(sb->s_first);
last = be32_to_cpu(sb->s_maxlen);
journal->j_first = first;
journal->j_last = last;
journal->j_head = first;
journal->j_tail = first;
journal->j_free = last - first;
journal->j_tail_sequence = journal->j_transaction_sequence;
journal->j_commit_sequence = journal->j_transaction_sequence - 1;
journal->j_commit_request = journal->j_commit_sequence;
journal->j_max_transaction_buffers = journal->j_maxlen / 4;
/* Add the dynamic fields and write it to disk. */
journal_update_superblock(journal, 1);
return journal_start_thread(journal);
}
/**
* int journal_create() - Initialise the new journal file
* @journal: Journal to create. This structure must have been initialised
*
* Given a journal_t structure which tells us which disk blocks we can
* use, create a new journal superblock and initialise all of the
* journal fields from scratch.
**/
int journal_create(journal_t *journal)
{
unsigned long blocknr;
struct buffer_head *bh;
journal_superblock_t *sb;
int i, err;
if (journal->j_maxlen < JFS_MIN_JOURNAL_BLOCKS) {
printk (KERN_ERR "Journal length (%d blocks) too short.\n",
journal->j_maxlen);
journal_fail_superblock(journal);
return -EINVAL;
}
if (journal->j_inode == NULL) {
/*
* We don't know what block to start at!
*/
printk(KERN_EMERG
"%s: creation of journal on external device!\n",
__func__);
BUG();
}
/* Zero out the entire journal on disk. We cannot afford to
have any blocks on disk beginning with JFS_MAGIC_NUMBER. */
jbd_debug(1, "JBD: Zeroing out journal blocks...\n");
for (i = 0; i < journal->j_maxlen; i++) {
err = journal_bmap(journal, i, &blocknr);
if (err)
return err;
bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
lock_buffer(bh);
memset (bh->b_data, 0, journal->j_blocksize);
BUFFER_TRACE(bh, "marking dirty");
mark_buffer_dirty(bh);
BUFFER_TRACE(bh, "marking uptodate");
set_buffer_uptodate(bh);
unlock_buffer(bh);
__brelse(bh);
}
sync_blockdev(journal->j_dev);
jbd_debug(1, "JBD: journal cleared.\n");
/* OK, fill in the initial static fields in the new superblock */
sb = journal->j_superblock;
sb->s_header.h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
sb->s_header.h_blocktype = cpu_to_be32(JFS_SUPERBLOCK_V2);
sb->s_blocksize = cpu_to_be32(journal->j_blocksize);
sb->s_maxlen = cpu_to_be32(journal->j_maxlen);
sb->s_first = cpu_to_be32(1);
journal->j_transaction_sequence = 1;
journal->j_flags &= ~JFS_ABORT;
journal->j_format_version = 2;
return journal_reset(journal);
}
/**
* void journal_update_superblock() - Update journal sb on disk.
* @journal: The journal to update.
* @wait: Set to '0' if you don't want to wait for IO completion.
*
* Update a journal's dynamic superblock fields and write it to disk,
* optionally waiting for the IO to complete.
*/
void journal_update_superblock(journal_t *journal, int wait)
{
journal_superblock_t *sb = journal->j_superblock;
struct buffer_head *bh = journal->j_sb_buffer;
/*
* As a special case, if the on-disk copy is already marked as needing
* no recovery (s_start == 0) and there are no outstanding transactions
* in the filesystem, then we can safely defer the superblock update
* until the next commit by setting JFS_FLUSHED. This avoids
* attempting a write to a potential-readonly device.
*/
if (sb->s_start == 0 && journal->j_tail_sequence ==
journal->j_transaction_sequence) {
jbd_debug(1,"JBD: Skipping superblock update on recovered sb "
"(start %ld, seq %d, errno %d)\n",
journal->j_tail, journal->j_tail_sequence,
journal->j_errno);
goto out;
}
spin_lock(&journal->j_state_lock);
jbd_debug(1,"JBD: updating superblock (start %ld, seq %d, errno %d)\n",
journal->j_tail, journal->j_tail_sequence, journal->j_errno);
sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
sb->s_start = cpu_to_be32(journal->j_tail);
sb->s_errno = cpu_to_be32(journal->j_errno);
spin_unlock(&journal->j_state_lock);
BUFFER_TRACE(bh, "marking dirty");
mark_buffer_dirty(bh);
if (wait)
sync_dirty_buffer(bh);
else
ll_rw_block(SWRITE, 1, &bh);
out:
/* If we have just flushed the log (by marking s_start==0), then
* any future commit will have to be careful to update the
* superblock again to re-record the true start of the log. */
spin_lock(&journal->j_state_lock);
if (sb->s_start)
journal->j_flags &= ~JFS_FLUSHED;
else
journal->j_flags |= JFS_FLUSHED;
spin_unlock(&journal->j_state_lock);
}
/*
* Read the superblock for a given journal, performing initial
* validation of the format.
*/
static int journal_get_superblock(journal_t *journal)
{
struct buffer_head *bh;
journal_superblock_t *sb;
int err = -EIO;
bh = journal->j_sb_buffer;
J_ASSERT(bh != NULL);
if (!buffer_uptodate(bh)) {
ll_rw_block(READ, 1, &bh);
wait_on_buffer(bh);
if (!buffer_uptodate(bh)) {
printk (KERN_ERR
"JBD: IO error reading journal superblock\n");
goto out;
}
}
sb = journal->j_superblock;
err = -EINVAL;
if (sb->s_header.h_magic != cpu_to_be32(JFS_MAGIC_NUMBER) ||
sb->s_blocksize != cpu_to_be32(journal->j_blocksize)) {
printk(KERN_WARNING "JBD: no valid journal superblock found\n");
goto out;
}
switch(be32_to_cpu(sb->s_header.h_blocktype)) {
case JFS_SUPERBLOCK_V1:
journal->j_format_version = 1;
break;
case JFS_SUPERBLOCK_V2:
journal->j_format_version = 2;
break;
default:
printk(KERN_WARNING "JBD: unrecognised superblock format ID\n");
goto out;
}
if (be32_to_cpu(sb->s_maxlen) < journal->j_maxlen)
journal->j_maxlen = be32_to_cpu(sb->s_maxlen);
else if (be32_to_cpu(sb->s_maxlen) > journal->j_maxlen) {
printk (KERN_WARNING "JBD: journal file too short\n");
goto out;
}
return 0;
out:
journal_fail_superblock(journal);
return err;
}
/*
* Load the on-disk journal superblock and read the key fields into the
* journal_t.
*/
static int load_superblock(journal_t *journal)
{
int err;
journal_superblock_t *sb;
err = journal_get_superblock(journal);
if (err)
return err;
sb = journal->j_superblock;
journal->j_tail_sequence = be32_to_cpu(sb->s_sequence);
journal->j_tail = be32_to_cpu(sb->s_start);
journal->j_first = be32_to_cpu(sb->s_first);
journal->j_last = be32_to_cpu(sb->s_maxlen);
journal->j_errno = be32_to_cpu(sb->s_errno);
return 0;
}
/**
* int journal_load() - Read journal from disk.
* @journal: Journal to act on.
*
* Given a journal_t structure which tells us which disk blocks contain
* a journal, read the journal from disk to initialise the in-memory
* structures.
*/
int journal_load(journal_t *journal)
{
int err;
journal_superblock_t *sb;
err = load_superblock(journal);
if (err)
return err;
sb = journal->j_superblock;
/* If this is a V2 superblock, then we have to check the
* features flags on it. */
if (journal->j_format_version >= 2) {
if ((sb->s_feature_ro_compat &
~cpu_to_be32(JFS_KNOWN_ROCOMPAT_FEATURES)) ||
(sb->s_feature_incompat &
~cpu_to_be32(JFS_KNOWN_INCOMPAT_FEATURES))) {
printk (KERN_WARNING
"JBD: Unrecognised features on journal\n");
return -EINVAL;
}
}
/* Let the recovery code check whether it needs to recover any
* data from the journal. */
if (journal_recover(journal))
goto recovery_error;
/* OK, we've finished with the dynamic journal bits:
* reinitialise the dynamic contents of the superblock in memory
* and reset them on disk. */
if (journal_reset(journal))
goto recovery_error;
journal->j_flags &= ~JFS_ABORT;
journal->j_flags |= JFS_LOADED;
return 0;
recovery_error:
printk (KERN_WARNING "JBD: recovery failed\n");
return -EIO;
}
/**
* void journal_destroy() - Release a journal_t structure.
* @journal: Journal to act on.
*
* Release a journal_t structure once it is no longer in use by the
* journaled object.
*/
void journal_destroy(journal_t *journal)
{
/* Wait for the commit thread to wake up and die. */
journal_kill_thread(journal);
/* Force a final log commit */
if (journal->j_running_transaction)
journal_commit_transaction(journal);
/* Force any old transactions to disk */
/* Totally anal locking here... */
spin_lock(&journal->j_list_lock);
while (journal->j_checkpoint_transactions != NULL) {
spin_unlock(&journal->j_list_lock);
log_do_checkpoint(journal);
spin_lock(&journal->j_list_lock);
}
J_ASSERT(journal->j_running_transaction == NULL);
J_ASSERT(journal->j_committing_transaction == NULL);
J_ASSERT(journal->j_checkpoint_transactions == NULL);
spin_unlock(&journal->j_list_lock);
/* We can now mark the journal as empty. */
journal->j_tail = 0;
journal->j_tail_sequence = ++journal->j_transaction_sequence;
if (journal->j_sb_buffer) {
journal_update_superblock(journal, 1);
brelse(journal->j_sb_buffer);
}
if (journal->j_inode)
iput(journal->j_inode);
if (journal->j_revoke)
journal_destroy_revoke(journal);
kfree(journal->j_wbuf);
kfree(journal);
}
/**
*int journal_check_used_features () - Check if features specified are used.
* @journal: Journal to check.
* @compat: bitmask of compatible features
* @ro: bitmask of features that force read-only mount
* @incompat: bitmask of incompatible features
*
* Check whether the journal uses all of a given set of
* features. Return true (non-zero) if it does.
**/
int journal_check_used_features (journal_t *journal, unsigned long compat,
unsigned long ro, unsigned long incompat)
{
journal_superblock_t *sb;
if (!compat && !ro && !incompat)
return 1;
if (journal->j_format_version == 1)
return 0;
sb = journal->j_superblock;
if (((be32_to_cpu(sb->s_feature_compat) & compat) == compat) &&
((be32_to_cpu(sb->s_feature_ro_compat) & ro) == ro) &&
((be32_to_cpu(sb->s_feature_incompat) & incompat) == incompat))
return 1;
return 0;
}
/**
* int journal_check_available_features() - Check feature set in journalling layer
* @journal: Journal to check.
* @compat: bitmask of compatible features
* @ro: bitmask of features that force read-only mount
* @incompat: bitmask of incompatible features
*
* Check whether the journaling code supports the use of
* all of a given set of features on this journal. Return true
* (non-zero) if it can. */
int journal_check_available_features (journal_t *journal, unsigned long compat,
unsigned long ro, unsigned long incompat)
{
journal_superblock_t *sb;
if (!compat && !ro && !incompat)
return 1;
sb = journal->j_superblock;
/* We can support any known requested features iff the
* superblock is in version 2. Otherwise we fail to support any
* extended sb features. */
if (journal->j_format_version != 2)
return 0;
if ((compat & JFS_KNOWN_COMPAT_FEATURES) == compat &&
(ro & JFS_KNOWN_ROCOMPAT_FEATURES) == ro &&
(incompat & JFS_KNOWN_INCOMPAT_FEATURES) == incompat)
return 1;
return 0;
}
/**
* int journal_set_features () - Mark a given journal feature in the superblock
* @journal: Journal to act on.
* @compat: bitmask of compatible features
* @ro: bitmask of features that force read-only mount
* @incompat: bitmask of incompatible features
*
* Mark a given journal feature as present on the
* superblock. Returns true if the requested features could be set.
*
*/
int journal_set_features (journal_t *journal, unsigned long compat,
unsigned long ro, unsigned long incompat)
{
journal_superblock_t *sb;
if (journal_check_used_features(journal, compat, ro, incompat))
return 1;
if (!journal_check_available_features(journal, compat, ro, incompat))
return 0;
jbd_debug(1, "Setting new features 0x%lx/0x%lx/0x%lx\n",
compat, ro, incompat);
sb = journal->j_superblock;
sb->s_feature_compat |= cpu_to_be32(compat);
sb->s_feature_ro_compat |= cpu_to_be32(ro);
sb->s_feature_incompat |= cpu_to_be32(incompat);
return 1;
}
/**
* int journal_update_format () - Update on-disk journal structure.
* @journal: Journal to act on.
*
* Given an initialised but unloaded journal struct, poke about in the
* on-disk structure to update it to the most recent supported version.
*/
int journal_update_format (journal_t *journal)
{
journal_superblock_t *sb;
int err;
err = journal_get_superblock(journal);
if (err)
return err;
sb = journal->j_superblock;
switch (be32_to_cpu(sb->s_header.h_blocktype)) {
case JFS_SUPERBLOCK_V2:
return 0;
case JFS_SUPERBLOCK_V1:
return journal_convert_superblock_v1(journal, sb);
default:
break;
}
return -EINVAL;
}
static int journal_convert_superblock_v1(journal_t *journal,
journal_superblock_t *sb)
{
int offset, blocksize;
struct buffer_head *bh;
printk(KERN_WARNING
"JBD: Converting superblock from version 1 to 2.\n");
/* Pre-initialise new fields to zero */
offset = ((char *) &(sb->s_feature_compat)) - ((char *) sb);
blocksize = be32_to_cpu(sb->s_blocksize);
memset(&sb->s_feature_compat, 0, blocksize-offset);
sb->s_nr_users = cpu_to_be32(1);
sb->s_header.h_blocktype = cpu_to_be32(JFS_SUPERBLOCK_V2);
journal->j_format_version = 2;
bh = journal->j_sb_buffer;
BUFFER_TRACE(bh, "marking dirty");
mark_buffer_dirty(bh);
sync_dirty_buffer(bh);
return 0;
}
/**
* int journal_flush () - Flush journal
* @journal: Journal to act on.
*
* Flush all data for a given journal to disk and empty the journal.
* Filesystems can use this when remounting readonly to ensure that
* recovery does not need to happen on remount.
*/
int journal_flush(journal_t *journal)
{
int err = 0;
transaction_t *transaction = NULL;
unsigned long old_tail;
spin_lock(&journal->j_state_lock);
/* Force everything buffered to the log... */
if (journal->j_running_transaction) {
transaction = journal->j_running_transaction;
__log_start_commit(journal, transaction->t_tid);
} else if (journal->j_committing_transaction)
transaction = journal->j_committing_transaction;
/* Wait for the log commit to complete... */
if (transaction) {
tid_t tid = transaction->t_tid;
spin_unlock(&journal->j_state_lock);
log_wait_commit(journal, tid);
} else {
spin_unlock(&journal->j_state_lock);
}
/* ...and flush everything in the log out to disk. */
spin_lock(&journal->j_list_lock);
while (!err && journal->j_checkpoint_transactions != NULL) {
spin_unlock(&journal->j_list_lock);
err = log_do_checkpoint(journal);
spin_lock(&journal->j_list_lock);
}
spin_unlock(&journal->j_list_lock);
cleanup_journal_tail(journal);
/* Finally, mark the journal as really needing no recovery.
* This sets s_start==0 in the underlying superblock, which is
* the magic code for a fully-recovered superblock. Any future
* commits of data to the journal will restore the current
* s_start value. */
spin_lock(&journal->j_state_lock);
old_tail = journal->j_tail;
journal->j_tail = 0;
spin_unlock(&journal->j_state_lock);
journal_update_superblock(journal, 1);
spin_lock(&journal->j_state_lock);
journal->j_tail = old_tail;
J_ASSERT(!journal->j_running_transaction);
J_ASSERT(!journal->j_committing_transaction);
J_ASSERT(!journal->j_checkpoint_transactions);
J_ASSERT(journal->j_head == journal->j_tail);
J_ASSERT(journal->j_tail_sequence == journal->j_transaction_sequence);
spin_unlock(&journal->j_state_lock);
return err;
}
/**
* int journal_wipe() - Wipe journal contents
* @journal: Journal to act on.
* @write: flag (see below)
*
* Wipe out all of the contents of a journal, safely. This will produce
* a warning if the journal contains any valid recovery information.
* Must be called between journal_init_*() and journal_load().
*
* If 'write' is non-zero, then we wipe out the journal on disk; otherwise
* we merely suppress recovery.
*/
int journal_wipe(journal_t *journal, int write)
{
journal_superblock_t *sb;
int err = 0;
J_ASSERT (!(journal->j_flags & JFS_LOADED));
err = load_superblock(journal);
if (err)
return err;
sb = journal->j_superblock;
if (!journal->j_tail)
goto no_recovery;
printk (KERN_WARNING "JBD: %s recovery information on journal\n",
write ? "Clearing" : "Ignoring");
err = journal_skip_recovery(journal);
if (write)
journal_update_superblock(journal, 1);
no_recovery:
return err;
}
/*
* journal_dev_name: format a character string to describe on what
* device this journal is present.
*/
static const char *journal_dev_name(journal_t *journal, char *buffer)
{
struct block_device *bdev;
if (journal->j_inode)
bdev = journal->j_inode->i_sb->s_bdev;
else
bdev = journal->j_dev;
return bdevname(bdev, buffer);
}
/*
* Journal abort has very specific semantics, which we describe
* for journal abort.
*
* Two internal function, which provide abort to te jbd layer
* itself are here.
*/
/*
* Quick version for internal journal use (doesn't lock the journal).
* Aborts hard --- we mark the abort as occurred, but do _nothing_ else,
* and don't attempt to make any other journal updates.
*/
static void __journal_abort_hard(journal_t *journal)
{
transaction_t *transaction;
char b[BDEVNAME_SIZE];
if (journal->j_flags & JFS_ABORT)
return;
printk(KERN_ERR "Aborting journal on device %s.\n",
journal_dev_name(journal, b));
spin_lock(&journal->j_state_lock);
journal->j_flags |= JFS_ABORT;
transaction = journal->j_running_transaction;
if (transaction)
__log_start_commit(journal, transaction->t_tid);
spin_unlock(&journal->j_state_lock);
}
/* Soft abort: record the abort error status in the journal superblock,
* but don't do any other IO. */
static void __journal_abort_soft (journal_t *journal, int errno)
{
if (journal->j_flags & JFS_ABORT)
return;
if (!journal->j_errno)
journal->j_errno = errno;
__journal_abort_hard(journal);
if (errno)
journal_update_superblock(journal, 1);
}
/**
* void journal_abort () - Shutdown the journal immediately.
* @journal: the journal to shutdown.
* @errno: an error number to record in the journal indicating
* the reason for the shutdown.
*
* Perform a complete, immediate shutdown of the ENTIRE
* journal (not of a single transaction). This operation cannot be
* undone without closing and reopening the journal.
*
* The journal_abort function is intended to support higher level error
* recovery mechanisms such as the ext2/ext3 remount-readonly error
* mode.
*
* Journal abort has very specific semantics. Any existing dirty,
* unjournaled buffers in the main filesystem will still be written to
* disk by bdflush, but the journaling mechanism will be suspended
* immediately and no further transaction commits will be honoured.
*
* Any dirty, journaled buffers will be written back to disk without
* hitting the journal. Atomicity cannot be guaranteed on an aborted
* filesystem, but we _do_ attempt to leave as much data as possible
* behind for fsck to use for cleanup.
*
* Any attempt to get a new transaction handle on a journal which is in
* ABORT state will just result in an -EROFS error return. A
* journal_stop on an existing handle will return -EIO if we have
* entered abort state during the update.
*
* Recursive transactions are not disturbed by journal abort until the
* final journal_stop, which will receive the -EIO error.
*
* Finally, the journal_abort call allows the caller to supply an errno
* which will be recorded (if possible) in the journal superblock. This
* allows a client to record failure conditions in the middle of a
* transaction without having to complete the transaction to record the
* failure to disk. ext3_error, for example, now uses this
* functionality.
*
* Errors which originate from within the journaling layer will NOT
* supply an errno; a null errno implies that absolutely no further
* writes are done to the journal (unless there are any already in
* progress).
*
*/
void journal_abort(journal_t *journal, int errno)
{
__journal_abort_soft(journal, errno);
}
/**
* int journal_errno () - returns the journal's error state.
* @journal: journal to examine.
*
* This is the errno numbet set with journal_abort(), the last
* time the journal was mounted - if the journal was stopped
* without calling abort this will be 0.
*
* If the journal has been aborted on this mount time -EROFS will
* be returned.
*/
int journal_errno(journal_t *journal)
{
int err;
spin_lock(&journal->j_state_lock);
if (journal->j_flags & JFS_ABORT)
err = -EROFS;
else
err = journal->j_errno;
spin_unlock(&journal->j_state_lock);
return err;
}
/**
* int journal_clear_err () - clears the journal's error state
* @journal: journal to act on.
*
* An error must be cleared or Acked to take a FS out of readonly
* mode.
*/
int journal_clear_err(journal_t *journal)
{
int err = 0;
spin_lock(&journal->j_state_lock);
if (journal->j_flags & JFS_ABORT)
err = -EROFS;
else
journal->j_errno = 0;
spin_unlock(&journal->j_state_lock);
return err;
}
/**
* void journal_ack_err() - Ack journal err.
* @journal: journal to act on.
*
* An error must be cleared or Acked to take a FS out of readonly
* mode.
*/
void journal_ack_err(journal_t *journal)
{
spin_lock(&journal->j_state_lock);
if (journal->j_errno)
journal->j_flags |= JFS_ACK_ERR;
spin_unlock(&journal->j_state_lock);
}
int journal_blocks_per_page(struct inode *inode)
{
return 1 << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
}
/*
* Journal_head storage management
*/
static struct kmem_cache *journal_head_cache;
#ifdef CONFIG_JBD_DEBUG
static atomic_t nr_journal_heads = ATOMIC_INIT(0);
#endif
static int journal_init_journal_head_cache(void)
{
int retval;
J_ASSERT(journal_head_cache == NULL);
journal_head_cache = kmem_cache_create("journal_head",
sizeof(struct journal_head),
0, /* offset */
SLAB_TEMPORARY, /* flags */
NULL); /* ctor */
retval = 0;
if (!journal_head_cache) {
retval = -ENOMEM;
printk(KERN_EMERG "JBD: no memory for journal_head cache\n");
}
return retval;
}
static void journal_destroy_journal_head_cache(void)
{
if (journal_head_cache) {
kmem_cache_destroy(journal_head_cache);
journal_head_cache = NULL;
}
}
/*
* journal_head splicing and dicing
*/
static struct journal_head *journal_alloc_journal_head(void)
{
struct journal_head *ret;
static unsigned long last_warning;
#ifdef CONFIG_JBD_DEBUG
atomic_inc(&nr_journal_heads);
#endif
ret = kmem_cache_alloc(journal_head_cache, GFP_NOFS);
if (ret == NULL) {
jbd_debug(1, "out of memory for journal_head\n");
if (time_after(jiffies, last_warning + 5*HZ)) {
printk(KERN_NOTICE "ENOMEM in %s, retrying.\n",
__func__);
last_warning = jiffies;
}
while (ret == NULL) {
yield();
ret = kmem_cache_alloc(journal_head_cache, GFP_NOFS);
}
}
return ret;
}
static void journal_free_journal_head(struct journal_head *jh)
{
#ifdef CONFIG_JBD_DEBUG
atomic_dec(&nr_journal_heads);
memset(jh, JBD_POISON_FREE, sizeof(*jh));
#endif
kmem_cache_free(journal_head_cache, jh);
}
/*
* A journal_head is attached to a buffer_head whenever JBD has an
* interest in the buffer.
*
* Whenever a buffer has an attached journal_head, its ->b_state:BH_JBD bit
* is set. This bit is tested in core kernel code where we need to take
* JBD-specific actions. Testing the zeroness of ->b_private is not reliable
* there.
*
* When a buffer has its BH_JBD bit set, its ->b_count is elevated by one.
*
* When a buffer has its BH_JBD bit set it is immune from being released by
* core kernel code, mainly via ->b_count.
*
* A journal_head may be detached from its buffer_head when the journal_head's
* b_transaction, b_cp_transaction and b_next_transaction pointers are NULL.
* Various places in JBD call journal_remove_journal_head() to indicate that the
* journal_head can be dropped if needed.
*
* Various places in the kernel want to attach a journal_head to a buffer_head
* _before_ attaching the journal_head to a transaction. To protect the
* journal_head in this situation, journal_add_journal_head elevates the
* journal_head's b_jcount refcount by one. The caller must call
* journal_put_journal_head() to undo this.
*
* So the typical usage would be:
*
* (Attach a journal_head if needed. Increments b_jcount)
* struct journal_head *jh = journal_add_journal_head(bh);
* ...
* jh->b_transaction = xxx;
* journal_put_journal_head(jh);
*
* Now, the journal_head's b_jcount is zero, but it is safe from being released
* because it has a non-zero b_transaction.
*/
/*
* Give a buffer_head a journal_head.
*
* Doesn't need the journal lock.
* May sleep.
*/
struct journal_head *journal_add_journal_head(struct buffer_head *bh)
{
struct journal_head *jh;
struct journal_head *new_jh = NULL;
repeat:
if (!buffer_jbd(bh)) {
new_jh = journal_alloc_journal_head();
memset(new_jh, 0, sizeof(*new_jh));
}
jbd_lock_bh_journal_head(bh);
if (buffer_jbd(bh)) {
jh = bh2jh(bh);
} else {
J_ASSERT_BH(bh,
(atomic_read(&bh->b_count) > 0) ||
(bh->b_page && bh->b_page->mapping));
if (!new_jh) {
jbd_unlock_bh_journal_head(bh);
goto repeat;
}
jh = new_jh;
new_jh = NULL; /* We consumed it */
set_buffer_jbd(bh);
bh->b_private = jh;
jh->b_bh = bh;
get_bh(bh);
BUFFER_TRACE(bh, "added journal_head");
}
jh->b_jcount++;
jbd_unlock_bh_journal_head(bh);
if (new_jh)
journal_free_journal_head(new_jh);
return bh->b_private;
}
/*
* Grab a ref against this buffer_head's journal_head. If it ended up not
* having a journal_head, return NULL
*/
struct journal_head *journal_grab_journal_head(struct buffer_head *bh)
{
struct journal_head *jh = NULL;
jbd_lock_bh_journal_head(bh);
if (buffer_jbd(bh)) {
jh = bh2jh(bh);
jh->b_jcount++;
}
jbd_unlock_bh_journal_head(bh);
return jh;
}
static void __journal_remove_journal_head(struct buffer_head *bh)
{
struct journal_head *jh = bh2jh(bh);
J_ASSERT_JH(jh, jh->b_jcount >= 0);
get_bh(bh);
if (jh->b_jcount == 0) {
if (jh->b_transaction == NULL &&
jh->b_next_transaction == NULL &&
jh->b_cp_transaction == NULL) {
J_ASSERT_JH(jh, jh->b_jlist == BJ_None);
J_ASSERT_BH(bh, buffer_jbd(bh));
J_ASSERT_BH(bh, jh2bh(jh) == bh);
BUFFER_TRACE(bh, "remove journal_head");
if (jh->b_frozen_data) {
printk(KERN_WARNING "%s: freeing "
"b_frozen_data\n",
__func__);
jbd_free(jh->b_frozen_data, bh->b_size);
}
if (jh->b_committed_data) {
printk(KERN_WARNING "%s: freeing "
"b_committed_data\n",
__func__);
jbd_free(jh->b_committed_data, bh->b_size);
}
bh->b_private = NULL;
jh->b_bh = NULL; /* debug, really */
clear_buffer_jbd(bh);
__brelse(bh);
journal_free_journal_head(jh);
} else {
BUFFER_TRACE(bh, "journal_head was locked");
}
}
}
/*
* journal_remove_journal_head(): if the buffer isn't attached to a transaction
* and has a zero b_jcount then remove and release its journal_head. If we did
* see that the buffer is not used by any transaction we also "logically"
* decrement ->b_count.
*
* We in fact take an additional increment on ->b_count as a convenience,
* because the caller usually wants to do additional things with the bh
* after calling here.
* The caller of journal_remove_journal_head() *must* run __brelse(bh) at some
* time. Once the caller has run __brelse(), the buffer is eligible for
* reaping by try_to_free_buffers().
*/
void journal_remove_journal_head(struct buffer_head *bh)
{
jbd_lock_bh_journal_head(bh);
__journal_remove_journal_head(bh);
jbd_unlock_bh_journal_head(bh);
}
/*
* Drop a reference on the passed journal_head. If it fell to zero then try to
* release the journal_head from the buffer_head.
*/
void journal_put_journal_head(struct journal_head *jh)
{
struct buffer_head *bh = jh2bh(jh);
jbd_lock_bh_journal_head(bh);
J_ASSERT_JH(jh, jh->b_jcount > 0);
--jh->b_jcount;
if (!jh->b_jcount && !jh->b_transaction) {
__journal_remove_journal_head(bh);
__brelse(bh);
}
jbd_unlock_bh_journal_head(bh);
}
/*
* debugfs tunables
*/
#ifdef CONFIG_JBD_DEBUG
u8 journal_enable_debug __read_mostly;
EXPORT_SYMBOL(journal_enable_debug);
static struct dentry *jbd_debugfs_dir;
static struct dentry *jbd_debug;
static void __init jbd_create_debugfs_entry(void)
{
jbd_debugfs_dir = debugfs_create_dir("jbd", NULL);
if (jbd_debugfs_dir)
jbd_debug = debugfs_create_u8("jbd-debug", S_IRUGO,
jbd_debugfs_dir,
&journal_enable_debug);
}
static void __exit jbd_remove_debugfs_entry(void)
{
debugfs_remove(jbd_debug);
debugfs_remove(jbd_debugfs_dir);
}
#else
static inline void jbd_create_debugfs_entry(void)
{
}
static inline void jbd_remove_debugfs_entry(void)
{
}
#endif
struct kmem_cache *jbd_handle_cache;
static int __init journal_init_handle_cache(void)
{
jbd_handle_cache = kmem_cache_create("journal_handle",
sizeof(handle_t),
0, /* offset */
SLAB_TEMPORARY, /* flags */
NULL); /* ctor */
if (jbd_handle_cache == NULL) {
printk(KERN_EMERG "JBD: failed to create handle cache\n");
return -ENOMEM;
}
return 0;
}
static void journal_destroy_handle_cache(void)
{
if (jbd_handle_cache)
kmem_cache_destroy(jbd_handle_cache);
}
/*
* Module startup and shutdown
*/
static int __init journal_init_caches(void)
{
int ret;
ret = journal_init_revoke_caches();
if (ret == 0)
ret = journal_init_journal_head_cache();
if (ret == 0)
ret = journal_init_handle_cache();
return ret;
}
static void journal_destroy_caches(void)
{
journal_destroy_revoke_caches();
journal_destroy_journal_head_cache();
journal_destroy_handle_cache();
}
static int __init journal_init(void)
{
int ret;
BUILD_BUG_ON(sizeof(struct journal_superblock_s) != 1024);
ret = journal_init_caches();
if (ret != 0)
journal_destroy_caches();
jbd_create_debugfs_entry();
return ret;
}
static void __exit journal_exit(void)
{
#ifdef CONFIG_JBD_DEBUG
int n = atomic_read(&nr_journal_heads);
if (n)
printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
#endif
jbd_remove_debugfs_entry();
journal_destroy_caches();
}
MODULE_LICENSE("GPL");
module_init(journal_init);
module_exit(journal_exit);
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