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/*
* linux/fs/transaction.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 transaction handling code; part of the ext2fs
* journaling system.
*
* This file manages transactions (compound commits managed by the
* journaling code) and handles (individual atomic operations by the
* filesystem).
*/
#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/timer.h>
#include <linux/smp_lock.h>
#include <linux/mm.h>
extern spinlock_t journal_datalist_lock;
/*
* get_transaction: obtain a new transaction_t object.
*
* Simply allocate and initialise a new transaction. Create it in
* RUNNING state and add it to the current journal (which should not
* have an existing running transaction: we only make a new transaction
* once we have started to commit the old one).
*
* Preconditions:
* The journal MUST be locked. We don't perform atomic mallocs on the
* new transaction and we can't block without protecting against other
* processes trying to touch the journal while it is in transition.
*/
static transaction_t * get_transaction (journal_t * journal, int is_try)
{
transaction_t * transaction;
transaction = jbd_kmalloc (sizeof (transaction_t), GFP_NOFS);
if (!transaction)
return NULL;
memset (transaction, 0, sizeof (transaction_t));
transaction->t_journal = journal;
transaction->t_state = T_RUNNING;
transaction->t_tid = journal->j_transaction_sequence++;
transaction->t_expires = jiffies + journal->j_commit_interval;
/* Set up the commit timer for the new transaction. */
J_ASSERT (!journal->j_commit_timer_active);
journal->j_commit_timer_active = 1;
journal->j_commit_timer->expires = transaction->t_expires;
add_timer(journal->j_commit_timer);
J_ASSERT (journal->j_running_transaction == NULL);
journal->j_running_transaction = transaction;
return transaction;
}
/*
* Handle management.
*
* A handle_t is an object which represents a single atomic update to a
* filesystem, and which tracks all of the modifications which form part
* of that one update.
*/
/*
* start_this_handle: Given a handle, deal with any locking or stalling
* needed to make sure that there is enough journal space for the handle
* to begin. Attach the handle to a transaction and set up the
* transaction's buffer credits.
*/
static int start_this_handle(journal_t *journal, handle_t *handle)
{
transaction_t *transaction;
int needed;
int nblocks = handle->h_buffer_credits;
jbd_debug(3, "New handle %p going live.\n", handle);
repeat:
lock_journal(journal);
repeat_locked:
if (is_journal_aborted(journal) ||
(journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) {
unlock_journal(journal);
return -EROFS;
}
/* Wait on the journal's transaction barrier if necessary */
if (journal->j_barrier_count) {
unlock_journal(journal);
sleep_on(&journal->j_wait_transaction_locked);
goto repeat;
}
if (!journal->j_running_transaction)
get_transaction(journal, 0);
/* @@@ Error? */
J_ASSERT(journal->j_running_transaction);
transaction = journal->j_running_transaction;
/* If the current transaction is locked down for commit, wait
* for the lock to be released. */
if (transaction->t_state == T_LOCKED) {
unlock_journal(journal);
jbd_debug(3, "Handle %p stalling...\n", handle);
sleep_on(&journal->j_wait_transaction_locked);
goto repeat;
}
/* If there is not enough space left in the log to write all
* potential buffers requested by this operation, we need to
* stall pending a log checkpoint to free some more log
* space. */
needed = transaction->t_outstanding_credits + nblocks;
if (needed > journal->j_max_transaction_buffers) {
/* If the current transaction is already too large, then
* start to commit it: we can then go back and attach
* this handle to a new transaction. */
jbd_debug(2, "Handle %p starting new commit...\n", handle);
log_start_commit(journal, transaction);
unlock_journal(journal);
sleep_on(&journal->j_wait_transaction_locked);
lock_journal(journal);
goto repeat_locked;
}
/*
* The commit code assumes that it can get enough log space
* without forcing a checkpoint. This is *critical* for
* correctness: a checkpoint of a buffer which is also
* associated with a committing transaction creates a deadlock,
* so commit simply cannot force through checkpoints.
*
* We must therefore ensure the necessary space in the journal
* *before* starting to dirty potentially checkpointed buffers
* in the new transaction.
*
* The worst part is, any transaction currently committing can
* reduce the free space arbitrarily. Be careful to account for
* those buffers when checkpointing.
*/
/*
* @@@ AKPM: This seems rather over-defensive. We're giving commit
* a _lot_ of headroom: 1/4 of the journal plus the size of
* the committing transaction. Really, we only need to give it
* committing_transaction->t_outstanding_credits plus "enough" for
* the log control blocks.
* Also, this test is inconsitent with the matching one in
* journal_extend().
*/
needed = journal->j_max_transaction_buffers;
if (journal->j_committing_transaction)
needed += journal->j_committing_transaction->
t_outstanding_credits;
if (log_space_left(journal) < needed) {
jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
log_wait_for_space(journal, needed);
goto repeat_locked;
}
/* OK, account for the buffers that this operation expects to
* use and add the handle to the running transaction. */
handle->h_transaction = transaction;
transaction->t_outstanding_credits += nblocks;
transaction->t_updates++;
transaction->t_handle_count++;
jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
handle, nblocks, transaction->t_outstanding_credits,
log_space_left(journal));
unlock_journal(journal);
return 0;
}
/*
* Obtain a new handle.
*
* We make sure that the transaction can guarantee at least nblocks of
* modified buffers in the log. We block until the log can guarantee
* that much space.
*
* This function is visible to journal users (like ext2fs), so is not
* called with the journal already locked.
*
* Return a pointer to a newly allocated handle, or NULL on failure
*/
handle_t *journal_start(journal_t *journal, int nblocks)
{
handle_t *handle = journal_current_handle();
int err;
if (!journal)
return ERR_PTR(-EROFS);
if (handle) {
J_ASSERT(handle->h_transaction->t_journal == journal);
handle->h_ref++;
return handle;
}
handle = jbd_kmalloc(sizeof (handle_t), GFP_NOFS);
if (!handle)
return ERR_PTR(-ENOMEM);
memset (handle, 0, sizeof (handle_t));
handle->h_buffer_credits = nblocks;
handle->h_ref = 1;
current->journal_info = handle;
err = start_this_handle(journal, handle);
if (err < 0) {
kfree(handle);
current->journal_info = NULL;
return ERR_PTR(err);
}
return handle;
}
/*
* Return zero on success
*/
static int try_start_this_handle(journal_t *journal, handle_t *handle)
{
transaction_t *transaction;
int needed;
int nblocks = handle->h_buffer_credits;
int ret = 0;
jbd_debug(3, "New handle %p maybe going live.\n", handle);
lock_journal(journal);
if (is_journal_aborted(journal) ||
(journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) {
ret = -EROFS;
goto fail_unlock;
}
if (journal->j_barrier_count)
goto fail_unlock;
if (!journal->j_running_transaction && get_transaction(journal, 1) == 0)
goto fail_unlock;
transaction = journal->j_running_transaction;
if (transaction->t_state == T_LOCKED)
goto fail_unlock;
needed = transaction->t_outstanding_credits + nblocks;
/* We could run log_start_commit here */
if (needed > journal->j_max_transaction_buffers)
goto fail_unlock;
needed = journal->j_max_transaction_buffers;
if (journal->j_committing_transaction)
needed += journal->j_committing_transaction->
t_outstanding_credits;
if (log_space_left(journal) < needed)
goto fail_unlock;
handle->h_transaction = transaction;
transaction->t_outstanding_credits += nblocks;
transaction->t_updates++;
jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
handle, nblocks, transaction->t_outstanding_credits,
log_space_left(journal));
unlock_journal(journal);
return 0;
fail_unlock:
unlock_journal(journal);
if (ret >= 0)
ret = -1;
return ret;
}
/*
* Try to start a handle, but non-blockingly. If we weren't able
* to, return an ERR_PTR value.
*/
handle_t *journal_try_start(journal_t *journal, int nblocks)
{
handle_t *handle = journal_current_handle();
int err;
if (!journal)
return ERR_PTR(-EROFS);
if (handle) {
jbd_debug(4, "h_ref %d -> %d\n",
handle->h_ref,
handle->h_ref + 1);
J_ASSERT(handle->h_transaction->t_journal == journal);
if (is_handle_aborted(handle))
return ERR_PTR(-EIO);
handle->h_ref++;
return handle;
} else {
jbd_debug(4, "no current transaction\n");
}
if (is_journal_aborted(journal))
return ERR_PTR(-EIO);
handle = jbd_kmalloc(sizeof (handle_t), GFP_NOFS);
if (!handle)
return ERR_PTR(-ENOMEM);
memset (handle, 0, sizeof (handle_t));
handle->h_buffer_credits = nblocks;
handle->h_ref = 1;
current->journal_info = handle;
err = try_start_this_handle(journal, handle);
if (err < 0) {
kfree(handle);
current->journal_info = NULL;
return ERR_PTR(err);
}
return handle;
}
/*
* journal_extend: extend buffer credits.
*
* Some transactions, such as large extends and truncates, can be done
* atomically all at once or in several stages. The operation requests
* a credit for a number of buffer modications in advance, but can
* extend its credit if it needs more.
*
* journal_extend tries to give the running handle more buffer credits.
* It does not guarantee that allocation: this is a best-effort only.
* The calling process MUST be able to deal cleanly with a failure to
* extend here.
*
* Return 0 on success, non-zero on failure.
*
* return code < 0 implies an error
* return code > 0 implies normal transaction-full status.
*/
int journal_extend (handle_t *handle, int nblocks)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
int result;
int wanted;
lock_journal (journal);
result = -EIO;
if (is_handle_aborted(handle))
goto error_out;
result = 1;
/* Don't extend a locked-down transaction! */
if (handle->h_transaction->t_state != T_RUNNING) {
jbd_debug(3, "denied handle %p %d blocks: "
"transaction not running\n", handle, nblocks);
goto error_out;
}
wanted = transaction->t_outstanding_credits + nblocks;
if (wanted > journal->j_max_transaction_buffers) {
jbd_debug(3, "denied handle %p %d blocks: "
"transaction too large\n", handle, nblocks);
goto error_out;
}
if (wanted > log_space_left(journal)) {
jbd_debug(3, "denied handle %p %d blocks: "
"insufficient log space\n", handle, nblocks);
goto error_out;
}
handle->h_buffer_credits += nblocks;
transaction->t_outstanding_credits += nblocks;
result = 0;
jbd_debug(3, "extended handle %p by %d\n", handle, nblocks);
error_out:
unlock_journal (journal);
return result;
}
/*
* journal_restart: restart a handle for a multi-transaction filesystem
* operation.
*
* If the journal_extend() call above fails to grant new buffer credits
* to a running handle, a call to journal_restart will commit the
* handle's transaction so far and reattach the handle to a new
* transaction capabable of guaranteeing the requested number of
* credits.
*/
int journal_restart(handle_t *handle, int nblocks)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
int ret;
/* If we've had an abort of any type, don't even think about
* actually doing the restart! */
if (is_handle_aborted(handle))
return 0;
/* First unlink the handle from its current transaction, and
* start the commit on that. */
J_ASSERT (transaction->t_updates > 0);
J_ASSERT (journal_current_handle() == handle);
transaction->t_outstanding_credits -= handle->h_buffer_credits;
transaction->t_updates--;
if (!transaction->t_updates)
wake_up(&journal->j_wait_updates);
jbd_debug(2, "restarting handle %p\n", handle);
log_start_commit(journal, transaction);
handle->h_buffer_credits = nblocks;
ret = start_this_handle(journal, handle);
return ret;
}
/*
* Barrier operation: establish a transaction barrier.
*
* This locks out any further updates from being started, and blocks
* until all existing updates have completed, returning only once the
* journal is in a quiescent state with no updates running.
*
* The journal lock should not be held on entry.
*/
void journal_lock_updates (journal_t *journal)
{
lock_journal(journal);
++journal->j_barrier_count;
/* Wait until there are no running updates */
while (1) {
transaction_t *transaction = journal->j_running_transaction;
if (!transaction)
break;
if (!transaction->t_updates)
break;
unlock_journal(journal);
sleep_on(&journal->j_wait_updates);
lock_journal(journal);
}
unlock_journal(journal);
/* We have now established a barrier against other normal
* updates, but we also need to barrier against other
* journal_lock_updates() calls to make sure that we serialise
* special journal-locked operations too. */
down(&journal->j_barrier);
}
/*
* Release a transaction barrier obtained with journal_lock_updates().
*
* Should be called without the journal lock held.
*/
void journal_unlock_updates (journal_t *journal)
{
lock_journal(journal);
J_ASSERT (journal->j_barrier_count != 0);
up(&journal->j_barrier);
--journal->j_barrier_count;
wake_up(&journal->j_wait_transaction_locked);
unlock_journal(journal);
}
/*
* journal_get_write_access: notify intent to modify a buffer for metadata
* (not data) update.
*
* If the buffer is already part of the current transaction, then there
* is nothing we need to do. If it is already part of a prior
* transaction which we are still committing to disk, then we need to
* make sure that we do not overwrite the old copy: we do copy-out to
* preserve the copy going to disk. We also account the buffer against
* the handle's metadata buffer credits (unless the buffer is already
* part of the transaction, that is).
*
* Returns an error code or 0 on success.
*
* In full data journalling mode the buffer may be of type BJ_AsyncData,
* because we're write()ing a buffer which is also part of a shared mapping.
*/
static int
do_get_write_access(handle_t *handle, struct journal_head *jh, int force_copy)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
int error;
char *frozen_buffer = NULL;
int need_copy = 0;
jbd_debug(5, "buffer_head %p, force_copy %d\n", jh, force_copy);
JBUFFER_TRACE(jh, "entry");
repeat:
/* @@@ Need to check for errors here at some point. */
/*
* AKPM: neither bdflush nor kupdate run with the BKL. There's
* nothing we can do to prevent them from starting writeout of a
* BUF_DIRTY buffer at any time. And checkpointing buffers are on
* BUF_DIRTY. So. We no longer assert that the buffer is unlocked.
*
* However. It is very wrong for us to allow ext3 to start directly
* altering the ->b_data of buffers which may at that very time be
* undergoing writeout to the client filesystem. This can leave
* the filesystem in an inconsistent, transient state if we crash.
* So what we do is to steal the buffer if it is in checkpoint
* mode and dirty. The journal lock will keep out checkpoint-mode
* state transitions within journal_remove_checkpoint() and the buffer
* is locked to keep bdflush/kupdate/whoever away from it as well.
*
* AKPM: we have replaced all the lock_journal_bh_wait() stuff with a
* simple lock_journal(). This code here will care for locked buffers.
*/
/*
* The buffer_locked() || buffer_dirty() tests here are simply an
* optimisation tweak. If anyone else in the system decides to
* lock this buffer later on, we'll blow up. There doesn't seem
* to be a good reason why they should do this.
*/
if (jh->b_cp_transaction &&
(buffer_locked(jh2bh(jh)) || buffer_dirty(jh2bh(jh)))) {
unlock_journal(journal);
lock_buffer(jh2bh(jh));
spin_lock(&journal_datalist_lock);
if (jh->b_cp_transaction && buffer_dirty(jh2bh(jh))) {
/* OK, we need to steal it */
JBUFFER_TRACE(jh, "stealing from checkpoint mode");
J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
J_ASSERT_JH(jh, jh->b_frozen_data == NULL);
J_ASSERT(handle->h_buffer_credits > 0);
handle->h_buffer_credits--;
/* This will clear BH_Dirty and set BH_JBDDirty. */
JBUFFER_TRACE(jh, "file as BJ_Reserved");
__journal_file_buffer(jh, transaction, BJ_Reserved);
/* And pull it off BUF_DIRTY, onto BUF_CLEAN */
refile_buffer(jh2bh(jh));
/*
* The buffer is now hidden from bdflush. It is
* metadata against the current transaction.
*/
JBUFFER_TRACE(jh, "steal from cp mode is complete");
}
spin_unlock(&journal_datalist_lock);
unlock_buffer(jh2bh(jh));
lock_journal(journal);
goto repeat;
}
J_ASSERT_JH(jh, !buffer_locked(jh2bh(jh)));
error = -EROFS;
if (is_handle_aborted(handle))
goto out_unlocked;
error = 0;
spin_lock(&journal_datalist_lock);
/* The buffer is already part of this transaction if
* b_transaction or b_next_transaction points to it. */
if (jh->b_transaction == transaction ||
jh->b_next_transaction == transaction)
goto done_locked;
/* If there is already a copy-out version of this buffer, then
* we don't need to make another one. */
if (jh->b_frozen_data) {
JBUFFER_TRACE(jh, "has frozen data");
J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
jh->b_next_transaction = transaction;
J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
handle->h_buffer_credits--;
goto done_locked;
}
/* Is there data here we need to preserve? */
if (jh->b_transaction && jh->b_transaction != transaction) {
JBUFFER_TRACE(jh, "owned by older transaction");
J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
J_ASSERT_JH(jh, jh->b_transaction ==
journal->j_committing_transaction);
/* There is one case we have to be very careful about.
* If the committing transaction is currently writing
* this buffer out to disk and has NOT made a copy-out,
* then we cannot modify the buffer contents at all
* right now. The essence of copy-out is that it is the
* extra copy, not the primary copy, which gets
* journaled. If the primary copy is already going to
* disk then we cannot do copy-out here. */
if (jh->b_jlist == BJ_Shadow) {
JBUFFER_TRACE(jh, "on shadow: sleep");
spin_unlock(&journal_datalist_lock);
unlock_journal(journal);
/* commit wakes up all shadow buffers after IO */
sleep_on(&jh2bh(jh)->b_wait);
lock_journal(journal);
goto repeat;
}
/* Only do the copy if the currently-owning transaction
* still needs it. If it is on the Forget list, the
* committing transaction is past that stage. The
* buffer had better remain locked during the kmalloc,
* but that should be true --- we hold the journal lock
* still and the buffer is already on the BUF_JOURNAL
* list so won't be flushed.
*
* Subtle point, though: if this is a get_undo_access,
* then we will be relying on the frozen_data to contain
* the new value of the committed_data record after the
* transaction, so we HAVE to force the frozen_data copy
* in that case. */
if (jh->b_jlist != BJ_Forget || force_copy) {
JBUFFER_TRACE(jh, "generate frozen data");
if (!frozen_buffer) {
JBUFFER_TRACE(jh, "allocate memory for buffer");
spin_unlock(&journal_datalist_lock);
unlock_journal(journal);
frozen_buffer = jbd_kmalloc(jh2bh(jh)->b_size,
GFP_NOFS);
lock_journal(journal);
if (!frozen_buffer) {
printk(KERN_EMERG __FUNCTION__
"OOM for frozen_buffer\n");
JBUFFER_TRACE(jh, "oom!");
error = -ENOMEM;
spin_lock(&journal_datalist_lock);
goto done_locked;
}
goto repeat;
}
jh->b_frozen_data = frozen_buffer;
frozen_buffer = NULL;
need_copy = 1;
}
jh->b_next_transaction = transaction;
}
J_ASSERT(handle->h_buffer_credits > 0);
handle->h_buffer_credits--;
/* Finally, if the buffer is not journaled right now, we need to
* make sure it doesn't get written to disk before the caller
* actually commits the new data. */
if (!jh->b_transaction) {
JBUFFER_TRACE(jh, "no transaction");
J_ASSERT_JH(jh, !jh->b_next_transaction);
jh->b_transaction = transaction;
JBUFFER_TRACE(jh, "file as BJ_Reserved");
__journal_file_buffer(jh, transaction, BJ_Reserved);
}
done_locked:
spin_unlock(&journal_datalist_lock);
if (need_copy) {
struct page *page;
int offset;
char *source;
J_ASSERT_JH(jh, buffer_uptodate(jh2bh(jh)));
page = jh2bh(jh)->b_page;
offset = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK;
source = kmap(page);
memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size);
kunmap(page);
}
/* If we are about to journal a buffer, then any revoke pending
on it is no longer valid. */
journal_cancel_revoke(handle, jh);
out_unlocked:
if (frozen_buffer)
kfree(frozen_buffer);
JBUFFER_TRACE(jh, "exit");
return error;
}
int journal_get_write_access (handle_t *handle, struct buffer_head *bh)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
struct journal_head *jh = journal_add_journal_head(bh);
int rc;
/* We do not want to get caught playing with fields which the
* log thread also manipulates. Make sure that the buffer
* completes any outstanding IO before proceeding. */
lock_journal(journal);
rc = do_get_write_access(handle, jh, 0);
journal_unlock_journal_head(jh);
unlock_journal(journal);
return rc;
}
/*
* When the user wants to journal a newly created buffer_head
* (ie. getblk() returned a new buffer and we are going to populate it
* manually rather than reading off disk), then we need to keep the
* buffer_head locked until it has been completely filled with new
* data. In this case, we should be able to make the assertion that
* the bh is not already part of an existing transaction.
*
* The buffer should already be locked by the caller by this point.
* There is no lock ranking violation: it was a newly created,
* unlocked buffer beforehand. */
int journal_get_create_access (handle_t *handle, struct buffer_head *bh)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
struct journal_head *jh = journal_add_journal_head(bh);
int err;
jbd_debug(5, "journal_head %p\n", jh);
lock_journal(journal);
err = -EROFS;
if (is_handle_aborted(handle))
goto out;
err = 0;
JBUFFER_TRACE(jh, "entry");
/* The buffer may already belong to this transaction due to
* pre-zeroing in the filesystem's new_block code. It may also
* be on the previous, committing transaction's lists, but it
* HAS to be in Forget state in that case: the transaction must
* have deleted the buffer for it to be reused here. */
J_ASSERT_JH(jh, (jh->b_transaction == transaction ||
jh->b_transaction == NULL ||
(jh->b_transaction == journal->j_committing_transaction &&
jh->b_jlist == BJ_Forget)));
J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
J_ASSERT_JH(jh, buffer_locked(jh2bh(jh)));
J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
handle->h_buffer_credits--;
spin_lock(&journal_datalist_lock);
if (jh->b_transaction == NULL) {
jh->b_transaction = transaction;
JBUFFER_TRACE(jh, "file as BJ_Reserved");
__journal_file_buffer(jh, transaction, BJ_Reserved);
JBUFFER_TRACE(jh, "refile");
refile_buffer(jh2bh(jh));
} else if (jh->b_transaction == journal->j_committing_transaction) {
JBUFFER_TRACE(jh, "set next transaction");
jh->b_next_transaction = transaction;
}
spin_unlock(&journal_datalist_lock);
/*
* akpm: I added this. ext3_alloc_branch can pick up new indirect
* blocks which contain freed but then revoked metadata. We need
* to cancel the revoke in case we end up freeing it yet again
* and the reallocating as data - this would cause a second revoke,
* which hits an assertion error.
*/
JBUFFER_TRACE(jh, "cancelling revoke");
journal_cancel_revoke(handle, jh);
journal_unlock_journal_head(jh);
out:
unlock_journal(journal);
return err;
}
/*
* journal_get_undo_access: Notify intent to modify metadata with non-
* rewindable consequences
*
* Sometimes there is a need to distinguish between metadata which has
* been committed to disk and that which has not. The ext3fs code uses
* this for freeing and allocating space: we have to make sure that we
* do not reuse freed space until the deallocation has been committed,
* since if we overwrote that space we would make the delete
* un-rewindable in case of a crash.
*
* To deal with that, journal_get_undo_access requests write access to a
* buffer for parts of non-rewindable operations such as delete
* operations on the bitmaps. The journaling code must keep a copy of
* the buffer's contents prior to the undo_access call until such time
* as we know that the buffer has definitely been committed to disk.
*
* We never need to know which transaction the committed data is part
* of: buffers touched here are guaranteed to be dirtied later and so
* will be committed to a new transaction in due course, at which point
* we can discard the old committed data pointer.
*
* Returns error number or 0 on success.
*/
int journal_get_undo_access (handle_t *handle, struct buffer_head *bh)
{
journal_t *journal = handle->h_transaction->t_journal;
int err;
struct journal_head *jh = journal_add_journal_head(bh);
JBUFFER_TRACE(jh, "entry");
lock_journal(journal);
/* Do this first --- it can drop the journal lock, so we want to
* make sure that obtaining the committed_data is done
* atomically wrt. completion of any outstanding commits. */
err = do_get_write_access (handle, jh, 1);
if (err)
goto out;
if (!jh->b_committed_data) {
/* Copy out the current buffer contents into the
* preserved, committed copy. */
JBUFFER_TRACE(jh, "generate b_committed data");
jh->b_committed_data = jbd_kmalloc(jh2bh(jh)->b_size,
GFP_NOFS);
if (!jh->b_committed_data) {
printk(KERN_EMERG __FUNCTION__
": No memory for committed data!\n");
err = -ENOMEM;
goto out;
}
memcpy (jh->b_committed_data, jh2bh(jh)->b_data,
jh2bh(jh)->b_size);
}
out:
if (!err)
J_ASSERT_JH(jh, jh->b_committed_data);
journal_unlock_journal_head(jh);
unlock_journal(journal);
return err;
}
/*
* journal_dirty_data: mark a buffer as containing dirty data which
* needs to be flushed before we can commit the current transaction.
*
* The buffer is placed on the transaction's data list and is marked as
* belonging to the transaction.
*
* If `async' is set then the writebask will be initiated by the caller
* using submit_bh -> end_buffer_io_async. We put the buffer onto
* t_async_datalist.
*
* Returns error number or 0 on success.
*
* journal_dirty_data() can be called via page_launder->ext3_writepage
* by kswapd. So it cannot block. Happily, there's nothing here
* which needs lock_journal if `async' is set.
*
* When the buffer is on the current transaction we freely move it
* between BJ_AsyncData and BJ_SyncData according to who tried to
* change its state last.
*/
int journal_dirty_data (handle_t *handle, struct buffer_head *bh, int async)
{
journal_t *journal = handle->h_transaction->t_journal;
int need_brelse = 0;
int wanted_jlist = async ? BJ_AsyncData : BJ_SyncData;
struct journal_head *jh;
if (is_handle_aborted(handle))
return 0;
jh = journal_add_journal_head(bh);
JBUFFER_TRACE(jh, "entry");
/*
* The buffer could *already* be dirty. Writeout can start
* at any time.
*/
jbd_debug(4, "jh: %p, tid:%d\n", jh, handle->h_transaction->t_tid);
/*
* What if the buffer is already part of a running transaction?
*
* There are two cases:
* 1) It is part of the current running transaction. Refile it,
* just in case we have allocated it as metadata, deallocated
* it, then reallocated it as data.
* 2) It is part of the previous, still-committing transaction.
* If all we want to do is to guarantee that the buffer will be
* written to disk before this new transaction commits, then
* being sure that the *previous* transaction has this same
* property is sufficient for us! Just leave it on its old
* transaction.
*
* In case (2), the buffer must not already exist as metadata
* --- that would violate write ordering (a transaction is free
* to write its data at any point, even before the previous
* committing transaction has committed). The caller must
* never, ever allow this to happen: there's nothing we can do
* about it in this layer.
*/
spin_lock(&journal_datalist_lock);
if (jh->b_transaction) {
JBUFFER_TRACE(jh, "has transaction");
if (jh->b_transaction != handle->h_transaction) {
JBUFFER_TRACE(jh, "belongs to older transaction");
J_ASSERT_JH(jh, jh->b_transaction ==
journal->j_committing_transaction);
/* @@@ IS THIS TRUE ? */
/*
* Not any more. Scenario: someone does a write()
* in data=journal mode. The buffer's transaction has
* moved into commit. Then someone does another
* write() to the file. We do the frozen data copyout
* and set b_next_transaction to point to j_running_t.
* And while we're in that state, someone does a
* writepage() in an attempt to pageout the same area
* of the file via a shared mapping. At present that
* calls journal_dirty_data(), and we get right here.
* It may be too late to journal the data. Simply
* falling through to the next test will suffice: the
* data will be dirty and wil be checkpointed. The
* ordering comments in the next comment block still
* apply.
*/
//J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
/*
* If we're journalling data, and this buffer was
* subject to a write(), it could be metadata, forget
* or shadow against the committing transaction. Now,
* someone has dirtied the same darn page via a mapping
* and it is being writepage()'d.
* We *could* just steal the page from commit, with some
* fancy locking there. Instead, we just skip it -
* don't tie the page's buffers to the new transaction
* at all.
* Implication: if we crash before the writepage() data
* is written into the filesystem, recovery will replay
* the write() data.
*/
if (jh->b_jlist != BJ_None &&
jh->b_jlist != BJ_SyncData &&
jh->b_jlist != BJ_AsyncData) {
JBUFFER_TRACE(jh, "Not stealing");
goto no_journal;
}
/*
* This buffer may be undergoing writeout in commit. We
* can't return from here and let the caller dirty it
* again because that can cause the write-out loop in
* commit to never terminate.
*/
if (!async && buffer_dirty(bh)) {
atomic_inc(&bh->b_count);
spin_unlock(&journal_datalist_lock);
need_brelse = 1;
ll_rw_block(WRITE, 1, &bh);
wait_on_buffer(bh);
spin_lock(&journal_datalist_lock);
/* The buffer may become locked again at any
time if it is redirtied */
}
/* journal_clean_data_list() may have got there first */
if (jh->b_transaction != NULL) {
JBUFFER_TRACE(jh, "unfile from commit");
__journal_unfile_buffer(jh);
jh->b_transaction = NULL;
}
/* The buffer will be refiled below */
}
/*
* Special case --- the buffer might actually have been
* allocated and then immediately deallocated in the previous,
* committing transaction, so might still be left on that
* transaction's metadata lists.
*/
if (jh->b_jlist != wanted_jlist) {
JBUFFER_TRACE(jh, "not on correct data list: unfile");
J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow);
__journal_unfile_buffer(jh);
jh->b_transaction = NULL;
JBUFFER_TRACE(jh, "file as data");
__journal_file_buffer(jh, handle->h_transaction,
wanted_jlist);
}
} else {
JBUFFER_TRACE(jh, "not on a transaction");
__journal_file_buffer(jh, handle->h_transaction, wanted_jlist);
}
no_journal:
spin_unlock(&journal_datalist_lock);
if (need_brelse) {
BUFFER_TRACE(bh, "brelse");
__brelse(bh);
}
JBUFFER_TRACE(jh, "exit");
journal_unlock_journal_head(jh);
return 0;
}
/*
* journal_dirty_metadata: mark a buffer as containing dirty metadata
* which needs to be journaled as part of the current transaction.
*
* The buffer is placed on the transaction's metadata list and is marked
* as belonging to the transaction.
*
* Special care needs to be taken if the buffer already belongs to the
* current committing transaction (in which case we should have frozen
* data present for that commit). In that case, we don't relink the
* buffer: that only gets done when the old transaction finally
* completes its commit.
*
* Returns error number or 0 on success.
*/
int journal_dirty_metadata (handle_t *handle, struct buffer_head *bh)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
struct journal_head *jh = bh2jh(bh);
jbd_debug(5, "journal_head %p\n", jh);
JBUFFER_TRACE(jh, "entry");
lock_journal(journal);
if (is_handle_aborted(handle))
goto out_unlock;
spin_lock(&journal_datalist_lock);
set_bit(BH_JBDDirty, &bh->b_state);
set_buffer_flushtime(bh);
J_ASSERT_JH(jh, jh->b_transaction != NULL);
/*
* Metadata already on the current transaction list doesn't
* need to be filed. Metadata on another transaction's list must
* be committing, and will be refiled once the commit completes:
* leave it alone for now.
*/
if (jh->b_transaction != transaction) {
JBUFFER_TRACE(jh, "already on other transaction");
J_ASSERT_JH(jh, jh->b_transaction ==
journal->j_committing_transaction);
J_ASSERT_JH(jh, jh->b_next_transaction == transaction);
/* And this case is illegal: we can't reuse another
* transaction's data buffer, ever. */
/* FIXME: writepage() should be journalled */
J_ASSERT_JH(jh, jh->b_jlist != BJ_SyncData);
goto done_locked;
}
/* That test should have eliminated the following case: */
J_ASSERT_JH(jh, jh->b_frozen_data == 0);
JBUFFER_TRACE(jh, "file as BJ_Metadata");
__journal_file_buffer(jh, handle->h_transaction, BJ_Metadata);
done_locked:
spin_unlock(&journal_datalist_lock);
JBUFFER_TRACE(jh, "exit");
out_unlock:
unlock_journal(journal);
return 0;
}
#if 0
/*
* journal_release_buffer: undo a get_write_access without any buffer
* updates, if the update decided in the end that it didn't need access.
*
* journal_get_write_access() can block, so it is quite possible for a
* journaling component to decide after the write access is returned
* that global state has changed and the update is no longer required. */
void journal_release_buffer (handle_t *handle, struct buffer_head *bh)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
struct journal_head *jh = bh2jh(bh);
lock_journal(journal);
JBUFFER_TRACE(jh, "entry");
/* If the buffer is reserved but not modified by this
* transaction, then it is safe to release it. In all other
* cases, just leave the buffer as it is. */
spin_lock(&journal_datalist_lock);
if (jh->b_jlist == BJ_Reserved && jh->b_transaction == transaction &&
!buffer_jdirty(jh2bh(jh))) {
JBUFFER_TRACE(jh, "unused: refiling it");
handle->h_buffer_credits++;
__journal_refile_buffer(jh);
}
spin_unlock(&journal_datalist_lock);
JBUFFER_TRACE(jh, "exit");
unlock_journal(journal);
}
#endif
/*
* journal_forget: bforget() for potentially-journaled buffers. We can
* only do the bforget if there are no commits pending against the
* buffer. If the buffer is dirty in the current running transaction we
* can safely unlink it.
*
* bh may not be a journalled buffer at all - it may be a non-JBD
* buffer which came off the hashtable. Check for this.
*
* Decrements bh->b_count by one.
*
* Allow this call even if the handle has aborted --- it may be part of
* the caller's cleanup after an abort.
*/
void journal_forget (handle_t *handle, struct buffer_head *bh)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
struct journal_head *jh;
BUFFER_TRACE(bh, "entry");
lock_journal(journal);
spin_lock(&journal_datalist_lock);
if (!buffer_jbd(bh))
goto not_jbd;
jh = bh2jh(bh);
if (jh->b_transaction == handle->h_transaction) {
J_ASSERT_JH(jh, !jh->b_frozen_data);
/* If we are forgetting a buffer which is already part
* of this transaction, then we can just drop it from
* the transaction immediately. */
clear_bit(BH_Dirty, &bh->b_state);
clear_bit(BH_JBDDirty, &bh->b_state);
JBUFFER_TRACE(jh, "belongs to current transaction: unfile");
J_ASSERT_JH(jh, !jh->b_committed_data);
__journal_unfile_buffer(jh);
jh->b_transaction = 0;
/*
* We are no longer going to journal this buffer.
* However, the commit of this transaction is still
* important to the buffer: the delete that we are now
* processing might obsolete an old log entry, so by
* committing, we can satisfy the buffer's checkpoint.
*
* So, if we have a checkpoint on the buffer, we should
* now refile the buffer on our BJ_Forget list so that
* we know to remove the checkpoint after we commit.
*/
if (jh->b_cp_transaction) {
__journal_file_buffer(jh, transaction, BJ_Forget);
} else {
__journal_remove_journal_head(bh);
__brelse(bh);
if (!buffer_jbd(bh)) {
spin_unlock(&journal_datalist_lock);
unlock_journal(journal);
__bforget(bh);
return;
}
}
} else if (jh->b_transaction) {
J_ASSERT_JH(jh, (jh->b_transaction ==
journal->j_committing_transaction));
/* However, if the buffer is still owned by a prior
* (committing) transaction, we can't drop it yet... */
JBUFFER_TRACE(jh, "belongs to older transaction");
/* ... but we CAN drop it from the new transaction if we
* have also modified it since the original commit. */
if (jh->b_next_transaction) {
J_ASSERT(jh->b_next_transaction == transaction);
jh->b_next_transaction = NULL;
}
}
not_jbd:
spin_unlock(&journal_datalist_lock);
unlock_journal(journal);
__brelse(bh);
return;
}
#if 0 /* Unused */
/*
* journal_sync_buffer: flush a potentially-journaled buffer to disk.
*
* Used for O_SYNC filesystem operations. If the buffer is journaled,
* we need to complete the O_SYNC by waiting for the transaction to
* complete. It is an error to call journal_sync_buffer before
* journal_stop!
*/
void journal_sync_buffer(struct buffer_head *bh)
{
transaction_t *transaction;
journal_t *journal;
long sequence;
struct journal_head *jh;
/* If the buffer isn't journaled, this is easy: just sync it to
* disk. */
BUFFER_TRACE(bh, "entry");
spin_lock(&journal_datalist_lock);
if (!buffer_jbd(bh)) {
spin_unlock(&journal_datalist_lock);
return;
}
jh = bh2jh(bh);
if (jh->b_transaction == NULL) {
/* If the buffer has already been journaled, then this
* is a noop. */
if (jh->b_cp_transaction == NULL) {
spin_unlock(&journal_datalist_lock);
return;
}
atomic_inc(&bh->b_count);
spin_unlock(&journal_datalist_lock);
ll_rw_block (WRITE, 1, &bh);
wait_on_buffer(bh);
__brelse(bh);
goto out;
}
/* Otherwise, just wait until the transaction is synced to disk. */
transaction = jh->b_transaction;
journal = transaction->t_journal;
sequence = transaction->t_tid;
spin_unlock(&journal_datalist_lock);
jbd_debug(2, "requesting commit for jh %p\n", jh);
log_start_commit (journal, transaction);
while (tid_gt(sequence, journal->j_commit_sequence)) {
wake_up(&journal->j_wait_done_commit);
sleep_on(&journal->j_wait_done_commit);
}
JBUFFER_TRACE(jh, "exit");
out:
return;
}
#endif
/*
* All done for a particular handle.
*
* There is not much action needed here. We just return any remaining
* buffer credits to the transaction and remove the handle. The only
* complication is that we need to start a commit operation if the
* filesystem is marked for synchronous update.
*
* journal_stop itself will not usually return an error, but it may
* do so in unusual circumstances. In particular, expect it to
* return -EIO if a journal_abort has been executed since the
* transaction began.
*/
int journal_stop(handle_t *handle)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
int old_handle_count, err;
if (!handle)
return 0;
J_ASSERT (transaction->t_updates > 0);
J_ASSERT (journal_current_handle() == handle);
if (is_handle_aborted(handle))
err = -EIO;
else
err = 0;
if (--handle->h_ref > 0) {
jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,
handle->h_ref);
return err;
}
jbd_debug(4, "Handle %p going down\n", handle);
/*
* Implement synchronous transaction batching. If the handle
* was synchronous, don't force a commit immediately. Let's
* yield and let another thread piggyback onto this transaction.
* Keep doing that while new threads continue to arrive.
* It doesn't cost much - we're about to run a commit and sleep
* on IO anyway. Speeds up many-threaded, many-dir operations
* by 30x or more...
*/
if (handle->h_sync) {
do {
old_handle_count = transaction->t_handle_count;
set_current_state(TASK_RUNNING);
current->policy |= SCHED_YIELD;
schedule();
} while (old_handle_count != transaction->t_handle_count);
}
current->journal_info = NULL;
transaction->t_outstanding_credits -= handle->h_buffer_credits;
transaction->t_updates--;
if (!transaction->t_updates) {
wake_up(&journal->j_wait_updates);
if (journal->j_barrier_count)
wake_up(&journal->j_wait_transaction_locked);
}
/*
* If the handle is marked SYNC, we need to set another commit
* going! We also want to force a commit if the current
* transaction is occupying too much of the log, or if the
* transaction is too old now.
*/
if (handle->h_sync ||
transaction->t_outstanding_credits >
journal->j_max_transaction_buffers ||
time_after_eq(jiffies, transaction->t_expires)) {
/* Do this even for aborted journals: an abort still
* completes the commit thread, it just doesn't write
* anything to disk. */
tid_t tid = transaction->t_tid;
jbd_debug(2, "transaction too old, requesting commit for "
"handle %p\n", handle);
/* This is non-blocking */
log_start_commit(journal, transaction);
/*
* Special case: JFS_SYNC synchronous updates require us
* to wait for the commit to complete.
*/
if (handle->h_sync && !(current->flags & PF_MEMALLOC))
log_wait_commit(journal, tid);
}
kfree(handle);
return err;
}
/*
* For synchronous operations: force any uncommitted trasnactions
* to disk. May seem kludgy, but it reuses all the handle batching
* code in a very simple manner.
*/
int journal_force_commit(journal_t *journal)
{
handle_t *handle;
int ret = 0;
lock_kernel();
handle = journal_start(journal, 1);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
goto out;
}
handle->h_sync = 1;
journal_stop(handle);
out:
unlock_kernel();
return ret;
}
/*
*
* List management code snippets: various functions for manipulating the
* transaction buffer lists.
*
*/
/*
* Append a buffer to a transaction list, given the transaction's list head
* pointer.
* journal_datalist_lock is held.
*/
static inline void
__blist_add_buffer(struct journal_head **list, struct journal_head *jh)
{
if (!*list) {
jh->b_tnext = jh->b_tprev = jh;
*list = jh;
} else {
/* Insert at the tail of the list to preserve order */
struct journal_head *first = *list, *last = first->b_tprev;
jh->b_tprev = last;
jh->b_tnext = first;
last->b_tnext = first->b_tprev = jh;
}
}
/*
* Remove a buffer from a transaction list, given the transaction's list
* head pointer.
*
* Called with journal_datalist_lock held, and the journal may not
* be locked.
*/
static inline void
__blist_del_buffer(struct journal_head **list, struct journal_head *jh)
{
if (*list == jh) {
*list = jh->b_tnext;
if (*list == jh)
*list = 0;
}
jh->b_tprev->b_tnext = jh->b_tnext;
jh->b_tnext->b_tprev = jh->b_tprev;
}
/*
* Remove a buffer from the appropriate transaction list.
*
* Note that this function can *change* the value of
* bh->b_transaction->t_sync_datalist, t_async_datalist, t_buffers, t_forget,
* t_iobuf_list, t_shadow_list, t_log_list or t_reserved_list. If the caller
* is holding onto a copy of one of thee pointers, it could go bad.
* Generally the caller needs to re-read the pointer from the transaction_t.
*
* If bh->b_jlist is BJ_SyncData or BJ_AsyncData then we may have been called
* via journal_try_to_free_buffer() or journal_clean_data_list(). In that
* case, journal_datalist_lock will be held, and the journal may not be locked.
*/
void __journal_unfile_buffer(struct journal_head *jh)
{
struct journal_head **list = 0;
transaction_t * transaction;
assert_spin_locked(&journal_datalist_lock);
transaction = jh->b_transaction;
#ifdef __SMP__
J_ASSERT (current->lock_depth >= 0);
#endif
J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
if (jh->b_jlist != BJ_None)
J_ASSERT_JH(jh, transaction != 0);
switch (jh->b_jlist) {
case BJ_None:
return;
case BJ_SyncData:
list = &transaction->t_sync_datalist;
break;
case BJ_AsyncData:
list = &transaction->t_async_datalist;
break;
case BJ_Metadata:
transaction->t_nr_buffers--;
J_ASSERT_JH(jh, transaction->t_nr_buffers >= 0);
list = &transaction->t_buffers;
break;
case BJ_Forget:
list = &transaction->t_forget;
break;
case BJ_IO:
list = &transaction->t_iobuf_list;
break;
case BJ_Shadow:
list = &transaction->t_shadow_list;
break;
case BJ_LogCtl:
list = &transaction->t_log_list;
break;
case BJ_Reserved:
list = &transaction->t_reserved_list;
break;
}
__blist_del_buffer(list, jh);
jh->b_jlist = BJ_None;
if (test_and_clear_bit(BH_JBDDirty, &jh2bh(jh)->b_state)) {
set_bit(BH_Dirty, &jh2bh(jh)->b_state);
}
}
void journal_unfile_buffer(struct journal_head *jh)
{
spin_lock(&journal_datalist_lock);
__journal_unfile_buffer(jh);
spin_unlock(&journal_datalist_lock);
}
/*
* Called from journal_try_to_free_buffers(). The journal is not
* locked. lru_list_lock is not held.
*
* Here we see why journal_datalist_lock is global and not per-journal.
* We cannot get back to this buffer's journal pointer without locking
* out journal_clean_data_list() in some manner.
*
* One could use journal_datalist_lock to get unracy access to a
* per-journal lock.
*
* Called with journal_datalist_lock held.
*
* Returns non-zero iff we were able to free the journal_head.
*/
static int __journal_try_to_free_buffer(struct buffer_head *bh,
int *locked_or_dirty)
{
struct journal_head *jh;
assert_spin_locked(&journal_datalist_lock);
jh = bh2jh(bh);
if (buffer_locked(bh) || buffer_dirty(bh)) {
*locked_or_dirty = 1;
goto out;
}
if (!buffer_uptodate(bh))
goto out;
if (jh->b_next_transaction != 0)
goto out;
if (jh->b_transaction != 0 && jh->b_cp_transaction == 0) {
if (jh->b_jlist == BJ_SyncData || jh->b_jlist==BJ_AsyncData) {
/* A written-back ordered data buffer */
JBUFFER_TRACE(jh, "release data");
__journal_unfile_buffer(jh);
jh->b_transaction = 0;
__journal_remove_journal_head(bh);
__brelse(bh);
}
}
else if (jh->b_cp_transaction != 0 && jh->b_transaction == 0) {
/* written-back checkpointed metadata buffer */
if (jh->b_jlist == BJ_None) {
JBUFFER_TRACE(jh, "remove from checkpoint list");
__journal_remove_checkpoint(jh);
__journal_remove_journal_head(bh);
__brelse(bh);
}
}
return !buffer_jbd(bh);
out:
return 0;
}
/*
* journal_try_to_free_buffers(). For all the buffers on this page,
* if they are fully written out ordered data, move them onto BUF_CLEAN
* so try_to_free_buffers() can reap them. Called with lru_list_lock
* not held. Does its own locking.
*
* This complicates JBD locking somewhat. We aren't protected by the
* BKL here. We wish to remove the buffer from its committing or
* running transaction's ->t_datalist via __journal_unfile_buffer.
*
* This may *change* the value of transaction_t->t_datalist, so anyone
* who looks at t_datalist needs to lock against this function.
*
* Even worse, someone may be doing a journal_dirty_data on this
* buffer. So we need to lock against that. journal_dirty_data()
* will come out of the lock with the buffer dirty, which makes it
* ineligible for release here.
*
* Who else is affected by this? hmm... Really the only contender
* is do_get_write_access() - it could be looking at the buffer while
* journal_try_to_free_buffer() is changing its state. But that
* cannot happen because we never reallocate freed data as metadata
* while the data is part of a transaction. Yes?
*
* This function returns non-zero if we wish try_to_free_buffers()
* to be called. We do this is the page is releasable by try_to_free_buffers().
* We also do it if the page has locked or dirty buffers and the caller wants
* us to perform sync or async writeout.
*/
int journal_try_to_free_buffers(journal_t *journal,
struct page *page, int gfp_mask)
{
struct buffer_head *bh;
struct buffer_head *tmp;
int locked_or_dirty = 0;
int call_ttfb = 1;
J_ASSERT(PageLocked(page));
bh = page->buffers;
tmp = bh;
spin_lock(&journal_datalist_lock);
do {
struct buffer_head *p = tmp;
tmp = tmp->b_this_page;
if (buffer_jbd(p))
if (!__journal_try_to_free_buffer(p, &locked_or_dirty))
call_ttfb = 0;
} while (tmp != bh);
spin_unlock(&journal_datalist_lock);
if (!(gfp_mask & (__GFP_IO|__GFP_WAIT)))
goto out;
if (!locked_or_dirty)
goto out;
/*
* The VM wants us to do writeout, or to block on IO, or both.
* So we allow try_to_free_buffers to be called even if the page
* still has journalled buffers.
*/
call_ttfb = 1;
out:
return call_ttfb;
}
/*
* This buffer is no longer needed. If it is on an older transaction's
* checkpoint list we need to record it on this transaction's forget list
* to pin this buffer (and hence its checkpointing transaction) down until
* this transaction commits. If the buffer isn't on a checkpoint list, we
* release it.
* Returns non-zero if JBD no longer has an interest in the buffer.
*/
static int dispose_buffer(struct journal_head *jh,
transaction_t *transaction)
{
int may_free = 1;
struct buffer_head *bh = jh2bh(jh);
spin_lock(&journal_datalist_lock);
__journal_unfile_buffer(jh);
jh->b_transaction = 0;
if (jh->b_cp_transaction) {
JBUFFER_TRACE(jh, "on running+cp transaction");
__journal_file_buffer(jh, transaction, BJ_Forget);
clear_bit(BH_JBDDirty, &bh->b_state);
may_free = 0;
} else {
JBUFFER_TRACE(jh, "on running transaction");
__journal_remove_journal_head(bh);
__brelse(bh);
}
spin_unlock(&journal_datalist_lock);
return may_free;
}
/*
* journal_flushpage
*
* This code is tricky. It has a number of cases to deal with.
*
* There are two invariants which this code relies on:
*
* i_size must be updated on disk before we start calling flushpage on the
* data.
*
* This is done in ext3 by defining an ext3_setattr method which
* updates i_size before truncate gets going. By maintaining this
* invariant, we can be sure that it is safe to throw away any buffers
* attached to the current transaction: once the transaction commits,
* we know that the data will not be needed.
*
* Note however that we can *not* throw away data belonging to the
* previous, committing transaction!
*
* Any disk blocks which *are* part of the previous, committing
* transaction (and which therefore cannot be discarded immediately) are
* not going to be reused in the new running transaction
*
* The bitmap committed_data images guarantee this: any block which is
* allocated in one transaction and removed in the next will be marked
* as in-use in the committed_data bitmap, so cannot be reused until
* the next transaction to delete the block commits. This means that
* leaving committing buffers dirty is quite safe: the disk blocks
* cannot be reallocated to a different file and so buffer aliasing is
* not possible.
*
*
* The above applies mainly to ordered data mode. In writeback mode we
* don't make guarantees about the order in which data hits disk --- in
* particular we don't guarantee that new dirty data is flushed before
* transaction commit --- so it is always safe just to discard data
* immediately in that mode. --sct
*/
/*
* The journal_unmap_buffer helper function returns zero if the buffer
* concerned remains pinned as an anonymous buffer belonging to an older
* transaction.
*
* We're outside-transaction here. Either or both of j_running_transaction
* and j_committing_transaction may be NULL.
*/
static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
{
transaction_t *transaction;
struct journal_head *jh;
int may_free = 1;
BUFFER_TRACE(bh, "entry");
if (!buffer_mapped(bh))
return 1;
/* It is safe to proceed here without the
* journal_datalist_spinlock because the buffers cannot be
* stolen by try_to_free_buffers as long as we are holding the
* page lock. --sct */
if (!buffer_jbd(bh))
goto zap_buffer;
jh = bh2jh(bh);
transaction = jh->b_transaction;
if (transaction == NULL) {
/* First case: not on any transaction. If it
* has no checkpoint link, then we can zap it:
* it's a writeback-mode buffer so we don't care
* if it hits disk safely. */
if (!jh->b_cp_transaction) {
JBUFFER_TRACE(jh, "not on any transaction: zap");
goto zap_buffer;
}
if (!buffer_dirty(bh)) {
/* bdflush has written it. We can drop it now */
goto zap_buffer;
}
/* OK, it must be in the journal but still not
* written fully to disk: it's metadata or
* journaled data... */
if (journal->j_running_transaction) {
/* ... and once the current transaction has
* committed, the buffer won't be needed any
* longer. */
JBUFFER_TRACE(jh, "checkpointed: add to BJ_Forget");
return dispose_buffer(jh,
journal->j_running_transaction);
} else {
/* There is no currently-running transaction. So the
* orphan record which we wrote for this file must have
* passed into commit. We must attach this buffer to
* the committing transaction, if it exists. */
if (journal->j_committing_transaction) {
JBUFFER_TRACE(jh, "give to committing trans");
return dispose_buffer(jh,
journal->j_committing_transaction);
} else {
/* The orphan record's transaction has
* committed. We can cleanse this buffer */
clear_bit(BH_JBDDirty, &bh->b_state);
goto zap_buffer;
}
}
} else if (transaction == journal->j_committing_transaction) {
/* If it is committing, we simply cannot touch it. We
* can remove it's next_transaction pointer from the
* running transaction if that is set, but nothing
* else. */
JBUFFER_TRACE(jh, "on committing transaction");
if (jh->b_next_transaction) {
J_ASSERT(jh->b_next_transaction ==
journal->j_running_transaction);
jh->b_next_transaction = NULL;
}
return 0;
} else {
/* Good, the buffer belongs to the running transaction.
* We are writing our own transaction's data, not any
* previous one's, so it is safe to throw it away
* (remember that we expect the filesystem to have set
* i_size already for this truncate so recovery will not
* expose the disk blocks we are discarding here.) */
J_ASSERT_JH(jh, transaction == journal->j_running_transaction);
may_free = dispose_buffer(jh, transaction);
}
zap_buffer:
if (buffer_dirty(bh))
mark_buffer_clean(bh);
J_ASSERT_BH(bh, !buffer_jdirty(bh));
clear_bit(BH_Uptodate, &bh->b_state);
clear_bit(BH_Mapped, &bh->b_state);
clear_bit(BH_Req, &bh->b_state);
clear_bit(BH_New, &bh->b_state);
return may_free;
}
/*
* Return non-zero if the page's buffers were successfully reaped
*/
int journal_flushpage(journal_t *journal,
struct page *page,
unsigned long offset)
{
struct buffer_head *head, *bh, *next;
unsigned int curr_off = 0;
int may_free = 1;
if (!PageLocked(page))
BUG();
if (!page->buffers)
return 1;
/* We will potentially be playing with lists other than just the
* data lists (especially for journaled data mode), so be
* cautious in our locking. */
lock_journal(journal);
head = bh = page->buffers;
do {
unsigned int next_off = curr_off + bh->b_size;
next = bh->b_this_page;
/* AKPM: doing lock_buffer here may be overly paranoid */
if (offset <= curr_off) {
/* This block is wholly outside the truncation point */
lock_buffer(bh);
may_free &= journal_unmap_buffer(journal, bh);
unlock_buffer(bh);
}
curr_off = next_off;
bh = next;
} while (bh != head);
unlock_journal(journal);
if (!offset) {
if (!may_free || !try_to_free_buffers(page, 0))
return 0;
J_ASSERT(page->buffers == NULL);
}
return 1;
}
/*
* File a buffer on the given transaction list.
*/
void __journal_file_buffer(struct journal_head *jh,
transaction_t *transaction, int jlist)
{
struct journal_head **list = 0;
assert_spin_locked(&journal_datalist_lock);
#ifdef __SMP__
J_ASSERT (current->lock_depth >= 0);
#endif
J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
J_ASSERT_JH(jh, jh->b_transaction == transaction ||
jh->b_transaction == 0);
if (jh->b_transaction) {
if (jh->b_jlist == jlist)
return;
__journal_unfile_buffer(jh);
} else {
jh->b_transaction = transaction;
}
switch (jlist) {
case BJ_None:
J_ASSERT_JH(jh, !jh->b_committed_data);
J_ASSERT_JH(jh, !jh->b_frozen_data);
return;
case BJ_SyncData:
list = &transaction->t_sync_datalist;
break;
case BJ_AsyncData:
list = &transaction->t_async_datalist;
break;
case BJ_Metadata:
transaction->t_nr_buffers++;
list = &transaction->t_buffers;
break;
case BJ_Forget:
list = &transaction->t_forget;
break;
case BJ_IO:
list = &transaction->t_iobuf_list;
break;
case BJ_Shadow:
list = &transaction->t_shadow_list;
break;
case BJ_LogCtl:
list = &transaction->t_log_list;
break;
case BJ_Reserved:
list = &transaction->t_reserved_list;
break;
}
__blist_add_buffer(list, jh);
jh->b_jlist = jlist;
if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
jlist == BJ_Shadow || jlist == BJ_Forget) {
if (atomic_set_buffer_clean(jh2bh(jh))) {
set_bit(BH_JBDDirty, &jh2bh(jh)->b_state);
}
}
}
void journal_file_buffer(struct journal_head *jh,
transaction_t *transaction, int jlist)
{
spin_lock(&journal_datalist_lock);
__journal_file_buffer(jh, transaction, jlist);
spin_unlock(&journal_datalist_lock);
}
/*
* Remove a buffer from its current buffer list in preparation for
* dropping it from its current transaction entirely. If the buffer has
* already started to be used by a subsequent transaction, refile the
* buffer on that transaction's metadata list.
*/
void __journal_refile_buffer(struct journal_head *jh)
{
assert_spin_locked(&journal_datalist_lock);
#ifdef __SMP__
J_ASSERT_JH(jh, current->lock_depth >= 0);
#endif
__journal_unfile_buffer(jh);
/* If the buffer is now unused, just drop it. If it has been
modified by a later transaction, add it to the new
transaction's metadata list. */
jh->b_transaction = jh->b_next_transaction;
jh->b_next_transaction = NULL;
if (jh->b_transaction != NULL) {
__journal_file_buffer(jh, jh->b_transaction, BJ_Metadata);
J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING);
} else {
/* Onto BUF_DIRTY for writeback */
refile_buffer(jh2bh(jh));
}
}
/*
* For the unlocked version of this call, also make sure that any
* hanging journal_head is cleaned up if necessary.
*
* __journal_refile_buffer is usually called as part of a single locked
* operation on a buffer_head, in which the caller is probably going to
* be hooking the journal_head onto other lists. In that case it is up
* to the caller to remove the journal_head if necessary. For the
* unlocked journal_refile_buffer call, the caller isn't going to be
* doing anything else to the buffer so we need to do the cleanup
* ourselves to avoid a jh leak.
*
* *** The journal_head may be freed by this call! ***
*/
void journal_refile_buffer(struct journal_head *jh)
{
struct buffer_head *bh;
spin_lock(&journal_datalist_lock);
bh = jh2bh(jh);
__journal_refile_buffer(jh);
__journal_remove_journal_head(bh);
spin_unlock(&journal_datalist_lock);
__brelse(bh);
}
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