path: root/fs/jbd2/commit.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * linux/fs/jbd2/commit.c
 *
 * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
 *
 * Copyright 1998 Red Hat corp --- All Rights Reserved
 *
 * Journal commit routines for the generic filesystem journaling code;
 * part of the ext2fs journaling system.
 */

#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd2.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/jiffies.h>
#include <linux/crc32.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/bitops.h>
#include <trace/events/jbd2.h>

/*
 * IO end handler for temporary buffer_heads handling writes to the journal.
 */
static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
{
	struct buffer_head *orig_bh = bh->b_private;

	BUFFER_TRACE(bh, "");
	if (uptodate)
		set_buffer_uptodate(bh);
	else
		clear_buffer_uptodate(bh);
	if (orig_bh) {
		clear_bit_unlock(BH_Shadow, &orig_bh->b_state);
		smp_mb__after_atomic();
		wake_up_bit(&orig_bh->b_state, BH_Shadow);
	}
	unlock_buffer(bh);
}

/*
 * When an ext4 file is truncated, it is possible that some pages are not
 * successfully freed, because they are attached to a committing transaction.
 * After the transaction commits, these pages are left on the LRU, with no
 * ->mapping, and with attached buffers.  These pages are trivially reclaimable
 * by the VM, but their apparent absence upsets the VM accounting, and it makes
 * the numbers in /proc/meminfo look odd.
 *
 * So here, we have a buffer which has just come off the forget list.  Look to
 * see if we can strip all buffers from the backing page.
 *
 * Called under lock_journal(), and possibly under journal_datalist_lock.  The
 * caller provided us with a ref against the buffer, and we drop that here.
 */
static void release_buffer_page(struct buffer_head *bh)
{
	struct folio *folio;

	if (buffer_dirty(bh))
		goto nope;
	if (atomic_read(&bh->b_count) != 1)
		goto nope;
	folio = bh->b_folio;
	if (folio->mapping)
		goto nope;

	/* OK, it's a truncated page */
	if (!folio_trylock(folio))
		goto nope;

	folio_get(folio);
	__brelse(bh);
	try_to_free_buffers(folio);
	folio_unlock(folio);
	folio_put(folio);
	return;

nope:
	__brelse(bh);
}

static void jbd2_commit_block_csum_set(journal_t *j, struct buffer_head *bh)
{
	struct commit_header *h;
	__u32 csum;

	if (!jbd2_journal_has_csum_v2or3(j))
		return;

	h = (struct commit_header *)(bh->b_data);
	h->h_chksum_type = 0;
	h->h_chksum_size = 0;
	h->h_chksum[0] = 0;
	csum = jbd2_chksum(j, j->j_csum_seed, bh->b_data, j->j_blocksize);
	h->h_chksum[0] = cpu_to_be32(csum);
}

/*
 * Done it all: now submit the commit record.  We should have
 * cleaned up our previous buffers by now, so if we are in abort
 * mode we can now just skip the rest of the journal write
 * entirely.
 *
 * Returns 1 if the journal needs to be aborted or 0 on success
 */
static int journal_submit_commit_record(journal_t *journal,
					transaction_t *commit_transaction,
					struct buffer_head **cbh,
					__u32 crc32_sum)
{
	struct commit_header *tmp;
	struct buffer_head *bh;
	struct timespec64 now;
	blk_opf_t write_flags = REQ_OP_WRITE | JBD2_JOURNAL_REQ_FLAGS;

	*cbh = NULL;

	if (is_journal_aborted(journal))
		return 0;

	bh = jbd2_journal_get_descriptor_buffer(commit_transaction,
						JBD2_COMMIT_BLOCK);
	if (!bh)
		return 1;

	tmp = (struct commit_header *)bh->b_data;
	ktime_get_coarse_real_ts64(&now);
	tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
	tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);

	if (jbd2_has_feature_checksum(journal)) {
		tmp->h_chksum_type 	= JBD2_CRC32_CHKSUM;
		tmp->h_chksum_size 	= JBD2_CRC32_CHKSUM_SIZE;
		tmp->h_chksum[0] 	= cpu_to_be32(crc32_sum);
	}
	jbd2_commit_block_csum_set(journal, bh);

	BUFFER_TRACE(bh, "submit commit block");
	lock_buffer(bh);
	clear_buffer_dirty(bh);
	set_buffer_uptodate(bh);
	bh->b_end_io = journal_end_buffer_io_sync;

	if (journal->j_flags & JBD2_BARRIER &&
	    !jbd2_has_feature_async_commit(journal))
		write_flags |= REQ_PREFLUSH | REQ_FUA;

	submit_bh(write_flags, bh);
	*cbh = bh;