jbd2: Completely fill journal descriptor blocks (b90bfdf5) · Commits · 戴 / test

With 32-bit block numbers, we don't allocate the array for journal buffer heads large enough for corresponding descriptor tags to fill the descriptor block. Thus we end up writing out half-full descriptor blocks to the journal unnecessarily growing the transaction. Fix the logic to allocate the array large enough. Signed-off-by:

Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20191105164437.32602-3-jack@suse.cz Signed-off-by:

Theodore Ts'o <tytso@mit.edu>

fs/jbd2/journal.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -1098,6 +1098,16 @@ static void jbd2_stats_proc_exit(journal_t *journal)
		remove_proc_entry(journal->j_devname, proc_jbd2_stats);
		}

		/* Minimum size of descriptor tag */
		static int jbd2_min_tag_size(void)
		{
		/*
		* Tag with 32-bit block numbers does not use last four bytes of the
		* structure
		*/
		return sizeof(journal_block_tag_t) - 4;
		}

		/*
		* Management for journal control blocks: functions to create and
		* destroy journal_t structures, and to initialise and read existing
		@@ -1156,7 +1166,8 @@ static journal_t journal_init_common(struct block_device bdev,
		journal->j_fs_dev = fs_dev;
		journal->j_blk_offset = start;
		journal->j_maxlen = len;
		n = journal->j_blocksize / sizeof(journal_block_tag_t);
		/* We need enough buffers to write out full descriptor block. */
		n = journal->j_blocksize / jbd2_min_tag_size();
		journal->j_wbufsize = n;
		journal->j_wbuf = kmalloc_array(n, sizeof(struct buffer_head *),
		GFP_KERNEL);

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