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jbd2: Completely fill journal descriptor blocks

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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>
This commit is contained in:
Jan Kara 2019-11-05 17:44:09 +01:00 committed by Theodore Ts'o
parent 0db4588945
commit b90bfdf581
1 changed files with 12 additions and 1 deletions
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13
fs/jbd2/journal.c
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@ -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);