Commit c460e5ed authored by Harshad Shirwadkar's avatar Harshad Shirwadkar Committed by Theodore Ts'o
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jbd2: don't use state lock during commit path 



Variables journal->j_fc_off, journal->j_fc_wbuf are accessed during
commit path. Since today we allow only one process to perform a fast
commit, there is no need take state lock before accessing these
variables. This patch removes these locks and adds comments to
describe this.

Suggested-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarHarshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201106035911.1942128-9-harshadshirwadkar@gmail.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 37e0a30e

fs/jbd2/journal.c

+0 −6
Original line number Diff line number Diff line
@@ -865,7 +865,6 @@ int jbd2_fc_get_buf(journal_t *journal, struct buffer_head **bh_out) 
	int fc_off;



	*bh_out = NULL;

	write_lock(&journal->j_state_lock);



	if (journal->j_fc_off + journal->j_fc_first < journal->j_fc_last) {

		fc_off = journal->j_fc_off;
@@ -874,7 +873,6 @@ int jbd2_fc_get_buf(journal_t *journal, struct buffer_head **bh_out) 
	} else {

		ret = -EINVAL;

	}

	write_unlock(&journal->j_state_lock);



	if (ret)

		return ret;
@@ -909,9 +907,7 @@ int jbd2_fc_wait_bufs(journal_t *journal, int num_blks) 
	struct buffer_head *bh;

	int i, j_fc_off;



	read_lock(&journal->j_state_lock);

	j_fc_off = journal->j_fc_off;

	read_unlock(&journal->j_state_lock);



	/*

	 * Wait in reverse order to minimize chances of us being woken up before
@@ -939,9 +935,7 @@ int jbd2_fc_release_bufs(journal_t *journal) 
	struct buffer_head *bh;

	int i, j_fc_off;



	read_lock(&journal->j_state_lock);

	j_fc_off = journal->j_fc_off;

	read_unlock(&journal->j_state_lock);



	/*

	 * Wait in reverse order to minimize chances of us being woken up before

include/linux/jbd2.h

+6 −4
Original line number Diff line number Diff line
@@ -945,8 +945,9 @@ struct journal_s 
	/**

	 * @j_fc_off:

	 *

	 * Number of fast commit blocks currently allocated.

	 * [j_state_lock].

	 * Number of fast commit blocks currently allocated. Accessed only

	 * during fast commit. Currently only process can do fast commit, so

	 * this field is not protected by any lock.

	 */

	unsigned long		j_fc_off;
@@ -1109,8 +1110,9 @@ struct journal_s 
	struct buffer_head	**j_wbuf;



	/**

	 * @j_fc_wbuf: Array of fast commit bhs for

	 * jbd2_journal_commit_transaction.

	 * @j_fc_wbuf: Array of fast commit bhs for fast commit. Accessed only

	 * during a fast commit. Currently only process can do fast commit, so

	 * this field is not protected by any lock.

	 */

	struct buffer_head	**j_fc_wbuf;