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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: Jan Kara <jack@suse.cz>
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201106035911.1942128-9-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Harshad Shirwadkar 2020-11-05 19:58:57 -08:00 committed by Theodore Ts'o
parent 37e0a30e94
commit c460e5edc8
2 changed files with 6 additions and 10 deletions
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6
fs/jbd2/journal.c
View File

@ -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

10
include/linux/jbd2.h
View File

@ -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;