From: Miao Xie <miaox@cn.fujitsu.com>
To: linux-btrfs@vger.kernel.org
Subject: [PATCH 1/9] Btrfs: use ACCESS_ONCE to prevent the optimize accesses to ->last_trans_log_full_commit
Date: Thu, 20 Feb 2014 18:08:51 +0800 [thread overview]
Message-ID: <1392890939-19044-1-git-send-email-miaox@cn.fujitsu.com> (raw)
->last_trans_log_full_commit may be changed by the other tasks without lock,
so we need prevent the compiler from the optimize access just like
tmp = fs_info->last_trans_log_full_commit
if (tmp == ...)
...
<do something>
if (tmp == ...)
...
In fact, we need get the new value of ->last_trans_log_full_commit during
the second access. Fix it by ACCESS_ONCE().
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
fs/btrfs/tree-log.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 7c449c6..5a4e10b 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2375,14 +2375,14 @@ static int wait_log_commit(struct btrfs_trans_handle *trans,
&wait, TASK_UNINTERRUPTIBLE);
mutex_unlock(&root->log_mutex);
- if (root->fs_info->last_trans_log_full_commit !=
+ if (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) !=
trans->transid && root->log_transid < transid + 2 &&
atomic_read(&root->log_commit[index]))
schedule();
finish_wait(&root->log_commit_wait[index], &wait);
mutex_lock(&root->log_mutex);
- } while (root->fs_info->last_trans_log_full_commit !=
+ } while (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) !=
trans->transid && root->log_transid < transid + 2 &&
atomic_read(&root->log_commit[index]));
return 0;
@@ -2392,12 +2392,12 @@ static void wait_for_writer(struct btrfs_trans_handle *trans,
struct btrfs_root *root)
{
DEFINE_WAIT(wait);
- while (root->fs_info->last_trans_log_full_commit !=
+ while (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) !=
trans->transid && atomic_read(&root->log_writers)) {
prepare_to_wait(&root->log_writer_wait,
&wait, TASK_UNINTERRUPTIBLE);
mutex_unlock(&root->log_mutex);
- if (root->fs_info->last_trans_log_full_commit !=
+ if (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) !=
trans->transid && atomic_read(&root->log_writers))
schedule();
mutex_lock(&root->log_mutex);
@@ -2456,7 +2456,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
}
/* bail out if we need to do a full commit */
- if (root->fs_info->last_trans_log_full_commit == trans->transid) {
+ if (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) ==
+ trans->transid) {
ret = -EAGAIN;
btrfs_free_logged_extents(log, log_transid);
mutex_unlock(&root->log_mutex);
@@ -2515,7 +2516,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
mutex_unlock(&log_root_tree->log_mutex);
goto out;
}
- root->fs_info->last_trans_log_full_commit = trans->transid;
+ ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) =
+ trans->transid;
btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
btrfs_free_logged_extents(log, log_transid);
mutex_unlock(&log_root_tree->log_mutex);
@@ -2547,7 +2549,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
* now that we've moved on to the tree of log tree roots,
* check the full commit flag again
*/
- if (root->fs_info->last_trans_log_full_commit == trans->transid) {
+ if (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) ==
+ trans->transid) {
blk_finish_plug(&plug);
btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
btrfs_free_logged_extents(log, log_transid);
--
1.8.1.4
next reply other threads:[~2014-02-20 10:07 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-20 10:08 Miao Xie [this message]
2014-02-20 10:08 ` [PATCH 2/9] Btrfs: fix the skipped transaction commit during the file sync Miao Xie
2014-02-20 10:08 ` [PATCH 3/9] Btrfs: don't start the log transaction if the log tree init fails Miao Xie
2014-02-20 10:08 ` [PATCH 4/9] Btrfs: use bitfield instead of integer data type for the some variants in btrfs_root Miao Xie
2014-02-22 0:23 ` David Sterba
2014-02-26 9:10 ` Miao Xie
2014-02-27 17:02 ` David Sterba
2014-03-07 23:54 ` Josef Bacik
2014-03-08 0:00 ` Josef Bacik
2014-03-10 1:16 ` Miao Xie
2014-02-20 10:08 ` [PATCH 5/9] Btrfs: remove unnecessary memory barrier in btrfs_sync_log() Miao Xie
2014-02-20 10:08 ` [PATCH 6/9] Btrfs: use signed integer instead of unsigned long integer for log transid Miao Xie
2014-02-20 10:08 ` [PATCH 7/9] Btrfs: stop joining the log transaction if sync log fails Miao Xie
2014-02-22 0:27 ` David Sterba
2014-02-26 8:51 ` Miao Xie
2014-02-20 10:08 ` [PATCH 8/9] Btrfs: fix skipped error handle when log sync failed Miao Xie
2014-02-20 10:08 ` [PATCH 9/9] Btrfs: just wait or commit our own log sub-transaction Miao Xie
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1392890939-19044-1-git-send-email-miaox@cn.fujitsu.com \
--to=miaox@cn.fujitsu.com \
--cc=linux-btrfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox