From 24972557b12ce8fd5b6c6847d0e2ee1837ddc13b Mon Sep 17 00:00:00 2001 From: Benjamin Marzinski Date: Thu, 1 May 2014 22:26:55 -0500 Subject: GFS2: remove transaction glock GFS2 has a transaction glock, which must be grabbed for every transaction, whose purpose is to deal with freezing the filesystem. Aside from this involving a large amount of locking, it is very easy to make the current fsfreeze code hang on unfreezing. This patch rewrites how gfs2 handles freezing the filesystem. The transaction glock is removed. In it's place is a freeze glock, which is cached (but not held) in a shared state by every node in the cluster when the filesystem is mounted. This lock only needs to be grabbed on freezing, and actions which need to be safe from freezing, like recovery. When a node wants to freeze the filesystem, it grabs this glock exclusively. When the freeze glock state changes on the nodes (either from shared to unlocked, or shared to exclusive), the filesystem does a special log flush. gfs2_log_flush() does all the work for flushing out the and shutting down the incore log, and then it tries to grab the freeze glock in a shared state again. Since the filesystem is stuck in gfs2_log_flush, no new transaction can start, and nothing can be written to disk. Unfreezing the filesytem simply involes dropping the freeze glock, allowing gfs2_log_flush() to grab and then release the shared lock, so it is cached for next time. However, in order for the unfreezing ioctl to occur, gfs2 needs to get a shared lock on the filesystem root directory inode to check permissions. If that glock has already been grabbed exclusively, fsfreeze will be unable to get the shared lock and unfreeze the filesystem. In order to allow the unfreeze, this patch makes gfs2 grab a shared lock on the filesystem root directory during the freeze, and hold it until it unfreezes the filesystem. The functions which need to grab a shared lock in order to allow the unfreeze ioctl to be issued now use the lock grabbed by the freeze code instead. The freeze and unfreeze code take care to make sure that this shared lock will not be dropped while another process is using it. Signed-off-by: Benjamin Marzinski Signed-off-by: Steven Whitehouse --- fs/gfs2/recovery.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) (limited to 'fs/gfs2/recovery.c') diff --git a/fs/gfs2/recovery.c b/fs/gfs2/recovery.c index 7ad4094d68c0..a4ed78b5f47e 100644 --- a/fs/gfs2/recovery.c +++ b/fs/gfs2/recovery.c @@ -454,7 +454,7 @@ void gfs2_recover_func(struct work_struct *work) struct gfs2_inode *ip = GFS2_I(jd->jd_inode); struct gfs2_sbd *sdp = GFS2_SB(jd->jd_inode); struct gfs2_log_header_host head; - struct gfs2_holder j_gh, ji_gh, t_gh; + struct gfs2_holder j_gh, ji_gh, thaw_gh; unsigned long t; int ro = 0; unsigned int pass; @@ -508,11 +508,11 @@ void gfs2_recover_func(struct work_struct *work) t = jiffies; - /* Acquire a shared hold on the transaction lock */ + /* Acquire a shared hold on the freeze lock */ - error = gfs2_glock_nq_init(sdp->sd_trans_gl, LM_ST_SHARED, - LM_FLAG_NOEXP | LM_FLAG_PRIORITY | - GL_NOCACHE, &t_gh); + error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_SHARED, + LM_FLAG_NOEXP | LM_FLAG_PRIORITY, + &thaw_gh); if (error) goto fail_gunlock_ji; @@ -538,7 +538,7 @@ void gfs2_recover_func(struct work_struct *work) fs_warn(sdp, "jid=%u: Can't replay: read-only block " "device\n", jd->jd_jid); error = -EROFS; - goto fail_gunlock_tr; + goto fail_gunlock_thaw; } fs_info(sdp, "jid=%u: Replaying journal...\n", jd->jd_jid); @@ -549,14 +549,14 @@ void gfs2_recover_func(struct work_struct *work) head.lh_blkno, pass); lops_after_scan(jd, error, pass); if (error) - goto fail_gunlock_tr; + goto fail_gunlock_thaw; } error = clean_journal(jd, &head); if (error) - goto fail_gunlock_tr; + goto fail_gunlock_thaw; - gfs2_glock_dq_uninit(&t_gh); + gfs2_glock_dq_uninit(&thaw_gh); t = DIV_ROUND_UP(jiffies - t, HZ); fs_info(sdp, "jid=%u: Journal replayed in %lus\n", jd->jd_jid, t); @@ -572,8 +572,8 @@ void gfs2_recover_func(struct work_struct *work) fs_info(sdp, "jid=%u: Done\n", jd->jd_jid); goto done; -fail_gunlock_tr: - gfs2_glock_dq_uninit(&t_gh); +fail_gunlock_thaw: + gfs2_glock_dq_uninit(&thaw_gh); fail_gunlock_ji: if (jlocked) { gfs2_glock_dq_uninit(&ji_gh); -- cgit v1.2.3-70-g09d2