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authorBenjamin Marzinski <bmarzins@redhat.com>2014-05-01 22:26:55 -0500
committerSteven Whitehouse <swhiteho@redhat.com>2014-05-14 10:04:34 +0100
commit24972557b12ce8fd5b6c6847d0e2ee1837ddc13b (patch)
treefb82edff8bfab9d4d1c4df6dd7784dd3c9f85c1b /fs/gfs2/glops.c
parent5a7c6690c2759d686d2c299402327e92ed92ab6c (diff)
downloadop-kernel-dev-24972557b12ce8fd5b6c6847d0e2ee1837ddc13b.zip
op-kernel-dev-24972557b12ce8fd5b6c6847d0e2ee1837ddc13b.tar.gz
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 <bmarzins@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs/gfs2/glops.c')
-rw-r--r--fs/gfs2/glops.c51
1 files changed, 32 insertions, 19 deletions
diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index 54b66809..0b52793 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -89,18 +89,23 @@ static void gfs2_ail_empty_gl(struct gfs2_glock *gl)
if (!tr.tr_revokes)
return;
- /* A shortened, inline version of gfs2_trans_begin() */
+ /* A shortened, inline version of gfs2_trans_begin()
+ * tr->alloced is not set since the transaction structure is
+ * on the stack */
tr.tr_reserved = 1 + gfs2_struct2blk(sdp, tr.tr_revokes, sizeof(u64));
tr.tr_ip = (unsigned long)__builtin_return_address(0);
sb_start_intwrite(sdp->sd_vfs);
- gfs2_log_reserve(sdp, tr.tr_reserved);
+ if (gfs2_log_reserve(sdp, tr.tr_reserved) < 0) {
+ sb_end_intwrite(sdp->sd_vfs);
+ return;
+ }
WARN_ON_ONCE(current->journal_info);
current->journal_info = &tr;
__gfs2_ail_flush(gl, 0, tr.tr_revokes);
gfs2_trans_end(sdp);
- gfs2_log_flush(sdp, NULL);
+ gfs2_log_flush(sdp, NULL, NORMAL_FLUSH);
}
void gfs2_ail_flush(struct gfs2_glock *gl, bool fsync)
@@ -121,7 +126,7 @@ void gfs2_ail_flush(struct gfs2_glock *gl, bool fsync)
return;
__gfs2_ail_flush(gl, fsync, max_revokes);
gfs2_trans_end(sdp);
- gfs2_log_flush(sdp, NULL);
+ gfs2_log_flush(sdp, NULL, NORMAL_FLUSH);
}
/**
@@ -144,7 +149,7 @@ static void rgrp_go_sync(struct gfs2_glock *gl)
return;
GLOCK_BUG_ON(gl, gl->gl_state != LM_ST_EXCLUSIVE);
- gfs2_log_flush(sdp, gl);
+ gfs2_log_flush(sdp, gl, NORMAL_FLUSH);
filemap_fdatawrite_range(mapping, gl->gl_vm.start, gl->gl_vm.end);
error = filemap_fdatawait_range(mapping, gl->gl_vm.start, gl->gl_vm.end);
mapping_set_error(mapping, error);
@@ -206,7 +211,7 @@ static void inode_go_sync(struct gfs2_glock *gl)
GLOCK_BUG_ON(gl, gl->gl_state != LM_ST_EXCLUSIVE);
- gfs2_log_flush(gl->gl_sbd, gl);
+ gfs2_log_flush(gl->gl_sbd, gl, NORMAL_FLUSH);
filemap_fdatawrite(metamapping);
if (ip) {
struct address_space *mapping = ip->i_inode.i_mapping;
@@ -253,7 +258,7 @@ static void inode_go_inval(struct gfs2_glock *gl, int flags)
}
if (ip == GFS2_I(gl->gl_sbd->sd_rindex)) {
- gfs2_log_flush(gl->gl_sbd, NULL);
+ gfs2_log_flush(gl->gl_sbd, NULL, NORMAL_FLUSH);
gl->gl_sbd->sd_rindex_uptodate = 0;
}
if (ip && S_ISREG(ip->i_inode.i_mode))
@@ -455,31 +460,39 @@ static void inode_go_dump(struct seq_file *seq, const struct gfs2_glock *gl)
}
/**
- * trans_go_sync - promote/demote the transaction glock
+ * freeze_go_sync - promote/demote the freeze glock
* @gl: the glock
* @state: the requested state
* @flags:
*
*/
-static void trans_go_sync(struct gfs2_glock *gl)
+static void freeze_go_sync(struct gfs2_glock *gl)
{
struct gfs2_sbd *sdp = gl->gl_sbd;
+ DEFINE_WAIT(wait);
- if (gl->gl_state != LM_ST_UNLOCKED &&
+ if (gl->gl_state == LM_ST_SHARED &&
test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags)) {
- gfs2_meta_syncfs(sdp);
- gfs2_log_shutdown(sdp);
+ atomic_set(&sdp->sd_log_freeze, 1);
+ wake_up(&sdp->sd_logd_waitq);
+ do {
+ prepare_to_wait(&sdp->sd_log_frozen_wait, &wait,
+ TASK_UNINTERRUPTIBLE);
+ if (atomic_read(&sdp->sd_log_freeze))
+ io_schedule();
+ } while(atomic_read(&sdp->sd_log_freeze));
+ finish_wait(&sdp->sd_log_frozen_wait, &wait);
}
}
/**
- * trans_go_xmote_bh - After promoting/demoting the transaction glock
+ * freeze_go_xmote_bh - After promoting/demoting the freeze glock
* @gl: the glock
*
*/
-static int trans_go_xmote_bh(struct gfs2_glock *gl, struct gfs2_holder *gh)
+static int freeze_go_xmote_bh(struct gfs2_glock *gl, struct gfs2_holder *gh)
{
struct gfs2_sbd *sdp = gl->gl_sbd;
struct gfs2_inode *ip = GFS2_I(sdp->sd_jdesc->jd_inode);
@@ -512,7 +525,7 @@ static int trans_go_xmote_bh(struct gfs2_glock *gl, struct gfs2_holder *gh)
* Always returns 0
*/
-static int trans_go_demote_ok(const struct gfs2_glock *gl)
+static int freeze_go_demote_ok(const struct gfs2_glock *gl)
{
return 0;
}
@@ -563,10 +576,10 @@ const struct gfs2_glock_operations gfs2_rgrp_glops = {
.go_flags = GLOF_LVB,
};
-const struct gfs2_glock_operations gfs2_trans_glops = {
- .go_sync = trans_go_sync,
- .go_xmote_bh = trans_go_xmote_bh,
- .go_demote_ok = trans_go_demote_ok,
+const struct gfs2_glock_operations gfs2_freeze_glops = {
+ .go_sync = freeze_go_sync,
+ .go_xmote_bh = freeze_go_xmote_bh,
+ .go_demote_ok = freeze_go_demote_ok,
.go_type = LM_TYPE_NONDISK,
};
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