Merge tag 'gfs2-4.17.fixes2' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2

4ac1800f · Linus Torvalds <[email protected]> · 2018-04-12 13:00:44 -07:00

Pull more gfs2 updates from Bob Peterson:
 "We decided to request the latest three patches to be merged into this
  merge window while it's still open.

   - The first patch adds a new function to lockref:
     lockref_put_not_zero

   - The second patch fixes GFS2's glock dump code so it uses the new
     lockref function. This fixes a problem whereby lock dumps could
     miss glocks.

   - I made a minor patch to update some comments and fix the lock
     ordering text in our gfs2-glocks.txt Documentation file"

* tag 'gfs2-4.17.fixes2' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
  GFS2: Minor improvements to comments and documentation
  gfs2: Stop using rhashtable_walk_peek
  lockref: Add lockref_put_not_zero

Commit: 4ac1800f81eb52f776aca201e791eec2ef355259
Parents: a1bf4c7d · 3e7aafc3

Merge commit. Changes below are compared with the first parent: a1bf4c7d.

Changes

6 files changed · +62 −23

File	Status	Add	Del	Content
Documentation/filesystems/gfs2-glocks.txt	modified	+3	−2	View file
fs/gfs2/bmap.c	modified	+1	−1	View file
fs/gfs2/glock.c	modified	+28	−19	View file
fs/gfs2/ops_fstype.c	modified	+1	−1	View file
include/linux/lockref.h	modified	+1	−0	View file
lib/lockref.c	modified	+28	−0	View file

Documentation/filesystems/gfs2-glocks.txt

View file

diff --git a/Documentation/filesystems/gfs2-glocks.txt b/Documentation/filesystems/gfs2-glocks.txt
index 1fb12f9..7059623 100644
--- a/Documentation/filesystems/gfs2-glocks.txt
+++ b/Documentation/filesystems/gfs2-glocks.txt
@@ -100,14 +100,15 @@ indicates that it is caching uptodate data.
 
 Glock locking order within GFS2:
 
- 1. i_mutex (if required)
+ 1. i_rwsem (if required)
  2. Rename glock (for rename only)
  3. Inode glock(s)
     (Parents before children, inodes at "same level" with same parent in
      lock number order)
  4. Rgrp glock(s) (for (de)allocation operations)
  5. Transaction glock (via gfs2_trans_begin) for non-read operations
- 6. Page lock  (always last, very important!)
+ 6. i_rw_mutex (if required)
+ 7. Page lock  (always last, very important!)
 
 There are two glocks per inode. One deals with access to the inode
 itself (locking order as above), and the other, known as the iopen

fs/gfs2/bmap.c

View file

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 685c305..278ed08 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -1744,7 +1744,7 @@ do_grow_qunlock:
  * @newsize: the size to make the file
  *
  * The file size can grow, shrink, or stay the same size. This
- * is called holding i_mutex and an exclusive glock on the inode
+ * is called holding i_rwsem and an exclusive glock on the inode
  * in question.
  *
  * Returns: errno

fs/gfs2/glock.c

View file

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 82fb558..097bd3c 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1923,28 +1923,37 @@ void gfs2_glock_exit(void)
 
 static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi, loff_t n)
 {
-	if (n == 0)
-		gi->gl = rhashtable_walk_peek(&gi->hti);
-	else {
-		gi->gl = rhashtable_walk_next(&gi->hti);
-		n--;
+	struct gfs2_glock *gl = gi->gl;
+
+	if (gl) {
+		if (n == 0)
+			return;
+		if (!lockref_put_not_zero(&gl->gl_lockref))
+			gfs2_glock_queue_put(gl);
 	}
 	for (;;) {
-		if (IS_ERR_OR_NULL(gi->gl)) {
-			if (!gi->gl)
-				return;
-			if (PTR_ERR(gi->gl) != -EAGAIN) {
-				gi->gl = NULL;
-				return;
+		gl = rhashtable_walk_next(&gi->hti);
+		if (IS_ERR_OR_NULL(gl)) {
+			if (gl == ERR_PTR(-EAGAIN)) {
+				n = 1;
+				continue;
 			}
-			n = 0;
-		} else if (gi->sdp == gi->gl->gl_name.ln_sbd &&
-			   !__lockref_is_dead(&gi->gl->gl_lockref)) {
-			if (!n--)
-				break;
+			gl = NULL;
+			break;
+		}
+		if (gl->gl_name.ln_sbd != gi->sdp)
+			continue;
+		if (n <= 1) {
+			if (!lockref_get_not_dead(&gl->gl_lockref))
+				continue;
+			break;
+		} else {
+			if (__lockref_is_dead(&gl->gl_lockref))
+				continue;
+			n--;
 		}
-		gi->gl = rhashtable_walk_next(&gi->hti);
 	}
+	gi->gl = gl;
 }
 
 static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
@@ -1988,7 +1997,6 @@ static void gfs2_glock_seq_stop(struct seq_file *seq, void *iter_ptr)
 {
 	struct gfs2_glock_iter *gi = seq->private;
 
-	gi->gl = NULL;
 	rhashtable_walk_stop(&gi->hti);
 }
 
@@ -2076,7 +2084,8 @@ static int gfs2_glocks_release(struct inode *inode, struct file *file)
 	struct seq_file *seq = file->private_data;
 	struct gfs2_glock_iter *gi = seq->private;
 
-	gi->gl = NULL;
+	if (gi->gl)
+		gfs2_glock_put(gi->gl);
 	rhashtable_walk_exit(&gi->hti);
 	return seq_release_private(inode, file);
 }

fs/gfs2/ops_fstype.c

View file

diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index e6a0a8a..3ba3f16 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -825,7 +825,7 @@ static int init_inodes(struct gfs2_sbd *sdp, int undo)
 		goto fail_rindex;
 	}
 	/*
-	 * i_mutex on quota files is special. Since this inode is hidden system
+	 * i_rwsem on quota files is special. Since this inode is hidden system
 	 * file, we are safe to define locking ourselves.
 	 */
 	lockdep_set_class(&sdp->sd_quota_inode->i_rwsem,

include/linux/lockref.h

View file

diff --git a/include/linux/lockref.h b/include/linux/lockref.h
index 2eac320..99f17cc 100644
--- a/include/linux/lockref.h
+++ b/include/linux/lockref.h
@@ -37,6 +37,7 @@ struct lockref {
 extern void lockref_get(struct lockref *);
 extern int lockref_put_return(struct lockref *);
 extern int lockref_get_not_zero(struct lockref *);
+extern int lockref_put_not_zero(struct lockref *);
 extern int lockref_get_or_lock(struct lockref *);
 extern int lockref_put_or_lock(struct lockref *);
 

lib/lockref.c

View file

diff --git a/lib/lockref.c b/lib/lockref.c
index 47169ed..3d468b5 100644
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -81,6 +81,34 @@ int lockref_get_not_zero(struct lockref *lockref)
 EXPORT_SYMBOL(lockref_get_not_zero);
 
 /**
+ * lockref_put_not_zero - Decrements count unless count <= 1 before decrement
+ * @lockref: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count would become zero
+ */
+int lockref_put_not_zero(struct lockref *lockref)
+{
+	int retval;
+
+	CMPXCHG_LOOP(
+		new.count--;
+		if (old.count <= 1)
+			return 0;
+	,
+		return 1;
+	);
+
+	spin_lock(&lockref->lock);
+	retval = 0;
+	if (lockref->count > 1) {
+		lockref->count--;
+		retval = 1;
+	}
+	spin_unlock(&lockref->lock);
+	return retval;
+}
+EXPORT_SYMBOL(lockref_put_not_zero);
+
+/**
  * lockref_get_or_lock - Increments count unless the count is 0 or dead
  * @lockref: pointer to lockref structure
  * Return: 1 if count updated successfully or 0 if count was zero