gfs2: Remove active journal side effect from gfs2_write_log_header

Function gfs2_write_log_header can be used to write a log header into any of
the journals of a filesystem.  When used on the node's own journal,
gfs2_write_log_header advances the current position in the log
(sdp->sd_log_flush_head) as a side effect, through function gfs2_log_bmap.

This is confusing, and it also means that we can't use gfs2_log_bmap for other
journals even if they have an extent map.  So clean this mess up by not
advancing sdp->sd_log_flush_head in gfs2_write_log_header or gfs2_log_bmap
anymore and making that a responsibility of the callers instead.

This is related to commit 7c70b896 ("gfs2: clean_journal improperly set
sd_log_flush_head").
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/log.c

@@ -707,7 +707,7 @@ void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
 	lh->lh_nsec = cpu_to_be32(tv.tv_nsec);
 	lh->lh_sec = cpu_to_be64(tv.tv_sec);
 	if (!list_empty(&jd->extent_list))
-		dblock = gfs2_log_bmap(sdp);
+		dblock = gfs2_log_bmap(jd, lblock);
 	else {
 		int ret = gfs2_lblk_to_dblk(jd->jd_inode, lblock, &dblock);
 		if (gfs2_assert_withdraw(sdp, ret == 0))
@@ -768,6 +768,7 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
 	sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
 	gfs2_write_log_header(sdp, sdp->sd_jdesc, sdp->sd_log_sequence++, tail,
 			      sdp->sd_log_flush_head, flags, op_flags);
+	gfs2_log_incr_head(sdp);
 
 	if (sdp->sd_log_tail != tail)
 		log_pull_tail(sdp, tail);

fs/gfs2/lops.c

@@ -129,7 +129,7 @@ static void gfs2_unpin(struct gfs2_sbd *sdp, struct buffer_head *bh,
 	atomic_dec(&sdp->sd_log_pinned);
 }
 
-static void gfs2_log_incr_head(struct gfs2_sbd *sdp)
+void gfs2_log_incr_head(struct gfs2_sbd *sdp)
 {
 	BUG_ON((sdp->sd_log_flush_head == sdp->sd_log_tail) &&
 	       (sdp->sd_log_flush_head != sdp->sd_log_head));
@@ -138,18 +138,13 @@ static void gfs2_log_incr_head(struct gfs2_sbd *sdp)
 		sdp->sd_log_flush_head = 0;
 }
 
-u64 gfs2_log_bmap(struct gfs2_sbd *sdp)
+u64 gfs2_log_bmap(struct gfs2_jdesc *jd, unsigned int lblock)
 {
-	unsigned int lbn = sdp->sd_log_flush_head;
 	struct gfs2_journal_extent *je;
-	u64 block;
 
-	list_for_each_entry(je, &sdp->sd_jdesc->extent_list, list) {
-		if ((lbn >= je->lblock) && (lbn < (je->lblock + je->blocks))) {
-			block = je->dblock + lbn - je->lblock;
-			gfs2_log_incr_head(sdp);
-			return block;
-		}
+	list_for_each_entry(je, &jd->extent_list, list) {
+		if (lblock >= je->lblock && lblock < je->lblock + je->blocks)
+			return je->dblock + lblock - je->lblock;
 	}
 
 	return -1;
@@ -351,8 +346,11 @@ void gfs2_log_write(struct gfs2_sbd *sdp, struct page *page,
 
 static void gfs2_log_write_bh(struct gfs2_sbd *sdp, struct buffer_head *bh)
 {
-	gfs2_log_write(sdp, bh->b_page, bh->b_size, bh_offset(bh),
-		       gfs2_log_bmap(sdp));
+	u64 dblock;
+
+	dblock = gfs2_log_bmap(sdp->sd_jdesc, sdp->sd_log_flush_head);
+	gfs2_log_incr_head(sdp);
+	gfs2_log_write(sdp, bh->b_page, bh->b_size, bh_offset(bh), dblock);
 }
 
 /**
@@ -369,8 +367,11 @@ static void gfs2_log_write_bh(struct gfs2_sbd *sdp, struct buffer_head *bh)
 void gfs2_log_write_page(struct gfs2_sbd *sdp, struct page *page)
 {
 	struct super_block *sb = sdp->sd_vfs;
-	gfs2_log_write(sdp, page, sb->s_blocksize, 0,
-		       gfs2_log_bmap(sdp));
+	u64 dblock;
+
+	dblock = gfs2_log_bmap(sdp->sd_jdesc, sdp->sd_log_flush_head);
+	gfs2_log_incr_head(sdp);
+	gfs2_log_write(sdp, page, sb->s_blocksize, 0, dblock);
 }
 
 /**

fs/gfs2/lops.h

@@ -18,7 +18,8 @@
 	 ~(2 * sizeof(__be64) - 1))
 
 extern const struct gfs2_log_operations *gfs2_log_ops[];
-extern u64 gfs2_log_bmap(struct gfs2_sbd *sdp);
+extern void gfs2_log_incr_head(struct gfs2_sbd *sdp);
+extern u64 gfs2_log_bmap(struct gfs2_jdesc *jd, unsigned int lbn);
 extern void gfs2_log_write(struct gfs2_sbd *sdp, struct page *page,
 			   unsigned size, unsigned offset, u64 blkno);
 extern void gfs2_log_write_page(struct gfs2_sbd *sdp, struct page *page);

fs/gfs2/recovery.c

@@ -263,11 +263,13 @@ static void clean_journal(struct gfs2_jdesc *jd,
 	u32 lblock = head->lh_blkno;
 
 	gfs2_replay_incr_blk(jd, &lblock);
-	if (jd->jd_jid == sdp->sd_lockstruct.ls_jid)
-		sdp->sd_log_flush_head = lblock;
 	gfs2_write_log_header(sdp, jd, head->lh_sequence + 1, 0, lblock,
 			      GFS2_LOG_HEAD_UNMOUNT | GFS2_LOG_HEAD_RECOVERY,
 			      REQ_PREFLUSH | REQ_FUA | REQ_META | REQ_SYNC);
+	if (jd->jd_jid == sdp->sd_lockstruct.ls_jid) {
+		sdp->sd_log_flush_head = lblock;
+		gfs2_log_incr_head(sdp);
+	}
 }