GFS2: Limit number of transaction blocks requested for truncates

Hi,

On 16 December, I posted a predecessor patch for this problem. Steve Whitehouse had suggested we base the number of allowable blocks on the size of the journal rather than an arbitrary number. This version 2 patch implements that suggestion:
---
GFS2: Limit number of transaction blocks requested for truncates

This patch limits the number of transaction blocks requested during file truncates. If we have very large multi-terabyte files, and want to delete or truncate them, they might span so many resource groups that we overflow the journal blocks, and cause an assert failure. By limiting the number of blocks in the transaction, we prevent this overflow and give other running processes time to do transactions.

Signed-off-by Bob Peterson <[email protected]>

---

fs/gfs2/bmap.c +26 -3

index 645721f..07d6ef1 100644
@@ -720,6 +720,7 @@ static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
  {
  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
  	struct gfs2_rgrp_list rlist;
+	struct gfs2_trans *tr;
  	u64 bn, bstart;
  	u32 blen, btotal;
  	__be64 *p;

@@ -728,6 +729,7 @@ static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
  	unsigned int revokes = 0;
  	int x;
  	int error;
+	int jblocks_rqsted;
 
  	error = gfs2_rindex_update(sdp);
  	if (error)

@@ -791,12 +793,17 @@ static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
  	if (gfs2_rs_active(&ip->i_res)) /* needs to be done with the rgrp glock held */
  		gfs2_rs_deltree(&ip->i_res);
 
-	error = gfs2_trans_begin(sdp, rg_blocks + RES_DINODE +
-				 RES_INDIRECT + RES_STATFS + RES_QUOTA,
-				 revokes);
+restart:
+	jblocks_rqsted = rg_blocks + RES_DINODE +
+		RES_INDIRECT + RES_STATFS + RES_QUOTA +
+		gfs2_struct2blk(sdp, revokes, sizeof(u64));
+	if (jblocks_rqsted > sdp->sd_log_rsrv_max)
+		jblocks_rqsted = sdp->sd_log_rsrv_max;
+	error = gfs2_trans_begin(sdp, jblocks_rqsted, revokes);
  	if (error)
  		goto out_rg_gunlock;
 
+	tr = current->journal_info;
  	down_write(&ip->i_rw_mutex);
 
  	gfs2_trans_add_meta(ip->i_gl, dibh);

@@ -810,6 +817,16 @@ static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
  		if (!*p)
  			continue;
 
+		/* check for max reasonable journal transaction blocks */
+		if (tr->tr_num_buf_new + RES_STATFS +
+		    RES_QUOTA >= sdp->sd_log_rsrv_max) {
+			if (rg_blocks >= tr->tr_num_buf_new)
+				rg_blocks -= tr->tr_num_buf_new;
+			else
+				rg_blocks = 0;
+			break;
+		}
+
  		bn = be64_to_cpu(*p);
 
  		if (bstart + blen == bn)

@@ -827,6 +844,9 @@ static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
  		*p = 0;
  		gfs2_add_inode_blocks(&ip->i_inode, -1);
  	}
+	if (p == bottom)
+		rg_blocks = 0;
+
  	if (bstart) {
  		__gfs2_free_blocks(ip, bstart, blen, metadata);
  		btotal += blen;

@@ -844,6 +864,9 @@ static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
 
  	gfs2_trans_end(sdp);
 
+	if (rg_blocks)
+		goto restart;
+
  out_rg_gunlock:
  	gfs2_glock_dq_m(rlist.rl_rgrps, rlist.rl_ghs);
  out_rlist:

fs/gfs2/incore.h +2 -0

index a6a3389..55b076a 100644
@@ -818,6 +818,8 @@ struct gfs2_sbd {
  	struct list_head sd_ail1_list;
  	struct list_head sd_ail2_list;
 
+	unsigned int sd_log_rsrv_max;
+
  	/* For quiescing the filesystem */
  	struct gfs2_holder sd_freeze_gh;
  	atomic_t sd_freeze_state;

fs/gfs2/super.c +2 -0

index e3ee387..4db5423 100644
@@ -363,6 +363,8 @@ int gfs2_jdesc_check(struct gfs2_jdesc *jd)
  		return -EIO;
 
  	jd->jd_blocks = size >> sdp->sd_sb.sb_bsize_shift;
+	/* Allow transactions to reserve 3/4 of the journal at most */
+	sdp->sd_log_rsrv_max = (jd->jd_blocks >> 1) + (jd->jd_blocks >> 2);
 
  	if (gfs2_write_alloc_required(ip, 0, size)) {
  		gfs2_consist_inode(ip);