From 7020933156ac2a8a7386314933e49948bf0438f7 Mon Sep 17 00:00:00 2001 From: Russell Cattelan Date: Thu, 9 Nov 2006 11:28:08 -0500 Subject: [PATCH] [GFS2] Fix race in logging code The log lock is dropped prior to io submittion, but this exposes a hole in which the log data structures may be going away due to a truncate. Store the buffer head in a local pointer prior to dropping the lock and relay on the buffer_head lock for consitency on the buffer head. Signed-Off-By: Russell Cattelan Signed-off-by: Steven Whitehouse --- fs/gfs2/lops.c | 36 +++++++++++++++++++++--------------- 1 file changed, 21 insertions(+), 15 deletions(-) diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c index 8a654cd253d..4d7f94d8c7b 100644 --- a/fs/gfs2/lops.c +++ b/fs/gfs2/lops.c @@ -509,7 +509,7 @@ static void databuf_lo_before_commit(struct gfs2_sbd *sdp) { LIST_HEAD(started); struct gfs2_bufdata *bd1 = NULL, *bd2, *bdt; - struct buffer_head *bh = NULL; + struct buffer_head *bh = NULL,*bh1 = NULL; unsigned int offset = sizeof(struct gfs2_log_descriptor); struct gfs2_log_descriptor *ld; unsigned int limit; @@ -537,8 +537,13 @@ static void databuf_lo_before_commit(struct gfs2_sbd *sdp) list_for_each_entry_safe_continue(bd1, bdt, &sdp->sd_log_le_databuf, bd_le.le_list) { + /* store off the buffer head in a local ptr since + * gfs2_bufdata might change when we drop the log lock + */ + bh1 = bd1->bd_bh; + /* An ordered write buffer */ - if (bd1->bd_bh && !buffer_pinned(bd1->bd_bh)) { + if (bh1 && !buffer_pinned(bh1)) { list_move(&bd1->bd_le.le_list, &started); if (bd1 == bd2) { bd2 = NULL; @@ -547,20 +552,21 @@ static void databuf_lo_before_commit(struct gfs2_sbd *sdp) bd_le.le_list); } total_dbuf--; - if (bd1->bd_bh) { - get_bh(bd1->bd_bh); - if (buffer_dirty(bd1->bd_bh)) { + if (bh1) { + if (buffer_dirty(bh1)) { + get_bh(bh1); + gfs2_log_unlock(sdp); - wait_on_buffer(bd1->bd_bh); - ll_rw_block(WRITE, 1, - &bd1->bd_bh); + + ll_rw_block(SWRITE, 1, &bh1); + brelse(bh1); + gfs2_log_lock(sdp); } - brelse(bd1->bd_bh); continue; } continue; - } else if (bd1->bd_bh) { /* A journaled buffer */ + } else if (bh1) { /* A journaled buffer */ int magic; gfs2_log_unlock(sdp); if (!bh) { @@ -582,16 +588,16 @@ static void databuf_lo_before_commit(struct gfs2_sbd *sdp) ld->ld_data2 = cpu_to_be32(0); memset(ld->ld_reserved, 0, sizeof(ld->ld_reserved)); } - magic = gfs2_check_magic(bd1->bd_bh); - *ptr++ = cpu_to_be64(bd1->bd_bh->b_blocknr); + magic = gfs2_check_magic(bh1); + *ptr++ = cpu_to_be64(bh1->b_blocknr); *ptr++ = cpu_to_be64((__u64)magic); - clear_buffer_escaped(bd1->bd_bh); + clear_buffer_escaped(bh1); if (unlikely(magic != 0)) - set_buffer_escaped(bd1->bd_bh); + set_buffer_escaped(bh1); gfs2_log_lock(sdp); if (n++ > num) break; - } else if (!bd1->bd_bh) { + } else if (!bh1) { total_dbuf--; sdp->sd_log_num_databuf--; list_del_init(&bd1->bd_le.le_list); -- 2.41.1