gfs2: Fix iomap write page reclaim deadlock

Since commit 64bc06bb32ee ("gfs2: iomap buffered write support"), gfs2 is doing
buffered writes by starting a transaction in iomap_begin, writing a range of
pages, and ending that transaction in iomap_end.  This approach suffers from
two problems:

  (1) Any allocations necessary for the write are done in iomap_begin, so when
  the data aren't journaled, there is no need for keeping the transaction open
  until iomap_end.

  (2) Transactions keep the gfs2 log flush lock held.  When
  iomap_file_buffered_write calls balance_dirty_pages, this can end up calling
  gfs2_write_inode, which will try to flush the log.  This requires taking the
  log flush lock which is already held, resulting in a deadlock.

Fix both of these issues by not keeping transactions open from iomap_begin to
iomap_end.  Instead, start a small transaction in page_prepare and end it in
page_done when necessary.

Reported-by: Edwin Török <edvin.torok@citrix.com>
Fixes: 64bc06bb32ee ("gfs2: iomap buffered write support")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 05dd78f4b2b3b5aa6982d8475be770d4a37f712c..6210d4429d8454030f7a82b4f5c373ca56ccb986 100644 (file)
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -649,7 +649,7 @@ out_uninit:
  */
 void adjust_fs_space(struct inode *inode)
 {
-       struct gfs2_sbd *sdp = inode->i_sb->s_fs_info;
+       struct gfs2_sbd *sdp = GFS2_SB(inode);
        struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
        struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
        struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
@@ -657,10 +657,13 @@ void adjust_fs_space(struct inode *inode)
        struct buffer_head *m_bh, *l_bh;
        u64 fs_total, new_free;
 
+       if (gfs2_trans_begin(sdp, 2 * RES_STATFS, 0) != 0)
+               return;
+
        /* Total up the file system space, according to the latest rindex. */
        fs_total = gfs2_ri_total(sdp);
        if (gfs2_meta_inode_buffer(m_ip, &m_bh) != 0)
-               return;
+               goto out;
 
        spin_lock(&sdp->sd_statfs_spin);
        gfs2_statfs_change_in(m_sc, m_bh->b_data +
@@ -675,11 +678,14 @@ void adjust_fs_space(struct inode *inode)
        gfs2_statfs_change(sdp, new_free, new_free, 0);
 
        if (gfs2_meta_inode_buffer(l_ip, &l_bh) != 0)
-               goto out;
+               goto out2;
        update_statfs(sdp, m_bh, l_bh);
        brelse(l_bh);
-out:
+out2:
        brelse(m_bh);
+out:
+       sdp->sd_rindex_uptodate = 0;
+       gfs2_trans_end(sdp);
 }
 
 /**

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 6f1f0d30fe29cea0264bb2009ecb4900661a85a0..f42718dd292f445c0bfe9da0b5e8703facb24d3b 100644 (file)
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -991,17 +991,28 @@ static void gfs2_write_unlock(struct inode *inode)
        gfs2_glock_dq_uninit(&ip->i_gh);
 }
 
+static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos,
+                                  unsigned len, struct iomap *iomap)
+{
+       struct gfs2_sbd *sdp = GFS2_SB(inode);
+
+       return gfs2_trans_begin(sdp, RES_DINODE + (len >> inode->i_blkbits), 0);
+}
+
 static void gfs2_iomap_page_done(struct inode *inode, loff_t pos,
                                 unsigned copied, struct page *page,
                                 struct iomap *iomap)
 {
        struct gfs2_inode *ip = GFS2_I(inode);
+       struct gfs2_sbd *sdp = GFS2_SB(inode);
 
-       if (page)
+       if (page && !gfs2_is_stuffed(ip))
                gfs2_page_add_databufs(ip, page, offset_in_page(pos), copied);
+       gfs2_trans_end(sdp);
 }
 
 static const struct iomap_page_ops gfs2_iomap_page_ops = {
+       .page_prepare = gfs2_iomap_page_prepare,
        .page_done = gfs2_iomap_page_done,
 };
 
@@ -1057,31 +1068,45 @@ static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos,
        if (alloc_required)
                rblocks += gfs2_rg_blocks(ip, data_blocks + ind_blocks);
 
-       ret = gfs2_trans_begin(sdp, rblocks, iomap->length >> inode->i_blkbits);
-       if (ret)
-               goto out_trans_fail;
+       if (unstuff || iomap->type == IOMAP_HOLE) {
+               struct gfs2_trans *tr;
 
-       if (unstuff) {
-               ret = gfs2_unstuff_dinode(ip, NULL);
+               ret = gfs2_trans_begin(sdp, rblocks,
+                                      iomap->length >> inode->i_blkbits);
                if (ret)
-                       goto out_trans_end;
-               release_metapath(mp);
-               ret = gfs2_iomap_get(inode, iomap->offset, iomap->length,
-                                    flags, iomap, mp);
-               if (ret)
-                       goto out_trans_end;
-       }
+                       goto out_trans_fail;
 
-       if (iomap->type == IOMAP_HOLE) {
-               ret = gfs2_iomap_alloc(inode, iomap, flags, mp);
-               if (ret) {
-                       gfs2_trans_end(sdp);
-                       gfs2_inplace_release(ip);
-                       punch_hole(ip, iomap->offset, iomap->length);
-                       goto out_qunlock;
+               if (unstuff) {
+                       ret = gfs2_unstuff_dinode(ip, NULL);
+                       if (ret)
+                               goto out_trans_end;
+                       release_metapath(mp);
+                       ret = gfs2_iomap_get(inode, iomap->offset,
+                                            iomap->length, flags, iomap, mp);
+                       if (ret)
+                               goto out_trans_end;
+               }
+
+               if (iomap->type == IOMAP_HOLE) {
+                       ret = gfs2_iomap_alloc(inode, iomap, flags, mp);
+                       if (ret) {
+                               gfs2_trans_end(sdp);
+                               gfs2_inplace_release(ip);
+                               punch_hole(ip, iomap->offset, iomap->length);
+                               goto out_qunlock;
+                       }
                }
+
+               tr = current->journal_info;
+               if (tr->tr_num_buf_new)
+                       __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
+               else
+                       gfs2_trans_add_meta(ip->i_gl, mp->mp_bh[0]);
+
+               gfs2_trans_end(sdp);
        }
-       if (!gfs2_is_stuffed(ip) && gfs2_is_jdata(ip))
+
+       if (gfs2_is_stuffed(ip) || gfs2_is_jdata(ip))
                iomap->page_ops = &gfs2_iomap_page_ops;
        return 0;
 
@@ -1121,10 +1146,6 @@ static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
                    iomap->type != IOMAP_MAPPED)
                        ret = -ENOTBLK;
        }
-       if (!ret) {
-               get_bh(mp.mp_bh[0]);
-               iomap->private = mp.mp_bh[0];
-       }
        release_metapath(&mp);
        trace_gfs2_iomap_end(ip, iomap, ret);
        return ret;
@@ -1135,27 +1156,16 @@ static int gfs2_iomap_end(struct inode *inode, loff_t pos, loff_t length,
 {
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
-       struct gfs2_trans *tr = current->journal_info;
-       struct buffer_head *dibh = iomap->private;
 
        if ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) != IOMAP_WRITE)
                goto out;
 
-       if (iomap->type != IOMAP_INLINE) {
+       if (!gfs2_is_stuffed(ip))
                gfs2_ordered_add_inode(ip);
 
-               if (tr->tr_num_buf_new)
-                       __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
-               else
-                       gfs2_trans_add_meta(ip->i_gl, dibh);
-       }
-
-       if (inode == sdp->sd_rindex) {
+       if (inode == sdp->sd_rindex)
                adjust_fs_space(inode);
-               sdp->sd_rindex_uptodate = 0;
-       }
 
-       gfs2_trans_end(sdp);
        gfs2_inplace_release(ip);
 
        if (length != written && (iomap->flags & IOMAP_F_NEW)) {
@@ -1175,8 +1185,6 @@ static int gfs2_iomap_end(struct inode *inode, loff_t pos, loff_t length,
        gfs2_write_unlock(inode);
 
 out:
-       if (dibh)
-               brelse(dibh);
        return 0;
 }