NFSv4.1: Fix a race in nfs4_write_inode

nfs4_write_inode() must not be allowed to exit until the layoutcommit
is done. That means that both NFS_INO_LAYOUTCOMMIT and
NFS_INO_LAYOUTCOMMITTING have to be cleared.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

2 files changed, 38 insertions, 43 deletions

diff --git a/fs/nfs/nfs4super.c b/fs/nfs/nfs4super.c
index 65ab0a0ca1c4..808f29574412 100644
--- a/fs/nfs/nfs4super.c
+++ b/fs/nfs/nfs4super.c
@@ -77,17 +77,9 @@ static int nfs4_write_inode(struct inode *inode, struct writeback_control *wbc)
 {
         int ret = nfs_write_inode(inode, wbc);
 
-        if (ret >= 0 && test_bit(NFS_INO_LAYOUTCOMMIT, &NFS_I(inode)->flags)) {
-                int status;
-                bool sync = true;
-
-                if (wbc->sync_mode == WB_SYNC_NONE)
-                        sync = false;
-
-                status = pnfs_layoutcommit_inode(inode, sync);
-                if (status < 0)
-                        return status;
-        }
+        if (ret == 0)
+                ret = pnfs_layoutcommit_inode(inode,
+                                wbc->sync_mode == WB_SYNC_ALL);
         return ret;
 }
 
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index d75d938d36cb..4755858e37a0 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1790,6 +1790,15 @@ pnfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc)
 }
 EXPORT_SYMBOL_GPL(pnfs_generic_pg_readpages);
 
+static void pnfs_clear_layoutcommitting(struct inode *inode)
+{
+        unsigned long *bitlock = &NFS_I(inode)->flags;
+
+        clear_bit_unlock(NFS_INO_LAYOUTCOMMITTING, bitlock);
+        smp_mb__after_clear_bit();
+        wake_up_bit(bitlock, NFS_INO_LAYOUTCOMMITTING);
+}
+
 /*
  * There can be multiple RW segments.
  */
@@ -1807,7 +1816,6 @@ static void pnfs_list_write_lseg(struct inode *inode, struct list_head *listp)
 static void pnfs_list_write_lseg_done(struct inode *inode, struct list_head *listp)
 {
         struct pnfs_layout_segment *lseg, *tmp;
-        unsigned long *bitlock = &NFS_I(inode)->flags;
 
         /* Matched by references in pnfs_set_layoutcommit */
         list_for_each_entry_safe(lseg, tmp, listp, pls_lc_list) {
@@ -1815,9 +1823,7 @@ static void pnfs_list_write_lseg_done(struct inode *inode, struct list_head *lis
                 pnfs_put_lseg(lseg);
         }
 
-        clear_bit_unlock(NFS_INO_LAYOUTCOMMITTING, bitlock);
-        smp_mb__after_clear_bit();
-        wake_up_bit(bitlock, NFS_INO_LAYOUTCOMMITTING);
+        pnfs_clear_layoutcommitting(inode);
 }
 
 void pnfs_set_lo_fail(struct pnfs_layout_segment *lseg)
@@ -1881,43 +1887,37 @@ pnfs_layoutcommit_inode(struct inode *inode, bool sync)
         struct nfs4_layoutcommit_data *data;
         struct nfs_inode *nfsi = NFS_I(inode);
         loff_t end_pos;
-        int status = 0;
+        int status;
 
-        dprintk("--> %s inode %lu\n", __func__, inode->i_ino);
-
-        if (!test_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags))
+        if (!pnfs_layoutcommit_outstanding(inode))
                 return 0;
 
-        /* Note kzalloc ensures data->res.seq_res.sr_slot == NULL */
-        data = kzalloc(sizeof(*data), GFP_NOFS);
-        if (!data) {
-                status = -ENOMEM;
-                goto out;
-        }
-
-        if (!test_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags))
-                goto out_free;
+        dprintk("--> %s inode %lu\n", __func__, inode->i_ino);
 
+        status = -EAGAIN;
         if (test_and_set_bit(NFS_INO_LAYOUTCOMMITTING, &nfsi->flags)) {
-                if (!sync) {
-                        status = -EAGAIN;
-                        goto out_free;
-                }
-                status = wait_on_bit_lock(&nfsi->flags, NFS_INO_LAYOUTCOMMITTING,
-                                        nfs_wait_bit_killable, TASK_KILLABLE);
+                if (!sync)
+                        goto out;
+                status = wait_on_bit_lock(&nfsi->flags,
+                                NFS_INO_LAYOUTCOMMITTING,
+                                nfs_wait_bit_killable,
+                                TASK_KILLABLE);
                 if (status)
-                        goto out_free;
+                        goto out;
         }
 
-        INIT_LIST_HEAD(&data->lseg_list);
+        status = -ENOMEM;
+        /* Note kzalloc ensures data->res.seq_res.sr_slot == NULL */
+        data = kzalloc(sizeof(*data), GFP_NOFS);
+        if (!data)
+                goto clear_layoutcommitting;
+
+        status = 0;
         spin_lock(&inode->i_lock);
-        if (!test_and_clear_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags)) {
-                clear_bit(NFS_INO_LAYOUTCOMMITTING, &nfsi->flags);
-                spin_unlock(&inode->i_lock);
-                wake_up_bit(&nfsi->flags, NFS_INO_LAYOUTCOMMITTING);
-                goto out_free;
-        }
+        if (!test_and_clear_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags))
+                goto out_unlock;
 
+        INIT_LIST_HEAD(&data->lseg_list);
         pnfs_list_write_lseg(inode, &data->lseg_list);
 
         end_pos = nfsi->layout->plh_lwb;
@@ -1940,8 +1940,11 @@ out:
                 mark_inode_dirty_sync(inode);
         dprintk("<-- %s status %d\n", __func__, status);
         return status;
-out_free:
+out_unlock:
+        spin_unlock(&inode->i_lock);
         kfree(data);
+clear_layoutcommitting:
+        pnfs_clear_layoutcommitting(inode);
         goto out;
 }