NFS: Fix fdatasync/fsync() when confronted with a server reboot
If the server reboots before it can commit the unstable writes to disk,
then nfs_commit_release_pages() will detect this when it compares the
verifier returned by COMMIT to the one returned by WRITE. When this
happens, the client needs to resend those writes in order to guarantee
that they make it to stable storage.
This patch adds a signalling mechanism to notify fsync() that it
needs to retry all writes before it can exit.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 6a7fcab..cc9b566 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -259,7 +259,7 @@
struct dentry *dentry = file->f_path.dentry;
struct nfs_open_context *ctx = nfs_file_open_context(file);
struct inode *inode = dentry->d_inode;
- int have_error, status;
+ int have_error, do_resend, status;
int ret = 0;
dprintk("NFS: fsync file(%s/%s) datasync %d\n",
@@ -267,15 +267,23 @@
datasync);
nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
+ do_resend = test_and_clear_bit(NFS_CONTEXT_RESEND_WRITES, &ctx->flags);
have_error = test_and_clear_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
status = nfs_commit_inode(inode, FLUSH_SYNC);
- if (status >= 0 && ret < 0)
- status = ret;
have_error |= test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
- if (have_error)
+ if (have_error) {
ret = xchg(&ctx->error, 0);
- if (!ret && status < 0)
+ if (ret)
+ goto out;
+ }
+ if (status < 0) {
ret = status;
+ goto out;
+ }
+ do_resend |= test_bit(NFS_CONTEXT_RESEND_WRITES, &ctx->flags);
+ if (do_resend)
+ ret = -EAGAIN;
+out:
return ret;
}
EXPORT_SYMBOL_GPL(nfs_file_fsync_commit);
@@ -286,13 +294,15 @@
int ret;
struct inode *inode = file->f_path.dentry->d_inode;
- ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
- if (ret != 0)
- goto out;
- mutex_lock(&inode->i_mutex);
- ret = nfs_file_fsync_commit(file, start, end, datasync);
- mutex_unlock(&inode->i_mutex);
-out:
+ do {
+ ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+ if (ret != 0)
+ break;
+ mutex_lock(&inode->i_mutex);
+ ret = nfs_file_fsync_commit(file, start, end, datasync);
+ mutex_unlock(&inode->i_mutex);
+ } while (ret == -EAGAIN);
+
return ret;
}
