Merge tag 'v4.4.88' into toradex_vf_4.4-next

This is the 4.4.88 stable release

1 files changed, 20 insertions, 1 deletions

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 187b80267ff9..a9063ac50c4e 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1426,6 +1426,26 @@ __xfs_get_blocks(
 	if (error)
 		goto out_unlock;
 
+	/*
+	 * The only time we can ever safely find delalloc blocks on direct I/O
+	 * is a dio write to post-eof speculative preallocation. All other
+	 * scenarios are indicative of a problem or misuse (such as mixing
+	 * direct and mapped I/O).
+	 *
+	 * The file may be unmapped by the time we get here so we cannot
+	 * reliably fail the I/O based on mapping. Instead, fail the I/O if this
+	 * is a read or a write within eof. Otherwise, carry on but warn as a
+	 * precuation if the file happens to be mapped.
+	 */
+	if (direct && imap.br_startblock == DELAYSTARTBLOCK) {
+	        if (!create || offset < i_size_read(VFS_I(ip))) {
+	                WARN_ON_ONCE(1);
+	                error = -EIO;
+	                goto out_unlock;
+	        }
+	        WARN_ON_ONCE(mapping_mapped(VFS_I(ip)->i_mapping));
+	}
+
 	/* for DAX, we convert unwritten extents directly */
 	if (create &&
 	    (!nimaps ||
@@ -1525,7 +1545,6 @@ __xfs_get_blocks(
 		set_buffer_new(bh_result);
 
 	if (imap.br_startblock == DELAYSTARTBLOCK) {
-		BUG_ON(direct);
 		if (create) {
 			set_buffer_uptodate(bh_result);
 			set_buffer_mapped(bh_result);