gfs2: fix O_SYNC write handling

In gfs2_file_write_iter, for direct writes, the error checking in the buffered
write fallback case is incomplete.  This can cause inode write errors to go
undetected.  Fix and clean up gfs2_file_write_iter along the way.

Based on a proposed fix by Christoph Hellwig <hch@lst.de>.

Fixes: d11a253b7541 ("gfs2: iomap direct I/O support")
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 21d032c4b077fd81b8cb222e66104bb68e114d19..cb26be6f4351ffa3f879cb153e0ac23df9d05e36 100644 (file)
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -847,7 +847,7 @@ static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
        struct file *file = iocb->ki_filp;
        struct inode *inode = file_inode(file);
        struct gfs2_inode *ip = GFS2_I(inode);
-       ssize_t written = 0, ret;
+       ssize_t ret;
 
        ret = gfs2_rsqa_alloc(ip);
        if (ret)
@@ -879,55 +879,46 @@ static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
        if (iocb->ki_flags & IOCB_DIRECT) {
                struct address_space *mapping = file->f_mapping;
-               loff_t pos, endbyte;
-               ssize_t buffered;
+               ssize_t buffered, ret2;
 
-               written = gfs2_file_direct_write(iocb, from);
-               if (written < 0 || !iov_iter_count(from))
+               ret = gfs2_file_direct_write(iocb, from);
+               if (ret < 0 || !iov_iter_count(from))
                        goto out_unlock;
 
+               iocb->ki_flags |= IOCB_DSYNC;
                current->backing_dev_info = inode_to_bdi(inode);
-               ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
+               buffered = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
                current->backing_dev_info = NULL;
-               if (unlikely(ret < 0))
+               if (unlikely(buffered <= 0))
                        goto out_unlock;
-               buffered = ret;
 
                /*
                 * We need to ensure that the page cache pages are written to
                 * disk and invalidated to preserve the expected O_DIRECT
-                * semantics.
+                * semantics.  If the writeback or invalidate fails, only report
+                * the direct I/O range as we don't know if the buffered pages
+                * made it to disk.
                 */
-               pos = iocb->ki_pos;
-               endbyte = pos + buffered - 1;
-               ret = filemap_write_and_wait_range(mapping, pos, endbyte);
-               if (!ret) {
-                       iocb->ki_pos += buffered;
-                       written += buffered;
-                       invalidate_mapping_pages(mapping,
-                                                pos >> PAGE_SHIFT,
-                                                endbyte >> PAGE_SHIFT);
-               } else {
-                       /*
-                        * We don't know how much we wrote, so just return
-                        * the number of bytes which were direct-written
-                        */
-               }
+               iocb->ki_pos += buffered;
+               ret2 = generic_write_sync(iocb, buffered);
+               invalidate_mapping_pages(mapping,
+                               (iocb->ki_pos - buffered) >> PAGE_SHIFT,
+                               (iocb->ki_pos - 1) >> PAGE_SHIFT);
+               if (!ret || ret2 > 0)
+                       ret += ret2;
        } else {
                current->backing_dev_info = inode_to_bdi(inode);
                ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
                current->backing_dev_info = NULL;
-               if (likely(ret > 0))
+               if (likely(ret > 0)) {
                        iocb->ki_pos += ret;
+                       ret = generic_write_sync(iocb, ret);
+               }
        }
 
 out_unlock:
        inode_unlock(inode);
-       if (likely(ret > 0)) {
-               /* Handle various SYNC-type writes */
-               ret = generic_write_sync(iocb, ret);
-       }
-       return written ? written : ret;
+       return ret;
 }
 
 static int fallocate_chunk(struct inode *inode, loff_t offset, loff_t len,