[PATCH 5.5 211/367] gfs2: fix O_SYNC write handling

Greg Kroah-Hartman
2020-02-10T12:58:31Z

From: Andreas Gruenbacher <agruenba@redhat.com>

commit 6e5e41e2dc4e4413296d5a4af54ac92d7cd52317 upstream.

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: 967bcc91b044 ("gfs2: iomap direct I/O support")
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/gfs2/file.c | 51 +++++++++++++++++++++------------------------------
1 file changed, 21 insertions(+), 30 deletions(-)

--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -847,7 +847,7 @@ static ssize_t gfs2_file_write_iter(stru
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(stru

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,