[PATCH 07/10] afs: Fix where page->private is set during write

David Howells
2020-10-27T13:51:01Z

In afs, page->private is set to indicate the dirty region of a page. This
is done in afs_write_begin(), but that can't take account of whether the
copy into the page actually worked.

Fix this by moving the change of page->private into afs_write_end().

Fixes: 4343d00872e1 ("afs: Get rid of the afs_writeback record")
Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/afs/write.c | 41 +++++++++++++++++++++++++++--------------
1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 16a896096ccf..5ed5df906744 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -135,22 +135,8 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
(to < f || from > t))
goto flush_conflicting_write;
- if (from < f)
- f = from;
- if (to > t)
- t = to;
- } else {
- f = from;
- t = to;
}

- priv = (unsigned long)t << AFS_PRIV_SHIFT;
- priv |= f;
- trace_afs_page_dirty(vnode, tracepoint_string("begin"),
- page->index, priv);
- if (!TestSetPagePrivate(page))
- get_page(page);
- set_page_private(page, priv);
*_page = page;
_leave(" = 0");
return 0;
@@ -184,6 +170,9 @@ int afs_write_end(struct file *file, struct address_space *mapping,
{
struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
struct key *key = afs_file_key(file);
+ unsigned long priv;
+ unsigned int f, from = pos & (PAGE_SIZE - 1);
+ unsigned int t, to = from + copied;
loff_t i_size, maybe_i_size;
int ret;

@@ -215,6 +204,30 @@ int afs_write_end(struct file *file, struct address_space *mapping,
SetPageUptodate(page);
}

+ if (PagePrivate(page)) {
+ priv = page_private(page);
+ f = priv & AFS_PRIV_MAX;
+ t = priv >> AFS_PRIV_SHIFT;
+ if (from < f)
+ f = from;
+ if (to > t)
+ t = to;
+ priv = (unsigned long)t << AFS_PRIV_SHIFT;
+ priv |= f;
+ trace_afs_page_dirty(vnode, tracepoint_string("dirty+"),
+ page->index, priv);
+ } else {
+ SetPagePrivate(page);
+ get_page(page);
+ f = from;
+ t = to;
+ priv = (unsigned long)t << AFS_PRIV_SHIFT;
+ priv |= f;
+ trace_afs_page_dirty(vnode, tracepoint_string("dirty"),
+ page->index, priv);
+ }
+
+ set_page_private(page, priv);
set_page_dirty(page);
if (PageDirty(page))
_debug("dirtied");