cifs: Avoid calling unlock_page() twice in cifs_readpage() when using fscache
When reading a single page with cifs_readpage(), we make a call to
fscache_read_or_alloc_page() which once done, asynchronously calls
the completion function cifs_readpage_from_fscache_complete(). This
completion function unlocks the page once it has been populated from
cache. The module then attempts to unlock the page a second time in
cifs_readpage() which leads to warning messages.
In case of a successful call to fscache_read_or_alloc_page() we should skip
the second unlock_page() since this will be called by the
cifs_readpage_from_fscache_complete() once the page has been populated by
fscache.
With the modifications to cifs_readpage_worker(), we will need to re-grab the
page lock in cifs_write_begin().
The problem was first noticed when testing new fscache patches for cifs.
https://bugzilla.redhat.com/show_bug.cgi?id=1005737
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 5f99ee5..eb955b5 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3419,6 +3419,7 @@
io_error:
kunmap(page);
+ unlock_page(page);
read_complete:
return rc;
@@ -3443,8 +3444,6 @@
rc = cifs_readpage_worker(file, page, &offset);
- unlock_page(page);
-
free_xid(xid);
return rc;
}
@@ -3498,6 +3497,7 @@
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
+ int oncethru = 0;
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
loff_t offset = pos & (PAGE_CACHE_SIZE - 1);
loff_t page_start = pos & PAGE_MASK;
@@ -3507,6 +3507,7 @@
cifs_dbg(FYI, "write_begin from %lld len %d\n", (long long)pos, len);
+start:
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page) {
rc = -ENOMEM;
@@ -3548,13 +3549,16 @@
}
}
- if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
+ if ((file->f_flags & O_ACCMODE) != O_WRONLY && !oncethru) {
/*
* might as well read a page, it is fast enough. If we get
* an error, we don't need to return it. cifs_write_end will
* do a sync write instead since PG_uptodate isn't set.
*/
cifs_readpage_worker(file, page, &page_start);
+ page_cache_release(page);
+ oncethru = 1;
+ goto start;
} else {
/* we could try using another file handle if there is one -
but how would we lock it to prevent close of that handle