NFS: Fix a race when updating an existing write

After nfs_lock_and_join_requests() tests for whether the request is
still attached to the mapping, nothing prevents a call to
nfs_inode_remove_request() from succeeding until we actually lock the
page group.
The reason is that whoever called nfs_inode_remove_request() doesn't
necessarily have a lock on the page group head.

So in order to avoid races, let's take the page group lock earlier in
nfs_lock_and_join_requests(), and hold it across the removal of the
request in nfs_inode_remove_request().

Reported-by: Jeff Layton <[email protected]>
Tested-by: Joe Quanaim <[email protected]>
Tested-by: Andrew Steffen <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Fixes: bd37d6fce184 ("NFSv4: Convert nfs_lock_and_join_requests() to use nfs_page_find_head_request()")
Cc: [email protected]
Signed-off-by: Trond Myklebust <[email protected]>

0 files changed, 0 insertions, 0 deletions