On Fri, 2014-01-17 at 15:12 -0500, Scott Mayhew wrote: > We should always make sure the cached page is up-to-date when we're > determining whether we can extend a write to cover the full page -- even > if we've received a write delegation from the server. > > Commit c7559663 added logic to skip this check if we have a write > delegation, which can lead to data corruption such as the following > scenario if client B receives a write delegation from the NFS server: > > Client A: > # echo 123456789 > /mnt/file > > Client B: > # echo abcdefghi >> /mnt/file > # cat /mnt/file > 0�D0�abcdefghi > > Just because we hold a write delegation doesn't mean that we've read in > the entire page contents. > > Cc: <[email protected]> # v3.11+ > Signed-off-by: Scott Mayhew <[email protected]> > --- > fs/nfs/write.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/fs/nfs/write.c b/fs/nfs/write.c > index c1d5482..6a85038 100644 > --- a/fs/nfs/write.c > +++ b/fs/nfs/write.c > @@ -922,19 +922,20 @@ out: > * extend the write to cover the entire page in order to avoid fragmentation > * inefficiencies. > * > - * If the file is opened for synchronous writes or if we have a write > delegation > - * from the server then we can just skip the rest of the checks. > + * If the file is opened for synchronous writes then we can just skip the > rest > + * of the checks. > */ > static int nfs_can_extend_write(struct file *file, struct page *page, struct > inode *inode) > { > if (file->f_flags & O_DSYNC) > return 0; > + if (!nfs_write_pageuptodate(page, inode)) > + return 0; > if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE)) > return 1; > - if (nfs_write_pageuptodate(page, inode) && (inode->i_flock == NULL || > - (inode->i_flock->fl_start == 0 && > + if (inode->i_flock == NULL || (inode->i_flock->fl_start == 0 && > inode->i_flock->fl_end == OFFSET_MAX && > - inode->i_flock->fl_type != F_RDLCK))) > + inode->i_flock->fl_type != F_RDLCK)) > return 1; > return 0; > }
Acked-by: Dave Wysochanski <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
