Sorry for the late reply. On Wed, Aug 14, 2024 at 05:56:06PM +0800, Jingbo Xu wrote: > > > On 8/14/24 5:36 PM, yangyun wrote: > > In some cases, the fi->writepages may be empty. And there is no need > > to check fi->writepages with spin_lock, which may have an impact on > > performance due to lock contention. For example, in scenarios where > > multiple readers read the same file without any writers, or where > > the page cache is not enabled. > > > > Also remove the outdated comment since commit 6b2fb79963fb ("fuse: > > optimize writepages search") has optimize the situation by replacing > > list with rb-tree. > > > > Signed-off-by: yangyun <yangyun50@xxxxxxxxxx> > > --- > > fs/fuse/file.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > > index f39456c65ed7..59c911b61000 100644 > > --- a/fs/fuse/file.c > > +++ b/fs/fuse/file.c > > @@ -448,9 +448,6 @@ static struct fuse_writepage_args *fuse_find_writeback(struct fuse_inode *fi, > > > > /* > > * Check if any page in a range is under writeback > > - * > > - * This is currently done by walking the list of writepage requests > > - * for the inode, which can be pretty inefficient. > > */ > > static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from, > > pgoff_t idx_to) > > @@ -458,6 +455,9 @@ static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from, > > struct fuse_inode *fi = get_fuse_inode(inode); > > bool found; > > > > + if (RB_EMPTY_ROOT(&fi->writepages)) > > + return false; > > fi->lock is held when inserting wpa into fi->writepages rbtree (see > fuse_writepage_add()). I doubt if there is race condition when checking > if fi->writepages rbtree is empty without fi->lock held. The code can make sure that there are no race conditions because: 1. For O_DIRECT and FOPEN_DIRECT_IO with fc->direct_io_allow_mmap, the `filemap_write_and_wait_range` before can make the insert operation to be happend before the check operation. 2. For other cases, there are no pagecache operaions so the fi->writepages is always empty. In my usercase, the fi->writepages is usually empty but the spin_lock associated with it contributes a great impact on the performace of my filesystem due to lock contention. So optimize it. > > -- > Thanks, > Jingbo