From 8447d848e1dc6d42d1dcd00f133d7715fc732c47 Mon Sep 17 00:00:00 2001 From: Mateusz Guzik Date: Sat, 10 Aug 2024 08:47:53 +0200 Subject: [PATCH] vfs: only read fops once in fops_get/put In do_dentry_open() the usage is: f->f_op = fops_get(inode->i_fop); In generated asm the compiler emits 2 reads from inode->i_fop instead of just one. This popped up due to false-sharing where loads from that offset end up bouncing a cacheline during parallel open. While this is going to be fixed, the spurious load does not need to be there. This makes do_dentry_open() go down from 1177 to 1154 bytes. fops_put() is patched to maintain some consistency. No functional changes. Reviewed-by: Josef Bacik Signed-off-by: Mateusz Guzik Link: https://lore.kernel.org/r/20240810064753.1211441-1-mjguzik@gmail.com Signed-off-by: Christian Brauner --- include/linux/fs.h | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index c0286d479c9d..696c620f90e0 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2553,10 +2553,17 @@ struct super_block *sget(struct file_system_type *type, struct super_block *sget_dev(struct fs_context *fc, dev_t dev); /* Alas, no aliases. Too much hassle with bringing module.h everywhere */ -#define fops_get(fops) \ - (((fops) && try_module_get((fops)->owner) ? (fops) : NULL)) -#define fops_put(fops) \ - do { if (fops) module_put((fops)->owner); } while(0) +#define fops_get(fops) ({ \ + const struct file_operations *_fops = (fops); \ + (((_fops) && try_module_get((_fops)->owner) ? (_fops) : NULL)); \ +}) + +#define fops_put(fops) ({ \ + const struct file_operations *_fops = (fops); \ + if (_fops) \ + module_put((_fops)->owner); \ +}) + /* * This one is to be used *ONLY* from ->open() instances. * fops must be non-NULL, pinned down *and* module dependencies