proc: spread likely/unlikely a bit

Web:        https://git.kernel.org/torvalds/c/15b158b4e6274351fc3cf652cbabc57104efb547
Commit:     15b158b4e6274351fc3cf652cbabc57104efb547
Parent:     efb1a57d90cae6af1ddd32f1b920c924a711aba5
Refname:    refs/heads/master
Author:     Alexey Dobriyan <[email protected]>
AuthorDate: Tue Feb 6 15:37:28 2018 -0800
Committer:  Linus Torvalds <[email protected]>
CommitDate: Tue Feb 6 18:32:43 2018 -0800

    proc: spread likely/unlikely a bit
    
    use_pde() is used at every open/read/write/...  of every random /proc
    file.  Negative refcount happens only if PDE is being deleted by module
    (read: never).  So it gets "likely".
    
    unuse_pde() gets "unlikely" for the same reason.
    
    close_pdeo() gets unlikely as the completion is filled only if there is a
    race between PDE removal and close() (read: never ever).
    
    It even saves code on x86_64 defconfig:
    
            add/remove: 0/0 grow/shrink: 1/2 up/down: 2/-20 (-18)
            Function                                     old     new   delta
            close_pdeo                                   183     185      +2
            proc_reg_get_unmapped_area                   119     111      -8
            proc_reg_poll                                 85      73     -12
    
    Link: http://lkml.kernel.org/r/20180104175657.GA5204@avx2
    Signed-off-by: Alexey Dobriyan <[email protected]>
    Signed-off-by: Andrew Morton <[email protected]>
    Signed-off-by: Linus Torvalds <[email protected]>
---
 fs/proc/inode.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index c5c8e7af5520..6e8724958116 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -129,12 +129,12 @@ enum {BIAS = -1U<<31};
 
 static inline int use_pde(struct proc_dir_entry *pde)
 {
-	return atomic_inc_unless_negative(&pde->in_use);
+	return likely(atomic_inc_unless_negative(&pde->in_use));
 }
 
 static void unuse_pde(struct proc_dir_entry *pde)
 {
-	if (atomic_dec_return(&pde->in_use) == BIAS)
+	if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
 		complete(pde->pde_unload_completion);
 }
 
@@ -167,7 +167,7 @@ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
 		spin_lock(&pde->pde_unload_lock);
 		/* After ->release. */
 		list_del(&pdeo->lh);
-		if (pdeo->c)
+		if (unlikely(pdeo->c))
 			complete(pdeo->c);
 		kfree(pdeo);
 	}
@@ -421,7 +421,7 @@ static const char *proc_get_link(struct dentry *dentry,
 				 struct delayed_call *done)
 {
 	struct proc_dir_entry *pde = PDE(inode);
-	if (unlikely(!use_pde(pde)))
+	if (!use_pde(pde))
 		return ERR_PTR(-EINVAL);
 	set_delayed_call(done, proc_put_link, pde);
 	return pde->data;
--
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