From 5370b43e4bcf60049bfd44db83ba8d2ec43d0152 Mon Sep 17 00:00:00 2001 From: Mateusz Guzik Date: Wed, 19 Mar 2025 22:58:01 +0100 Subject: fs: reduce work in fdget_pos() 1. predict the file was found 2. explicitly compare the ref to "one", ignoring the dead zone The latter arguably improves the behavior to begin with. Suppose the count turned bad -- the previously used ref routine is going to check for it and return 0, indicating the count does not necessitate taking ->f_pos_lock. But there very well may be several users. i.e. not paying for special-casing the dead zone improves semantics. While here spell out each condition in a dedicated if statement. This has no effect on generated code. Sizes are as follows (in bytes; gcc 13, x86-64): stock: 321 likely(): 298 likely()+ref: 280 Signed-off-by: Mateusz Guzik Link: https://lore.kernel.org/r/20250319215801.1870660-1-mjguzik@gmail.com Signed-off-by: Christian Brauner --- include/linux/file_ref.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include/linux') diff --git a/include/linux/file_ref.h b/include/linux/file_ref.h index 6ef92d765a66..7db62fbc0500 100644 --- a/include/linux/file_ref.h +++ b/include/linux/file_ref.h @@ -208,4 +208,18 @@ static inline unsigned long file_ref_read(file_ref_t *ref) return c >= FILE_REF_RELEASED ? 0 : c + 1; } +/* + * __file_ref_read_raw - Return the value stored in ref->refcnt + * @ref: Pointer to the reference count + * + * Return: The raw value found in the counter + * + * A hack for file_needs_f_pos_lock(), you probably want to use + * file_ref_read() instead. + */ +static inline unsigned long __file_ref_read_raw(file_ref_t *ref) +{ + return atomic_long_read(&ref->refcnt); +} + #endif -- cgit v1.2.3