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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-49c603f4d29sm7042380f8f.35.2026.11.13.12.33.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 12:33:14 -0800 (PST) Date: Fri, 13 Nov 2026 20:33:13 +0000 From: David Laight To: Max Kellermann Cc: Alexander Viro , Christian Brauner , Jan Kara , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] fs: pack fields `i_state` and `i_fsnotify_mask` Message-ID: <20261113203313.487a3839@pumpkin> In-Reply-To: <20261113114427.1845888-1-max.kellermann@ionos.com> References: <20261113114427.1845888-1-max.kellermann@ionos.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 13 Nov 2026 12:44:26 +0100 Max Kellermann wrote: I'd use a different workd than 'pack', made me think of __packed. > Both were 32 bit fields followed by a 32 bit hole. This reduces size > of `struct inode` by 8 bytes. > > Moving `i_fsnotify_marks` there as well so they can be in the same > cacheline. > > Signed-off-by: Max Kellermann > --- > v1->v2: move `i_fsnotify_marks` up as well because "should better be > in the same cacheline because these two are accessed on some > performance sensitive paths" (Jan Kara) > --- > include/linux/fs.h | 15 +++++++-------- > 1 file changed, 7 insertions(+), 8 deletions(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 5b3a100aba77..fec047cc3327 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -813,7 +813,13 @@ struct inode { > > /* Misc */ > struct inode_state_flags i_state; > - /* 32-bit hole */ > + > +#ifdef CONFIG_FSNOTIFY > + __u32 i_fsnotify_mask; /* all events this inode cares about */ > + > + struct fsnotify_mark_connector __rcu *i_fsnotify_marks; #else /* 32-bit hole */ ?? David > +#endif > + > struct rw_semaphore i_rwsem; > > /* Timestamp for writeback list ordering and age checks (jiffies). */ > @@ -863,13 +869,6 @@ struct inode { > unsigned i_dir_seq; > }; > > - > -#ifdef CONFIG_FSNOTIFY > - __u32 i_fsnotify_mask; /* all events this inode cares about */ > - /* 32-bit hole reserved for expanding i_fsnotify_mask */ > - struct fsnotify_mark_connector __rcu *i_fsnotify_marks; > -#endif > - > void *i_private; /* fs or device private pointer */ > } __randomize_layout; >