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[71.40.0.58]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-3e852058dcesm486754fac.9.2025.11.12.17.36.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Nov 2025 17:36:38 -0800 (PST) From: jayxu1990@gmail.com To: viro@zeniv.linux.org.uk, brauner@kernel.org Cc: jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, jayxu1990@gmail.com, rdlee.upstream@gmail.com, avnerkhan@utexas.edu Subject: [PATCH] fs: optimize chown_common by skipping unnecessary ownership changes Date: Thu, 13 Nov 2025 09:34:49 +0800 Message-Id: <20251113013449.3874650-1-jayxu1990@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jay Xu Add early return optimization to chown_common() when the requested uid/gid already matches the current inode ownership. This avoids calling notify_change() and associated filesystem operations when no actual change is needed. The check is performed after acquiring the inode lock to ensure atomicity and uses the kernel's uid_eq()/gid_eq() functions for proper comparison. This optimization provides several benefits: - Reduces unnecessary filesystem metadata updates and journal writes - Prevents redundant storage I/O when files are on persistent storage - Improves performance for recursive chown operations that encounter files with already-correct ownership - Avoids invoking security hooks and filesystem-specific setattr operations when no change is required Signed-off-by: Jay Xu --- fs/open.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/open.c b/fs/open.c index 3d64372ecc67..82bde70c6c08 100644 --- a/fs/open.c +++ b/fs/open.c @@ -761,6 +761,7 @@ int chown_common(const struct path *path, uid_t user, g= id_t group) struct iattr newattrs; kuid_t uid; kgid_t gid; + bool needs_update =3D false; =20 uid =3D make_kuid(current_user_ns(), user); gid =3D make_kgid(current_user_ns(), group); @@ -779,6 +780,17 @@ int chown_common(const struct path *path, uid_t user, = gid_t group) error =3D inode_lock_killable(inode); if (error) return error; + + /* Check if ownership actually needs to change */ + if ((newattrs.ia_valid & ATTR_UID) && !uid_eq(inode->i_uid, uid)) + needs_update =3D true; + if ((newattrs.ia_valid & ATTR_GID) && !gid_eq(inode->i_gid, gid)) + needs_update =3D true; + + if (!needs_update) { + inode_unlock(inode); + return 0; + } if (!S_ISDIR(inode->i_mode)) newattrs.ia_valid |=3D ATTR_KILL_SUID | ATTR_KILL_PRIV | setattr_should_drop_sgid(idmap, inode); --=20 2.34.1