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c=relaxed/simple; d=kernel.org; s=k20201202; t=1690531620; bh=SA6A0yrELgyo+eU0lbBKfgUSEb8O2y86fT7korpoL+s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bKjSac6+s1O1BFRDRt3KJXlNfmtkeUFgxzL9bivmAOZYlD56X7PApiT3jiFLSA+sf 95iXJ0TOzO40qcC9gk1/fUuyDhjxl6Se+JFYaT86iEwUnZxvPHrMZkOYQOLPwWI+NP F0LWIyto9CBoVtwHZ4rk7dzVhVtg9M7Fz+2Vi0qy3Dwf3SFhLM06cLY3dezQJBfIkP q7OC41NAUTSnYK3FnOe8JuvzPeDHGecv7acPyHv5SzJe59+oa+wYYI14MK/LLesRPD Y4XWYGdtVP2/E4A645ddzEuC3S0J40qF3jx/+GzOxAeEJ7W2pBZ7sXh0SrZJpSoPQZ wS6E25n0WwXPA== From: Christian Brauner To: Chuck Lever , oliver.sang@intel.com Cc: Christian Brauner , Chuck Lever , oe-lkp@lists.linux.dev, ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH RFC] libfs: Remove parent dentry locking in offset_iterate_dir() Date: Fri, 28 Jul 2023 10:06:49 +0200 Message-Id: <20230728-sorglos-krempel-7f7b18c4c247@brauner> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169030957098.157536.9938425508695693348.stgit@manet.1015granger.net> References: <169030957098.157536.9938425508695693348.stgit@manet.1015granger.net> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Developer-Signature: v=1; a=openpgp-sha256; l=1353; i=brauner@kernel.org; h=from:subject:message-id; bh=SA6A0yrELgyo+eU0lbBKfgUSEb8O2y86fT7korpoL+s=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMaQcLhefcL/u7cnS23MzZCTuNJ6VOifrzPiA7TCDr8wSrlsW N7/UdJSyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAExkuSfDfzeVyGoH2R1vNgWuaf+9Ji tiygMr16IzFcY1CTfm/on7Lc7I8Htb6KWyKaqHH/WuzGxyTNB8wZjnNaOFa+/fjF/CbxiSWAE= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 1AF2640007 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ddwhqay6sbp8dr64z1zdmcjdg3cdgu4q X-HE-Tag: 1690531621-682495 X-HE-Meta: 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 274uwauH 7oiVpqlTpMraeWrKXNpERFBojwFFUX12GmpIic/9aHCSMBs3Lo1nmX7JlVe+zZtW1VLsww+3HUHtoQy44z1EtuuNPHR9iK2VjlDrD5G/2zCG/MhvwZAXtKKiuA96QUxxj/IS+ImZMOMQ+h+pllOTGdpGFuQY0ANftwUp/YM+K+Sq5LI18NylSaL4hliCy6Nmg3dBbjCeYtkWDFedjIA3yB+A33GH7yp3v3bS04KyRG9aYwe7TYbfg3tcZOerkputJtMbz3Hv8CgItlU9lxVjgVBSiaBeEvTtzmoYdBcGK1en3zFDfJKIESvWdKOcjUfZfgOersoxKID/8cYgd9n0tjngeIC/rCAJ80YOjSEDBE9Yu2XlSz5oD6b3GMPesK37CjlSvPtVOMSZv92Y= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 25 Jul 2023 14:31:04 -0400, Chuck Lever wrote: > Since offset_iterate_dir() does not walk the parent's d_subdir list > nor does it manipulate the parent's d_child, there doesn't seem to > be a reason to hold the parent's d_lock. The offset_ctx's xarray can > be sufficiently protected with just the RCU read lock. > > Flame graph data captured during the git regression run shows a > 20% reduction in CPU cycles consumed in offset_find_next(). > > [...] I've picked this up. It would be very nice if we could get a perf test from lkp for this fix. --- Applied to the vfs.tmpfs branch of the vfs/vfs.git tree. Patches in the vfs.tmpfs branch should appear in linux-next soon. Please report any outstanding bugs that were missed during review in a new review to the original patch series allowing us to drop it. It's encouraged to provide Acked-bys and Reviewed-bys even though the patch has now been applied. If possible patch trailers will be updated. Note that commit hashes shown below are subject to change due to rebase, trailer updates or similar. If in doubt, please check the listed branch. tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git branch: vfs.tmpfs [1/1] libfs: Remove parent dentry locking in offset_iterate_dir() https://git.kernel.org/vfs/vfs/c/01c45fd0472c