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[118.238.203.205]) by smtp.gmail.com with ESMTPSA id l63-v6sm46356677pfb.75.2018.11.20.18.44.30 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 20 Nov 2018 18:44:34 -0800 (PST) From: Eiichi Tsukata To: andi@firstfloor.org, Chris Mason , Josef Bacik , David Sterba , "Theodore Ts'o" , Andreas Dilger , Jaegeuk Kim , Chao Yu , Miklos Szeredi , Bob Peterson , Andreas Gruenbacher , Alexander Viro , linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, cluster-devel@redhat.com, linux-unionfs@vger.kernel.org Cc: Eiichi Tsukata Subject: [PATCH v1 4/4] overlayfs: fix race between llseek SEEK_END and write Date: Wed, 21 Nov 2018 11:44:00 +0900 Message-Id: <20181121024400.4346-5-devel@etsukata.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181121024400.4346-1-devel@etsukata.com> References: <20181121024400.4346-1-devel@etsukata.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Implement individual lock for SEEK_END for overlayfs which directly calls generic_file_llseek_size(). Signed-off-by: Eiichi Tsukata --- fs/overlayfs/file.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index 84dd957efa24..57bc6538eea8 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -146,10 +146,27 @@ static int ovl_release(struct inode *inode, struct file *file) static loff_t ovl_llseek(struct file *file, loff_t offset, int whence) { struct inode *realinode = ovl_inode_real(file_inode(file)); + loff_t ret; - return generic_file_llseek_size(file, offset, whence, - realinode->i_sb->s_maxbytes, - i_size_read(realinode)); + switch (whence) { + default: + return generic_file_llseek_size(file, offset, whence, + realinode->i_sb->s_maxbytes, + i_size_read(realinode)); + case SEEK_END: + case SEEK_DATA: + case SEEK_HOLE: + /* + * protects against inode size race with write so that llseek + * doesn't see inode size being updated in individual fs write + */ + inode_lock(realinode); + ret = generic_file_llseek_size(file, offset, whence, + realinode->i_sb->s_maxbytes, + i_size_read(realinode)); + inode_unlock(realinode); + return ret; + } } static void ovl_file_accessed(struct file *file) -- 2.19.1