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[5.186.126.104]) by smtp.gmail.com with ESMTPSA id e12sm4088274edi.29.2018.03.01.15.37.29 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 01 Mar 2018 15:37:30 -0800 (PST) From: Rasmus Villemoes To: Jonathan Corbet , Alexander Viro Cc: Rasmus Villemoes , Tony Luck , linux-ia64@vger.kernel.org, Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [RFC 1/5] seq_file: introduce seq_open_data helper Date: Fri, 2 Mar 2018 00:37:20 +0100 Message-Id: <20180301233724.20440-1-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.15.1 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP There are quite a few callers of seq_open that could be simplified by setting the ->private member via the seq_open call instead of fetching file->private_data afterwards. Signed-off-by: Rasmus Villemoes --- I've just included a few examples of possible users of this helper, there are many more similar cases. As a bonus, the first two fix potential NULL derefs (if one believes that seq_open can actually fail). seq_open_private would have been a better name, but that one is already taken... Documentation/filesystems/seq_file.txt | 9 +++++---- fs/seq_file.c | 9 ++++++++- include/linux/seq_file.h | 1 + 3 files changed, 14 insertions(+), 5 deletions(-) diff --git a/Documentation/filesystems/seq_file.txt b/Documentation/filesystems/seq_file.txt index 9de4303201e1..68571b8275d8 100644 --- a/Documentation/filesystems/seq_file.txt +++ b/Documentation/filesystems/seq_file.txt @@ -234,10 +234,11 @@ Here, the call to seq_open() takes the seq_operations structure we created before, and gets set up to iterate through the virtual file. On a successful open, seq_open() stores the struct seq_file pointer in -file->private_data. If you have an application where the same iterator can -be used for more than one file, you can store an arbitrary pointer in the -private field of the seq_file structure; that value can then be retrieved -by the iterator functions. +file->private_data. If you have an application where the same iterator +can be used for more than one file, you can store an arbitrary pointer +in the private field of the seq_file structure; that value can then be +retrieved by the iterator functions. Using the wrapper seq_open_data() +allows you to set the initial value for that field. There is also a wrapper function to seq_open() called seq_open_private(). It kmallocs a zero filled block of memory and stores a pointer to it in the diff --git a/fs/seq_file.c b/fs/seq_file.c index eea09f6d8830..f2145cb6e23d 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -45,7 +45,7 @@ static void *seq_buf_alloc(unsigned long size) * Note: seq_open() will allocate a struct seq_file and store its * pointer in @file->private_data. This pointer should not be modified. */ -int seq_open(struct file *file, const struct seq_operations *op) +int seq_open_data(struct file *file, const struct seq_operations *op, void *data) { struct seq_file *p; @@ -59,6 +59,7 @@ int seq_open(struct file *file, const struct seq_operations *op) mutex_init(&p->lock); p->op = op; + p->private = data; // No refcounting: the lifetime of 'p' is constrained // to the lifetime of the file. @@ -85,6 +86,12 @@ int seq_open(struct file *file, const struct seq_operations *op) } EXPORT_SYMBOL(seq_open); +int seq_open(struct file *file, const struct seq_operations *op) +{ + return seq_open_data(file, op, NULL); +} +EXPORT_SYMBOL(seq_open_data); + static int traverse(struct seq_file *m, loff_t offset) { loff_t pos = 0, index; diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h index ab437dd2e3b9..f5ff376fa62b 100644 --- a/include/linux/seq_file.h +++ b/include/linux/seq_file.h @@ -107,6 +107,7 @@ void seq_pad(struct seq_file *m, char c); char *mangle_path(char *s, const char *p, const char *esc); int seq_open(struct file *, const struct seq_operations *); +int seq_open_data(struct file *, const struct seq_operations *, void *); ssize_t seq_read(struct file *, char __user *, size_t, loff_t *); loff_t seq_lseek(struct file *, loff_t, int); int seq_release(struct inode *, struct file *);