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[5.186.114.212]) by smtp.gmail.com with ESMTPSA id a11-v6sm2739032edn.95.2018.08.18.06.24.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Sat, 18 Aug 2018 06:24:42 -0700 (PDT) From: Rasmus Villemoes To: Jonathan Corbet , Alexander Viro Cc: linux-kernel@vger.kernel.org, Rasmus Villemoes , Andreas Dilger , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, Alexey Dobriyan , linux-nfs@vger.kernel.org, cluster-devel@redhat.com, Michael Ellerman , linuxppc-dev@lists.ozlabs.org, Thierry Reding , Lorenzo Pieralisi Subject: [PATCH v2 1/8] seq_file: introduce seq_open_data helper Date: Sat, 18 Aug 2018 15:24:27 +0200 Message-Id: <20180818132434.9515-1-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.16.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- v2: - Fix some copy-pastos spotted by Andreas. - Ensure everybody hit by an example patch also gets this cover letter/introducing patch. - Include a few fs/ examples. I've just included a few examples of possible users of this helper, there are many more similar cases. As a bonus, 7/8 fix a potential NULL deref (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 | 16 ++++++++++++---- include/linux/seq_file.h | 1 + 3 files changed, 18 insertions(+), 8 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 4cc090b50cc5..c8c86660f6db 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -33,11 +33,12 @@ static void *seq_buf_alloc(unsigned long size) } /** - * seq_open - initialize sequential file + * seq_open_data - initialize sequential file * @file: file we initialize * @op: method table describing the sequence + * @data: initial value for ->private field * - * seq_open() sets @file, associating it with a sequence described + * seq_open_data() sets @file, associating it with a sequence described * by @op. @op->start() sets the iterator up and returns the first * element of sequence. @op->stop() shuts it down. @op->next() * returns the next element of sequence. @op->show() prints element @@ -45,10 +46,10 @@ static void *seq_buf_alloc(unsigned long size) * ERR_PTR(error). In the end of sequence they return %NULL. ->show() * returns 0 in case of success and negative number in case of error. * Returning SEQ_SKIP means "discard this element and move on". - * Note: seq_open() will allocate a struct seq_file and store its + * Note: seq_open_data() 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; @@ -62,6 +63,7 @@ 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. @@ -86,6 +88,12 @@ int seq_open(struct file *file, const struct seq_operations *op) file->f_mode &= ~FMODE_PWRITE; return 0; } +EXPORT_SYMBOL(seq_open_data); + +int seq_open(struct file *file, const struct seq_operations *op) +{ + return seq_open_data(file, op, NULL); +} EXPORT_SYMBOL(seq_open); static int traverse(struct seq_file *m, loff_t offset) diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h index a121982af0f5..1142e39bfad2 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 *); -- 2.16.4