This is a note to let you know that I've just added the patch titled

binder: fix log spam for existing debugfs file creation.

to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

From eb143f8756e77c8fcfc4d574922ae9efd3a43ca9 Mon Sep 17 00:00:00 2001

From: Martin Fuzzey martin.fuzzey@flowbird.group Date: Fri, 10 Jan 2020 16:44:01 +0100 Subject: binder: fix log spam for existing debugfs file creation.

Since commit 43e23b6c0b01 ("debugfs: log errors when something goes wrong") debugfs logs attempts to create existing files.

However binder attempts to create multiple debugfs files with the same name when a single PID has multiple contexts, this leads to log spamming during an Android boot (17 such messages during boot on my system).

Fix this by checking if we already know the PID and only create the debugfs entry for the first context per PID.

Do the same thing for binderfs for symmetry.

Signed-off-by: Martin Fuzzey martin.fuzzey@flowbird.group Acked-by: Todd Kjos tkjos@google.com Fixes: 43e23b6c0b01 ("debugfs: log errors when something goes wrong") Cc: stable stable@vger.kernel.org Link: https://lore.kernel.org/r/1578671054-5982-1-git-send-email-martin.fuzzey@flo... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/android/binder.c | 37 +++++++++++++++++++------------------ 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c index b2dad43dbf82..9fcc761031d8 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -5199,10 +5199,11 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)

static int binder_open(struct inode *nodp, struct file *filp) { - struct binder_proc *proc; + struct binder_proc *proc, *itr; struct binder_device *binder_dev; struct binderfs_info *info; struct dentry *binder_binderfs_dir_entry_proc = NULL; + bool existing_pid = false;

binder_debug(BINDER_DEBUG_OPEN_CLOSE, "%s: %d:%d\n", __func__, current->group_leader->pid, current->pid); @@ -5235,19 +5236,24 @@ static int binder_open(struct inode *nodp, struct file *filp) filp->private_data = proc;

mutex_lock(&binder_procs_lock); + hlist_for_each_entry(itr, &binder_procs, proc_node) { + if (itr->pid == proc->pid) { + existing_pid = true; + break; + } + } hlist_add_head(&proc->proc_node, &binder_procs); mutex_unlock(&binder_procs_lock);

- if (binder_debugfs_dir_entry_proc) { + if (binder_debugfs_dir_entry_proc && !existing_pid) { char strbuf[11];

snprintf(strbuf, sizeof(strbuf), "%u", proc->pid); /* - * proc debug entries are shared between contexts, so - * this will fail if the process tries to open the driver - * again with a different context. The priting code will - * anyway print all contexts that a given PID has, so this - * is not a problem. + * proc debug entries are shared between contexts. + * Only create for the first PID to avoid debugfs log spamming + * The printing code will anyway print all contexts for a given + * PID so this is not a problem. */ proc->debugfs_entry = debugfs_create_file(strbuf, 0444, binder_debugfs_dir_entry_proc, @@ -5255,19 +5261,16 @@ static int binder_open(struct inode *nodp, struct file *filp) &proc_fops); }

- if (binder_binderfs_dir_entry_proc) { + if (binder_binderfs_dir_entry_proc && !existing_pid) { char strbuf[11]; struct dentry *binderfs_entry;

snprintf(strbuf, sizeof(strbuf), "%u", proc->pid); /* * Similar to debugfs, the process specific log file is shared - * between contexts. If the file has already been created for a - * process, the following binderfs_create_file() call will - * fail with error code EEXIST if another context of the same - * process invoked binder_open(). This is ok since same as - * debugfs, the log file will contain information on all - * contexts of a given PID. + * between contexts. Only create for the first PID. + * This is ok since same as debugfs, the log file will contain + * information on all contexts of a given PID. */ binderfs_entry = binderfs_create_file(binder_binderfs_dir_entry_proc, strbuf, &proc_fops, (void *)(unsigned long)proc->pid); @@ -5277,10 +5280,8 @@ static int binder_open(struct inode *nodp, struct file *filp) int error;

error = PTR_ERR(binderfs_entry); - if (error != -EEXIST) { - pr_warn("Unable to create file %s in binderfs (error %d)\n", - strbuf, error); - } + pr_warn("Unable to create file %s in binderfs (error %d)\n", + strbuf, error); } }