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Commit ac1e69aa authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: don't skip seq_open on write only opens on pidlist files 



Currently, cgroup_pidlist_open() skips seq_open() and pidlist loading
if the file is opened write-only, which is a sensible optimization as
pidlist loading can be costly and there often are occasions where
tasks or cgroup.procs is opened write-only.  However, pidlist init and
release are planned to be moved to cgroup_pidlist_start/stop()
respectively which would make this optimization unnecessary.

This patch removes the optimization and always fully initializes
pidlist files regardless of open mode.  This will help moving pidlist
handling to start/stop by unifying rw paths and removes the need for
specifying cftype->release() in addition to .release in
cgroup_pidlist_operations as file->f_op is now always overridden.  As
pidlist files were the only user of cftype->release(), the next patch
will remove the method.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent c729b11e

kernel/cgroup.c

+1 −12
Original line number Original line Diff line number Diff line
@@ -3781,12 +3781,7 @@ static void cgroup_release_pid_array(struct cgroup_pidlist *l) 
static int cgroup_pidlist_release(struct inode *inode, struct file *file)

static int cgroup_pidlist_release(struct inode *inode, struct file *file)

{

{

	struct cgroup_pidlist *l;

	struct cgroup_pidlist *l;

	if (!(file->f_mode & FMODE_READ))



		return 0;

	/*

	 * the seq_file will only be initialized if the file was opened for

	 * reading; hence we check if it's not null only in that case.

	 */

	l = ((struct seq_file *)file->private_data)->private;

	l = ((struct seq_file *)file->private_data)->private;

	cgroup_release_pid_array(l);

	cgroup_release_pid_array(l);

	return seq_release(inode, file);

	return seq_release(inode, file);
@@ -3811,10 +3806,6 @@ static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type) 
	struct cgroup_pidlist *l;

	struct cgroup_pidlist *l;

	int retval;

	int retval;





	/* Nothing to do for write-only files */

	if (!(file->f_mode & FMODE_READ))

		return 0;



	/* have the array populated */

	/* have the array populated */

	retval = pidlist_array_load(cgrp, type, &l);

	retval = pidlist_array_load(cgrp, type, &l);

	if (retval)

	if (retval)
@@ -3894,7 +3885,6 @@ static struct cftype cgroup_base_files[] = { 
		.name = "cgroup.procs",

		.name = "cgroup.procs",

		.open = cgroup_procs_open,

		.open = cgroup_procs_open,

		.write_u64 = cgroup_procs_write,

		.write_u64 = cgroup_procs_write,

		.release = cgroup_pidlist_release,

		.mode = S_IRUGO | S_IWUSR,

		.mode = S_IRUGO | S_IWUSR,

	},

	},

	{

	{
@@ -3919,7 +3909,6 @@ static struct cftype cgroup_base_files[] = { 
		.flags = CFTYPE_INSANE,		/* use "procs" instead */

		.flags = CFTYPE_INSANE,		/* use "procs" instead */

		.open = cgroup_tasks_open,

		.open = cgroup_tasks_open,

		.write_u64 = cgroup_tasks_write,

		.write_u64 = cgroup_tasks_write,

		.release = cgroup_pidlist_release,

		.mode = S_IRUGO | S_IWUSR,

		.mode = S_IRUGO | S_IWUSR,

	},

	},

	{

	{