From 51ffe41178c49738e4d6d17b9bdcf528a262abc8 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 5 Dec 2013 12:28:02 -0500 Subject: [PATCH] cpuset: convert away from cftype->read() In preparation of conversion to kernfs, cgroup file handling is being consolidated so that it can be easily mapped to the seq_file based interface of kernfs. All users of cftype->read() can be easily served, usually better, by seq_file and other methods. Rename cpuset_common_file_read() to cpuset_common_read_seq_string() and convert it to use read_seq_string() interface instead. This not only simplifies the code but also makes it more versatile. Before, the file couldn't output if the result is longer than PAGE_SIZE. After the conversion, seq_file automatically grows the buffer until the output can fit. This patch doesn't make any visible behavior changes except for being able to handle output larger than PAGE_SIZE. Signed-off-by: Tejun Heo Acked-by: Li Zefan --- kernel/cpuset.c | 71 +++++++++++++++++++-------------------------------------- 1 file changed, 24 insertions(+), 47 deletions(-) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 4772034..032929f 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1731,66 +1731,43 @@ out_unlock: * used, list of ranges of sequential numbers, is variable length, * and since these maps can change value dynamically, one could read * gibberish by doing partial reads while a list was changing. - * A single large read to a buffer that crosses a page boundary is - * ok, because the result being copied to user land is not recomputed - * across a page fault. */ - -static size_t cpuset_sprintf_cpulist(char *page, struct cpuset *cs) -{ - size_t count; - - mutex_lock(&callback_mutex); - count = cpulist_scnprintf(page, PAGE_SIZE, cs->cpus_allowed); - mutex_unlock(&callback_mutex); - - return count; -} - -static size_t cpuset_sprintf_memlist(char *page, struct cpuset *cs) -{ - size_t count; - - mutex_lock(&callback_mutex); - count = nodelist_scnprintf(page, PAGE_SIZE, cs->mems_allowed); - mutex_unlock(&callback_mutex); - - return count; -} - -static ssize_t cpuset_common_file_read(struct cgroup_subsys_state *css, - struct cftype *cft, struct file *file, - char __user *buf, size_t nbytes, - loff_t *ppos) +static int cpuset_common_read_seq_string(struct cgroup_subsys_state *css, + struct cftype *cft, + struct seq_file *sf) { struct cpuset *cs = css_cs(css); cpuset_filetype_t type = cft->private; - char *page; - ssize_t retval = 0; - char *s; + ssize_t count; + char *buf, *s; + int ret = 0; - if (!(page = (char *)__get_free_page(GFP_TEMPORARY))) - return -ENOMEM; + count = seq_get_buf(sf, &buf); + s = buf; - s = page; + mutex_lock(&callback_mutex); switch (type) { case FILE_CPULIST: - s += cpuset_sprintf_cpulist(s, cs); + s += cpulist_scnprintf(s, count, cs->cpus_allowed); break; case FILE_MEMLIST: - s += cpuset_sprintf_memlist(s, cs); + s += nodelist_scnprintf(s, count, cs->mems_allowed); break; default: - retval = -EINVAL; - goto out; + ret = -EINVAL; + goto out_unlock; } - *s++ = '\n'; - retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page); -out: - free_page((unsigned long)page); - return retval; + if (s < buf + count - 1) { + *s++ = '\n'; + seq_commit(sf, s - buf); + } else { + seq_commit(sf, -1); + } +out_unlock: + mutex_unlock(&callback_mutex); + return ret; } static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) @@ -1847,7 +1824,7 @@ static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) static struct cftype files[] = { { .name = "cpus", - .read = cpuset_common_file_read, + .read_seq_string = cpuset_common_read_seq_string, .write_string = cpuset_write_resmask, .max_write_len = (100U + 6 * NR_CPUS), .private = FILE_CPULIST, @@ -1855,7 +1832,7 @@ static struct cftype files[] = { { .name = "mems", - .read = cpuset_common_file_read, + .read_seq_string = cpuset_common_read_seq_string, .write_string = cpuset_write_resmask, .max_write_len = (100U + 6 * MAX_NUMNODES), .private = FILE_MEMLIST, -- 2.7.4