[PATCH v3 3/8] proc/kcore: replace kclist_lock rwlock with rwsem

[Omar Sandoval]

From: Omar Sandoval <osan...@fb.com>

Now we only need kclist_lock from user context and at fs init time, and
the following changes need to sleep while holding the kclist_lock.

Signed-off-by: Omar Sandoval <osan...@fb.com>
---
 fs/proc/kcore.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index e83f15a4f66d..ae43a97d511d 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -59,7 +59,7 @@ struct memelfnote
 };
 
 static LIST_HEAD(kclist_head);
-static DEFINE_RWLOCK(kclist_lock);
+static DECLARE_RWSEM(kclist_lock);
 static int kcore_need_update = 1;
 
 /* This doesn't grab kclist_lock, so it should only be used at init time. */
@@ -117,7 +117,7 @@ static void __kcore_update_ram(struct list_head *list)
        struct kcore_list *tmp, *pos;
        LIST_HEAD(garbage);
 
-       write_lock(&kclist_lock);
+       down_write(&kclist_lock);
        if (xchg(&kcore_need_update, 0)) {
                list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
                        if (pos->type == KCORE_RAM
@@ -128,7 +128,7 @@ static void __kcore_update_ram(struct list_head *list)
        } else
                list_splice(list, &garbage);
        proc_root_kcore->size = get_kcore_size(&nphdr, &size);
-       write_unlock(&kclist_lock);
+       up_write(&kclist_lock);
 
        free_kclist_ents(&garbage);
 }
@@ -451,11 +451,11 @@ read_kcore(struct file *file, char __user *buffer, size_t 
buflen, loff_t *fpos)
        int nphdr;
        unsigned long start;
 
-       read_lock(&kclist_lock);
+       down_read(&kclist_lock);
        size = get_kcore_size(&nphdr, &elf_buflen);
 
        if (buflen == 0 || *fpos >= size) {
-               read_unlock(&kclist_lock);
+               up_read(&kclist_lock);
                return 0;
        }
 
@@ -472,11 +472,11 @@ read_kcore(struct file *file, char __user *buffer, size_t 
buflen, loff_t *fpos)
                        tsz = buflen;
                elf_buf = kzalloc(elf_buflen, GFP_ATOMIC);
                if (!elf_buf) {
-                       read_unlock(&kclist_lock);
+                       up_read(&kclist_lock);
                        return -ENOMEM;
                }
                elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);
-               read_unlock(&kclist_lock);
+               up_read(&kclist_lock);
                if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
                        kfree(elf_buf);
                        return -EFAULT;
@@ -491,7 +491,7 @@ read_kcore(struct file *file, char __user *buffer, size_t 
buflen, loff_t *fpos)
                if (buflen == 0)
                        return acc;
        } else
-               read_unlock(&kclist_lock);
+               up_read(&kclist_lock);
 
        /*
         * Check to see if our file offset matches with any of
@@ -504,12 +504,12 @@ read_kcore(struct file *file, char __user *buffer, size_t 
buflen, loff_t *fpos)
        while (buflen) {
                struct kcore_list *m;
 
-               read_lock(&kclist_lock);
+               down_read(&kclist_lock);
                list_for_each_entry(m, &kclist_head, list) {
                        if (start >= m->addr && start < (m->addr+m->size))
                                break;
                }
-               read_unlock(&kclist_lock);
+               up_read(&kclist_lock);
 
                if (&m->list == &kclist_head) {
                        if (clear_user(buffer, tsz))
-- 
2.18.0