Revert "jffs2: Fix lock acquisition order bug in jffs2_write_begin"

This reverts commit 5ffd3412ae55
("jffs2: Fix lock acquisition order bug in jffs2_write_begin").

The commit modified jffs2_write_begin() to remove a deadlock with
jffs2_garbage_collect_live(), but this introduced new deadlocks found
by multiple users. page_lock() actually has to be called before
mutex_lock(&c->alloc_sem) or mutex_lock(&f->sem) because
jffs2_write_end() and jffs2_readpage() are called with the page locked,
and they acquire c->alloc_sem and f->sem, resp.

In other words, the lock order in jffs2_write_begin() was correct, and
it is the jffs2_garbage_collect_live() path that has to be changed.

Revert the commit to get rid of the new deadlocks, and to clear the way
for a better fix of the original deadlock.

Reported-by: Deng Chao <deng.chao1@zte.com.cn>
Reported-by: Ming Liu <liu.ming50@gmail.com>
Reported-by: wangzaiwei <wangzaiwei@top-vision.cn>
Signed-off-by: Thomas Betker <thomas.betker@rohde-schwarz.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Cc: stable@vger.kernel.org

1 files changed, 18 insertions, 21 deletions

diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c
index c5ac5944bc1b..cad86bac3453 100644
--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -137,39 +137,33 @@ static int jffs2_write_begin(struct file *filp, struct address_space *mapping,
         struct page *pg;
         struct inode *inode = mapping->host;
         struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode);
-        struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb);
-        struct jffs2_raw_inode ri;
-        uint32_t alloc_len = 0;
         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
         uint32_t pageofs = index << PAGE_CACHE_SHIFT;
         int ret = 0;
 
-        jffs2_dbg(1, "%s()\n", __func__);
-
-        if (pageofs > inode->i_size) {
-                ret = jffs2_reserve_space(c, sizeof(ri), &alloc_len,
-                                          ALLOC_NORMAL, JFFS2_SUMMARY_INODE_SIZE);
-                if (ret)
-                        return ret;
-        }
-
-        mutex_lock(&f->sem);
         pg = grab_cache_page_write_begin(mapping, index, flags);
-        if (!pg) {
-                if (alloc_len)
-                        jffs2_complete_reservation(c);
-                mutex_unlock(&f->sem);
+        if (!pg)
                 return -ENOMEM;
-        }
         *pagep = pg;
 
-        if (alloc_len) {
+        jffs2_dbg(1, "%s()\n", __func__);
+
+        if (pageofs > inode->i_size) {
                 /* Make new hole frag from old EOF to new page */
+                struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb);
+                struct jffs2_raw_inode ri;
                 struct jffs2_full_dnode *fn;
+                uint32_t alloc_len;
 
                 jffs2_dbg(1, "Writing new hole frag 0x%x-0x%x between current EOF and new page\n",
                           (unsigned int)inode->i_size, pageofs);
 
+                ret = jffs2_reserve_space(c, sizeof(ri), &alloc_len,
+                                          ALLOC_NORMAL, JFFS2_SUMMARY_INODE_SIZE);
+                if (ret)
+                        goto out_page;
+
+                mutex_lock(&f->sem);
                 memset(&ri, 0, sizeof(ri));
 
                 ri.magic = cpu_to_je16(JFFS2_MAGIC_BITMASK);
@@ -196,6 +190,7 @@ static int jffs2_write_begin(struct file *filp, struct address_space *mapping,
                 if (IS_ERR(fn)) {
                         ret = PTR_ERR(fn);
                         jffs2_complete_reservation(c);
+                        mutex_unlock(&f->sem);
                         goto out_page;
                 }
                 ret = jffs2_add_full_dnode_to_inode(c, f, fn);
@@ -210,10 +205,12 @@ static int jffs2_write_begin(struct file *filp, struct address_space *mapping,
                         jffs2_mark_node_obsolete(c, fn->raw);
                         jffs2_free_full_dnode(fn);
                         jffs2_complete_reservation(c);
+                        mutex_unlock(&f->sem);
                         goto out_page;
                 }
                 jffs2_complete_reservation(c);
                 inode->i_size = pageofs;
+                mutex_unlock(&f->sem);
         }
 
         /*
@@ -222,18 +219,18 @@ static int jffs2_write_begin(struct file *filp, struct address_space *mapping,
          * case of a short-copy.
          */
         if (!PageUptodate(pg)) {
+                mutex_lock(&f->sem);
                 ret = jffs2_do_readpage_nolock(inode, pg);
+                mutex_unlock(&f->sem);
                 if (ret)
                         goto out_page;
         }
-        mutex_unlock(&f->sem);
         jffs2_dbg(1, "end write_begin(). pg->flags %lx\n", pg->flags);
         return ret;
 
 out_page:
         unlock_page(pg);
         page_cache_release(pg);
-        mutex_unlock(&f->sem);
         return ret;
 }