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

This reverts commit 5ffd3412ae
("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
This commit is contained in:
Thomas Betker 2015-11-10 22:18:15 +01:00 committed by David Woodhouse
parent 38714fbd29
commit 157078f64b
1 changed files with 19 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
fs/jffs2/file.c
View File

@ -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;
pg = grab_cache_page_write_begin(mapping, index, flags);
if (!pg)
return -ENOMEM;
*pagep = pg;
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);
return -ENOMEM;
}
*pagep = pg;
if (alloc_len) {
/* 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;
}