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authorThomas Betker <thomas.betker@freenet.de>2012-10-17 22:59:30 +0200
committerArtem Bityutskiy <artem.bityutskiy@linux.intel.com>2012-11-09 17:02:50 +0200
commit5ffd3412ae5536a4c57469cb8ea31887121dcb2e (patch)
tree33c9d89eabf70c49e683a36be800be3b4582a358 /fs/jffs2
parent0131950ebd146b5e31508233352d6f4625af25b1 (diff)
downloadlinux-5ffd3412ae5536a4c57469cb8ea31887121dcb2e.tar.gz
jffs2: Fix lock acquisition order bug in jffs2_write_begin
jffs2_write_begin() first acquires the page lock, then f->sem. This causes an AB-BA deadlock with jffs2_garbage_collect_live(), which first acquires f->sem, then the page lock: jffs2_garbage_collect_live mutex_lock(&f->sem) (A) jffs2_garbage_collect_dnode jffs2_gc_fetch_page read_cache_page_async do_read_cache_page lock_page(page) (B) jffs2_write_begin grab_cache_page_write_begin find_lock_page lock_page(page) (B) mutex_lock(&f->sem) (A) We fix this by restructuring jffs2_write_begin() to take f->sem before the page lock. However, we make sure that f->sem is not held when calling jffs2_reserve_space(), as this is not permitted by the locking rules. The deadlock above was observed multiple times on an SoC with a dual ARMv7 (Cortex-A9), running the long-term 3.4.11 kernel; it occurred when using scp to copy files from a host system to the ARM target system. The fix was heavily tested on the same target system. Cc: stable@vger.kernel.org Signed-off-by: Thomas Betker <thomas.betker@rohde-schwarz.com> Acked-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Diffstat (limited to 'fs/jffs2')
-rw-r--r--fs/jffs2/file.c39
1 files changed, 21 insertions, 18 deletions
diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c
index 60ef3fb707f..1506673c087 100644
--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -138,33 +138,39 @@ 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 (!pg) {
+ if (alloc_len)
+ jffs2_complete_reservation(c);
+ mutex_unlock(&f->sem);
return -ENOMEM;
+ }
*pagep = pg;
- jffs2_dbg(1, "%s()\n", __func__);
-
- if (pageofs > inode->i_size) {
+ 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);
@@ -191,7 +197,6 @@ 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);
@@ -206,12 +211,10 @@ 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);
}
/*
@@ -220,18 +223,18 @@ 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;
}