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Subject[PATCH] ufs: fix deadlocks after mutex merge
Date
Commit 0244756edc4b ("ufs: sb mutex merge + mutex_destroy") introduces
deadlocks in ufs_new_inode() and ufs_free_inode() that call lock_ufs()
being already invoked with mutex held.

ufs_free_inode() is always invoked with mutex locked, while
ufs_new_inode() is called with mutex locked two times of four.

The patch proposes to resolve the issue by agreement to call
ufs_new_inode() and ufs_free_inode() with mutex unheld.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
fs/ufs/inode.c | 7 ++-----
fs/ufs/namei.c | 14 ++++++--------
2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/fs/ufs/inode.c b/fs/ufs/inode.c
index 7c580c97990e..be7d42c7d938 100644
--- a/fs/ufs/inode.c
+++ b/fs/ufs/inode.c
@@ -902,9 +902,6 @@ void ufs_evict_inode(struct inode * inode)
invalidate_inode_buffers(inode);
clear_inode(inode);

- if (want_delete) {
- lock_ufs(inode->i_sb);
- ufs_free_inode (inode);
- unlock_ufs(inode->i_sb);
- }
+ if (want_delete)
+ ufs_free_inode(inode);
}
diff --git a/fs/ufs/namei.c b/fs/ufs/namei.c
index 90d74b8f8eba..2df62a73f20c 100644
--- a/fs/ufs/namei.c
+++ b/fs/ufs/namei.c
@@ -126,12 +126,12 @@ static int ufs_symlink (struct inode * dir, struct dentry * dentry,
if (l > sb->s_blocksize)
goto out_notlocked;

- lock_ufs(dir->i_sb);
inode = ufs_new_inode(dir, S_IFLNK | S_IRWXUGO);
err = PTR_ERR(inode);
if (IS_ERR(inode))
- goto out;
+ goto out_notlocked;

+ lock_ufs(dir->i_sb);
if (l > UFS_SB(sb)->s_uspi->s_maxsymlinklen) {
/* slow symlink */
inode->i_op = &ufs_symlink_inode_operations;
@@ -181,13 +181,9 @@ static int ufs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
struct inode * inode;
int err;

- lock_ufs(dir->i_sb);
- inode_inc_link_count(dir);
-
inode = ufs_new_inode(dir, S_IFDIR|mode);
- err = PTR_ERR(inode);
if (IS_ERR(inode))
- goto out_dir;
+ return PTR_ERR(inode);

inode->i_op = &ufs_dir_inode_operations;
inode->i_fop = &ufs_dir_operations;
@@ -195,6 +191,9 @@ static int ufs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)

inode_inc_link_count(inode);

+ lock_ufs(dir->i_sb);
+ inode_inc_link_count(dir);
+
err = ufs_make_empty(inode, dir);
if (err)
goto out_fail;
@@ -212,7 +211,6 @@ out_fail:
inode_dec_link_count(inode);
inode_dec_link_count(inode);
iput (inode);
-out_dir:
inode_dec_link_count(dir);
unlock_ufs(dir->i_sb);
goto out;
--
1.9.1


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