GitHub-Mirror/Star64_linux
2
0
Fork 0
mirror of https://github.com/Fishwaldo/Star64_linux.git synced 2025-03-15 11:44:11 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

fs: Establish locking order for unrelated directories

Browse source 
commit f23ce75718 upstream.

Currently the locking order of inode locks for directories that are not
in ancestor relationship is not defined because all operations that
needed to lock two directories like this were serialized by
sb->s_vfs_rename_mutex. However some filesystems need to lock two
subdirectories for RENAME_EXCHANGE operations and for this we need the
locking order established even for two tree-unrelated directories.
Provide a helper function lock_two_inodes() that establishes lock
ordering for any two inodes and use it in lock_two_directories().

CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230601105830.13168-4-jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jan Kara 2023-06-01 12:58:24 +02:00 • committed by Justin Hammond
parent 6a399c4c20
commit 712f6af364
3 changed files with 46 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

42
fs/inode.c
View file

@ -1023,6 +1023,48 @@ void discard_new_inode(struct inode *inode)
}
EXPORT_SYMBOL(discard_new_inode);
/**
* lock_two_inodes - lock two inodes (may be regular files but also dirs)
*
* Lock any non-NULL argument. The caller must make sure that if he is passing
* in two directories, one is not ancestor of the other. Zero, one or two
* objects may be locked by this function.
*
* @inode1: first inode to lock
* @inode2: second inode to lock
* @subclass1: inode lock subclass for the first lock obtained
* @subclass2: inode lock subclass for the second lock obtained
*/
void lock_two_inodes(struct inode *inode1, struct inode *inode2,
unsigned subclass1, unsigned subclass2)
{
if (!inode1 || !inode2) {
/*
* Make sure @subclass1 will be used for the acquired lock.
* This is not strictly necessary (no current caller cares) but
* let's keep things consistent.
*/
if (!inode1)
swap(inode1, inode2);
goto lock;
}
/*
* If one object is directory and the other is not, we must make sure
* to lock directory first as the other object may be its child.
*/
if (S_ISDIR(inode2->i_mode) == S_ISDIR(inode1->i_mode)) {
if (inode1 > inode2)
swap(inode1, inode2);
} else if (!S_ISDIR(inode1->i_mode))
swap(inode1, inode2);
lock:
if (inode1)
inode_lock_nested(inode1, subclass1);
if (inode2 && inode2 != inode1)
inode_lock_nested(inode2, subclass2);
}
/**
* lock_two_nondirectories - take two i_mutexes on non-directory objects
*

2
fs/internal.h
View file

@ -152,6 +152,8 @@ extern void inode_add_lru(struct inode *inode);
int dentry_needs_remove_privs(struct user_namespace *, struct dentry *dentry);
bool in_group_or_capable(struct user_namespace *mnt_userns,
const struct inode *inode, kgid_t gid);
void lock_two_inodes(struct inode *inode1, struct inode *inode2,
unsigned subclass1, unsigned subclass2);
/*
* fs-writeback.c

4
fs/namei.c
View file

@ -2984,8 +2984,8 @@ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
return p;
}
inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
lock_two_inodes(p1->d_inode, p2->d_inode,
I_MUTEX_PARENT, I_MUTEX_PARENT2);
return NULL;
}
EXPORT_SYMBOL(lock_rename);