openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

afs: Fix AFS file locking to allow fine grained locks 

Fix AFS file locking to allow fine grained locks as some applications, such
as firefox, won't work if they can't take such locks on certain state files
- thereby preventing the use of kAFS to distribute a home directory.

Note that this cannot be made completely functional as the protocol only
has provision for whole-file locks, so there exists the possibility of a
process deadlocking itself by getting a partial read-lock on a file first
and then trying to get a non-overlapping write-lock - but we got the
server's read lock with the first lock, so we're now stuck.

OpenAFS solves this by just granting any partial-range lock directly
without consulting the server - and hoping there's no remote collision.  I
want to implement that in a separate patch and it requires a bit more
thought.

Fixes: 8d6c554126b8 ("AFS: implement file locking")
Reported-by: Jonathan Billings <jsbillings@jsbillings.org>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2019-04-25 14:26:50 +01:00
parent a690f60a2b
commit 68ce801ffd
1 changed files with 9 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
fs/afs/flock.c
View File

@ -458,10 +458,6 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
_enter("{%llx:%llu},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
/* only whole-file locks are supported */
if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
return -EINVAL;
fl->fl_ops = &afs_lock_ops;
INIT_LIST_HEAD(&fl->fl_u.afs.link);
fl->fl_u.afs.state = AFS_LOCK_PENDING;
@ -613,10 +609,6 @@ static int afs_do_unlk(struct file *file, struct file_lock *fl)
/* Flush all pending writes before doing anything with locks. */
vfs_fsync(file, 0);
/* only whole-file unlocks are supported */
if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
return -EINVAL;
ret = posix_lock_file(file, fl, NULL);
_leave(" = %d [%u]", ret, vnode->lock_state);
return ret;
@ -644,12 +636,15 @@ static int afs_do_getlk(struct file *file, struct file_lock *fl)
goto error;
lock_count = READ_ONCE(vnode->status.lock_count);
if (lock_count > 0)
fl->fl_type = F_RDLCK;
else
fl->fl_type = F_WRLCK;
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
if (lock_count != 0) {
if (lock_count > 0)
fl->fl_type = F_RDLCK;
else
fl->fl_type = F_WRLCK;
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
fl->fl_pid = 0;
}
}
ret = 0;