Messages in this thread | | | Date | Sat, 17 Mar 2012 10:14:29 +0400 | Subject | Re: [ 10/41] CIFS: Do not kmalloc under the flocks spinlock | From | Pavel Shilovsky <> |
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17 марта 2012 г. 6:37 пользователь Ben Hutchings <ben@decadent.org.uk> написал: > On Fri, Mar 16, 2012 at 04:38:20PM -0700, Greg KH wrote: >> 3.2-stable review patch. If anyone has any objections, please let me know. >> >> ------------------ >> >> From: Pavel Shilovsky <piastry@etersoft.ru> >> >> commit d5751469f210d2149cc2159ffff66cbeef6da3f2 upstream. >> >> Reorganize the code to make the memory already allocated before >> spinlock'ed loop. >> >> Reviewed-by: Jeff Layton <jlayton@redhat.com> >> Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru> >> Signed-off-by: Steve French <sfrench@us.ibm.com> >> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >> >> --- >> fs/cifs/file.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++----------- >> 1 file changed, 56 insertions(+), 13 deletions(-) >> >> --- a/fs/cifs/file.c >> +++ b/fs/cifs/file.c > [....] >> @@ -940,29 +950,55 @@ cifs_push_posix_locks(struct cifsFileInf >> return rc; >> } >> >> + lock_flocks(); >> + cifs_for_each_lock(cfile->dentry->d_inode, before) { >> + if ((*before)->fl_flags & FL_POSIX) >> + count++; >> + } >> + unlock_flocks(); >> + >> INIT_LIST_HEAD(&locks_to_send); >> >> + /* >> + * Allocating count locks is enough because no locks can be added to >> + * the list while we are holding cinode->lock_mutex that protects >> + * locking operations of this inode. >> + */ >> + for (; i < count; i++) { >> + lck = kmalloc(sizeof(struct lock_to_push), GFP_KERNEL); >> + if (!lck) { >> + rc = -ENOMEM; >> + goto err_out; >> + } >> + list_add_tail(&lck->llist, &locks_to_send); >> + } >> + >> + i = 0; >> + el = locks_to_send.next; >> lock_flocks(); >> cifs_for_each_lock(cfile->dentry->d_inode, before) { >> + if (el == &locks_to_send) { >> + /* something is really wrong */ >> + cERROR(1, "Can't push all brlocks!"); >> + break; >> + } >> flock = *before; >> + if ((flock->fl_flags & FL_POSIX) == 0) >> + continue; > [...] > > If I understand the logic correctly, el == &locks_to_send means we > already used all the lock_to_push structures. (It should also be > equivalent to testing i == count. Why is i incremented but not > otherwise used in the loop?) > > But we test this before flock->fl_flags & FL_POSIX, which means we > don't know whether this lock actually needs to be assigned one of > those structures. So it appears that we might report a spurious error > if the lock list ends with a mandatory lock. If so, this is > relatively harmless but does need to be fixed. >
You are right here, thanks for the catch! I will repost the patch asap.
-- Best regards, Pavel Shilovsky. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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