From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Storing errors in the XArray Date: Fri, 15 Dec 2017 09:10:12 -0800 Message-ID: <20171215171012.GA11918@bombadil.infradead.org> References: <20171206004159.3755-1-willy@infradead.org> <20171206004159.3755-9-willy@infradead.org> <66ad068b-1973-ca41-7bbf-8a0634cc488d@infradead.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=iJH7l8lpuFlxh4QnVPh6zRoyLwVI5jfRKefeePYqrhk=; b=AtBMGvTSOaArkbzVoMwv79tY0 j7xSySmnT9hbS1wwsiW+CIp/klUi9G2CQpyla20/YOI5oz2TUgooWfPViMLYBGdSMBxeHfoqBH1Ce JrCvAbjFNoOD7qZtWDYQmhi0eQ92DqL6tNZNb9jVFOAVpHE7PkipAf7k5I3crNyLzMfbBX/0HlzFQ 8cgZLIjZ9ItFKVS6K2yMZLluz7CvmN+hhGAu3KsR5GRmNM6p/ntSK/IaaQuubr/t/IOxjsfZq9U5m qHH7gpvfWhdWH+w1sNWTCn8LJaV/r+xRW/elP3RM6b5GLpb/t9jYAtzszZ+ISWiLsdokErx9Hjz95 UdKFrBB2Q==; Content-Disposition: inline In-Reply-To: <66ad068b-1973-ca41-7bbf-8a0634cc488d@infradead.org> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Randy Dunlap Cc: Matthew Wilcox , Ross Zwisler , Jens Axboe , Rehas Sachdeva , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-nilfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org On Mon, Dec 11, 2017 at 03:10:22PM -0800, Randy Dunlap wrote: > > +The XArray does not support storing :c:func:`IS_ERR` pointers; some > > +conflict with data values and others conflict with entries the XArray > > +uses for its own purposes. If you need to store special values which > > +cannot be confused with real kernel pointers, the values 4, 8, ... 4092 > > +are available. > > or if I know that they values are errno-range values, I can just shift them > left by 2 to store them and then shift them right by 2 to use them? On further thought, I like this idea so much, it's worth writing helpers for this usage. And test-suite (also doubles as a demonstration of how to use it). diff --git a/include/linux/xarray.h b/include/linux/xarray.h index c616e9319c7c..53aa251df57a 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -232,6 +232,39 @@ static inline bool xa_is_value(const void *entry) return (unsigned long)entry & 1; } +/** + * xa_mk_errno() - Create an XArray entry from an error number. + * @error: Error number to store in XArray. + * + * Return: An entry suitable for storing in the XArray. + */ +static inline void *xa_mk_errno(long error) +{ + return (void *)(error << 2); +} + +/** + * xa_to_errno() - Get error number stored in an XArray entry. + * @entry: XArray entry. + * + * Return: The error number stored in the XArray entry. + */ +static inline unsigned long xa_to_errno(const void *entry) +{ + return (long)entry >> 2; +} + +/** + * xa_is_errno() - Determine if an entry is an errno. + * @entry: XArray entry. + * + * Return: True if the entry is an errno, false if it is a pointer. + */ +static inline bool xa_is_errno(const void *entry) +{ + return (((unsigned long)entry & 3) == 0) && (entry > (void *)-4096); +} + /** * xa_is_internal() - Is the entry an internal entry? * @entry: Entry retrieved from the XArray diff --git a/tools/testing/radix-tree/xarray-test.c b/tools/testing/radix-tree/xarray-test.c index 43111786ebdd..b843cedf3988 100644 --- a/tools/testing/radix-tree/xarray-test.c +++ b/tools/testing/radix-tree/xarray-test.c @@ -29,7 +29,13 @@ void check_xa_err(struct xarray *xa) assert(xa_err(xa_store(xa, 1, xa_mk_value(0), GFP_KERNEL)) == 0); assert(xa_err(xa_store(xa, 1, NULL, 0)) == 0); // kills the test-suite :-( -// assert(xa_err(xa_store(xa, 0, xa_mk_internal(0), 0)) == -EINVAL); +// assert(xa_err(xa_store(xa, 0, xa_mk_internal(0), 0)) == -EINVAL); + + assert(xa_err(xa_store(xa, 0, xa_mk_errno(-ENOMEM), GFP_KERNEL)) == 0); + assert(xa_err(xa_load(xa, 0)) == 0); + assert(xa_is_errno(xa_load(xa, 0)) == true); + assert(xa_to_errno(xa_load(xa, 0)) == -ENOMEM); + xa_erase(xa, 0); } void check_xa_tag(struct xarray *xa) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org