From: Christoph Hellwig <hch@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Arnd Bergmann <arnd@arndb.de>,
linux-nvdimm@lists.01.org, linux-api@vger.kernel.org,
linux-xfs@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
linux-ext4@vger.kernel.org
Subject: Re: [PATCH 01/17] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags
Date: Fri, 20 Oct 2017 00:27:07 -0700 [thread overview]
Message-ID: <20171020072707.GA18000@infradead.org> (raw)
In-Reply-To: <20171019125817.11580-2-jack@suse.cz>
> if (file) {
> struct inode *inode = file_inode(file);
> + unsigned long flags_mask = file->f_op->mmap_supported_flags;
> +
> + if (!flags_mask)
> + flags_mask = LEGACY_MAP_MASK;
>
> switch (flags & MAP_TYPE) {
> case MAP_SHARED:
> + /*
> + * Silently ignore unsupported flags - MAP_SHARED has
> + * traditionally behaved like that and we don't want
> + * to break compatibility.
> + */
> + flags &= flags_mask;
> + /*
> + * Force use of MAP_SHARED_VALIDATE with non-legacy
> + * flags. E.g. MAP_SYNC is dangerous to use with
> + * MAP_SHARED as you don't know which consistency model
> + * you will get.
> + */
> + flags &= LEGACY_MAP_MASK;
> + /* fall through */
> + case MAP_SHARED_VALIDATE:
> + if (flags & ~flags_mask)
> + return -EOPNOTSUPP;
Hmmm. I'd expect this to worth more like:
case MAP_SHARED:
/* Ignore all new flags that need validation: */
flags &= LEGACY_MAP_MASK;
/*FALLTHROUGH*/
case MAP_SHARED_VALIDATE:
if (flags & ~file->f_op->mmap_supported_flags)
return -EOPNOTSUPP;
with the legacy mask always implicitly support as indicated in my
comment to the XFS patch.
Although even the ignoring in MAP_SHARED seems dangerous, but I guess
we need that to keep strict backwards compatibility. In world I'd
rather do
case MAP_SHARED:
if (flags & ~LEGACY_MAP_MASK)
return -EINVAL;
next prev parent reply other threads:[~2017-10-20 7:27 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-19 12:57 [PATCH 0/17 v4] dax, ext4, xfs: Synchronous page faults Jan Kara
2017-10-19 12:58 ` [PATCH 12/17] mm: Define MAP_SYNC and VM_SYNC flags Jan Kara
[not found] ` <20171019125817.11580-1-jack-AlSwsSmVLrQ@public.gmane.org>
2017-10-19 12:58 ` [PATCH 01/17] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags Jan Kara
[not found] ` <20171019125817.11580-2-jack-AlSwsSmVLrQ@public.gmane.org>
2017-10-19 16:48 ` Dan Williams
2017-10-20 7:27 ` Christoph Hellwig [this message]
[not found] ` <20171020072707.GA18000-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2017-10-24 13:08 ` Jan Kara
2017-10-19 12:58 ` [PATCH 02/17] mm: Remove VM_FAULT_HWPOISON_LARGE_MASK Jan Kara
2017-10-19 12:58 ` [PATCH 03/17] dax: Simplify arguments of dax_insert_mapping() Jan Kara
2017-10-19 12:58 ` [PATCH 04/17] dax: Factor out getting of pfn out of iomap Jan Kara
2017-10-19 12:58 ` [PATCH 05/17] dax: Create local variable for VMA in dax_iomap_pte_fault() Jan Kara
2017-10-19 12:58 ` [PATCH 06/17] dax: Create local variable for vmf->flags & FAULT_FLAG_WRITE test Jan Kara
2017-10-19 12:58 ` [PATCH 07/17] dax: Inline dax_insert_mapping() into the callsite Jan Kara
2017-10-19 12:58 ` [PATCH 08/17] dax: Inline dax_pmd_insert_mapping() " Jan Kara
2017-10-19 12:58 ` [PATCH 09/17] dax: Fix comment describing dax_iomap_fault() Jan Kara
2017-10-19 12:58 ` [PATCH 10/17] dax: Allow dax_iomap_fault() to return pfn Jan Kara
2017-10-19 12:58 ` [PATCH 11/17] dax: Allow tuning whether dax_insert_mapping_entry() dirties entry Jan Kara
2017-10-19 12:58 ` [PATCH 13/17] dax, iomap: Add support for synchronous faults Jan Kara
2017-10-19 12:58 ` [PATCH 14/17] dax: Implement dax_finish_sync_fault() Jan Kara
2017-10-19 12:58 ` [PATCH 15/17] ext4: Simplify error handling in ext4_dax_huge_fault() Jan Kara
2017-10-19 12:58 ` [PATCH 16/17] ext4: Support for synchronous DAX faults Jan Kara
2017-10-19 12:58 ` [PATCH 17/17] xfs: support " Jan Kara
2017-10-19 13:17 ` Christoph Hellwig
2017-10-19 12:58 ` [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC Jan Kara
[not found] ` <20171019125817.11580-19-jack-AlSwsSmVLrQ@public.gmane.org>
2017-10-20 21:47 ` Ross Zwisler
[not found] ` <20171020214753.GA15733-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-10-24 13:27 ` Jan Kara
[not found] ` <20171024132713.GD8556-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2017-10-24 14:55 ` Ross Zwisler
2017-10-24 15:23 [PATCH 0/17 v5] dax, ext4, xfs: Synchronous page faults Jan Kara
[not found] ` <20171024152415.22864-1-jack-AlSwsSmVLrQ@public.gmane.org>
2017-10-24 15:23 ` [PATCH 01/17] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags Jan Kara
[not found] ` <20171024152415.22864-2-jack-AlSwsSmVLrQ@public.gmane.org>
2017-10-24 21:21 ` Ross Zwisler
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