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From: Eric Biggers <ebiggers@kernel.org>
To: Daeho Jeong <daeho43@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com,
	Daeho Jeong <daehojeong@google.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix race of pending_pages in decompression
Date: Thu, 3 Dec 2020 20:01:45 -0800	[thread overview]
Message-ID: <X8m0qbd7rvQyiwOt@sol.localdomain> (raw)
In-Reply-To: <CACOAw_wTFsfgLfrWKRoM1o_HQorJE-=2ztZftQTn+comcpmHxQ@mail.gmail.com>

On Fri, Dec 04, 2020 at 12:43:23PM +0900, Daeho Jeong wrote:
> STEP_VERITY is enabled by f2fs_need_verity() and the function is like below.
> We already know the second condition (idx < DIV_ROUND_UP...) is
> satisfied when invoking f2fs_alloc_dic().
> 
> static inline bool f2fs_need_verity(const struct inode *inode, pgoff_t idx)
> {
>         return fsverity_active(inode) &&
>                idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
> }

Are you sure?  I thought that compression (and encryption) apply to the whole
file, including any Merkle tree blocks past i_size.

Also, even if you include the i_size check, it's still wrong to check
fsverity_active() in the middle of the I/O because FS_IOC_ENABLE_VERITY can
execute concurrently, causing fsverity_active() to return false at the beginning
of the I/O and true later in the I/O.  It needs to be checked only once, at the
beginning...

- Eric

WARNING: multiple messages have this Message-ID (diff)
From: Eric Biggers <ebiggers@kernel.org>
To: Daeho Jeong <daeho43@gmail.com>
Cc: Daeho Jeong <daehojeong@google.com>,
	kernel-team@android.com, linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix race of pending_pages in decompression
Date: Thu, 3 Dec 2020 20:01:45 -0800	[thread overview]
Message-ID: <X8m0qbd7rvQyiwOt@sol.localdomain> (raw)
In-Reply-To: <CACOAw_wTFsfgLfrWKRoM1o_HQorJE-=2ztZftQTn+comcpmHxQ@mail.gmail.com>

On Fri, Dec 04, 2020 at 12:43:23PM +0900, Daeho Jeong wrote:
> STEP_VERITY is enabled by f2fs_need_verity() and the function is like below.
> We already know the second condition (idx < DIV_ROUND_UP...) is
> satisfied when invoking f2fs_alloc_dic().
> 
> static inline bool f2fs_need_verity(const struct inode *inode, pgoff_t idx)
> {
>         return fsverity_active(inode) &&
>                idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
> }

Are you sure?  I thought that compression (and encryption) apply to the whole
file, including any Merkle tree blocks past i_size.

Also, even if you include the i_size check, it's still wrong to check
fsverity_active() in the middle of the I/O because FS_IOC_ENABLE_VERITY can
execute concurrently, causing fsverity_active() to return false at the beginning
of the I/O and true later in the I/O.  It needs to be checked only once, at the
beginning...

- Eric


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  reply	other threads:[~2020-12-04  4:02 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-04  0:58 [PATCH] f2fs: fix race of pending_pages in decompression Daeho Jeong
2020-12-04  0:58 ` [f2fs-dev] " Daeho Jeong
2020-12-04  3:28 ` Eric Biggers
2020-12-04  3:28   ` Eric Biggers
2020-12-04  3:43   ` Daeho Jeong
2020-12-04  3:43     ` Daeho Jeong
2020-12-04  4:01     ` Eric Biggers [this message]
2020-12-04  4:01       ` Eric Biggers
2020-12-04  4:31       ` Daeho Jeong
2020-12-04  4:31         ` Daeho Jeong
2020-12-04  4:48         ` Daeho Jeong
2020-12-04  4:48           ` Daeho Jeong
2020-12-04  4:51           ` Eric Biggers
2020-12-04  4:51             ` Eric Biggers
2020-12-04  5:00             ` Daeho Jeong
2020-12-04  5:00               ` Daeho Jeong
2020-12-04  5:18               ` Eric Biggers
2020-12-04  5:18                 ` Eric Biggers
2020-12-04  7:01                 ` Daeho Jeong
2020-12-04  7:01                   ` Daeho Jeong
2020-12-04 18:29                   ` Jaegeuk Kim
2020-12-04 18:29                     ` Jaegeuk Kim
2020-12-05  3:40                     ` Daeho Jeong
2020-12-05  3:40                       ` Daeho Jeong

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