linux-kernel - Re: [PATCH V2] fs/ntfs3: Add missing direct_IO in ntfs_aops

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Message-ID: <20250416061827.2995095-1-lizhi.xu@windriver.com>
Date: Wed, 16 Apr 2025 14:18:27 +0800
From: Lizhi Xu <lizhi.xu@...driver.com>
To: <hch@...radead.org>
CC: <almaz.alexandrovich@...agon-software.com>, <brauner@...nel.org>,
        <jack@...e.cz>, <linux-fsdevel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <lizhi.xu@...driver.com>,
        <ntfs3@...ts.linux.dev>,
        <syzbot+e36cc3297bd3afd25e19@...kaller.appspotmail.com>,
        <syzkaller-bugs@...glegroups.com>, <viro@...iv.linux.org.uk>
Subject: Re: [PATCH V2] fs/ntfs3: Add missing direct_IO in ntfs_aops_cmpr

On Tue, 15 Apr 2025 23:05:56 -0700, Christoph Hellwig wrote:
> > In the reproducer, the second file passed in by the system call sendfile()
> > sets the file flag O_DIRECT when opening the file, which bypasses the page
> > cache and accesses the direct io interface of the ntfs3 file system.
> > However, ntfs3 does not set direct_IO for compressed files in ntfs_aops_cmpr.
> 
> Not allowing direct I/O is perfectly fine.  If you think you need to
> support direct I/O for this case it is also fine.  But none of this
> has anything to do with 'can use the page cache' and there are also
The "The ntfs3 can use the page cache directly" I mentioned in the patch
is to explain that the calltrace is the direct I/O of ntfs3 called from
generic_file_read_iter().