Received-SPF: pass (google.com: domain of linux-ext4-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 23 Sep 2022 01:45:44 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Sarthak Kukreti <sarthakkukreti@chromium.org>
Cc:     Christoph Hellwig <hch@infradead.org>, dm-devel@redhat.com,
        linux-block@vger.kernel.org, linux-ext4@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Jens Axboe <axboe@kernel.dk>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Alasdair Kergon <agk@redhat.com>,
        Mike Snitzer <snitzer@kernel.org>,
        Theodore Ts'o <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Bart Van Assche <bvanassche@google.com>,
        Daniil Lunev <dlunev@google.com>,
        Evan Green <evgreen@google.com>,
        Gwendal Grignou <gwendal@google.com>
Subject: Re: [PATCH RFC 4/8] fs: Introduce FALLOC_FL_PROVISION
Message-ID: <Yy1yOGy7yF4AShDB@infradead.org>
References: <20220915164826.1396245-1-sarthakkukreti@google.com>
 <20220915164826.1396245-5-sarthakkukreti@google.com>
 <YylweQAZkIdb5ixo@infradead.org>
 <CAG9=OMNoG01UUStNs_Zhsv6mXZw0M0q2v54ZriJvHZ4aspvjEQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAG9=OMNoG01UUStNs_Zhsv6mXZw0M0q2v54ZriJvHZ4aspvjEQ@mail.gmail.com>
Precedence: bulk

On Tue, Sep 20, 2022 at 10:54:32PM -0700, Sarthak Kukreti wrote:
> [ mmc0blkp1 | ext4(1) | sparse file | loop | dm-thinp | dm-thin | ext4(2) ]
> 
> would be predicated on the guarantees of fallocate() per allocation
> layer; if ext4(1) was replaced by a filesystem that did not support
> fallocate(), then there would be no guarantee that a write to a file
> on ext4(2) succeeds.

a write or any unlimited number of writes?