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Sat, 18 Apr 2026 07:33:22 +0000 (GMT) Received: from li-dc0c254c-257c-11b2-a85c-98b6c1322444.ibm.com (unknown [9.39.28.145]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTPS; Sat, 18 Apr 2026 07:33:22 +0000 (GMT) Date: Sat, 18 Apr 2026 13:03:00 +0530 From: Ojaswin Mujoo To: "Pankaj Raghav (Samsung)" Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, djwong@kernel.org, john.g.garry@oracle.com, willy@infradead.org, hch@lst.de, ritesh.list@gmail.com, jack@suse.cz, Luis Chamberlain , dgc@kernel.org, tytso@mit.edu, p.raghav@samsung.com, andres@anarazel.de, brauner@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v2 2/5] iomap: Add initial support for buffered RWF_WRITETHROUGH Message-ID: References: <2dmo4my5rml4ymfuw5afc2fnbcxn2l3w3bz2boj4eevognilni@vgy4vwlikqx7> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2dmo4my5rml4ymfuw5afc2fnbcxn2l3w3bz2boj4eevognilni@vgy4vwlikqx7> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE4MDA2NiBTYWx0ZWRfX/TvXlMxHfyfq mjqgI2sJREm5linMAn5otpl2Cp8gk5T3mnsNhQWfbd0jC6p30ZEMwGzcpq/bXaKUNLp4zcxn4IR VblcCW2ZmaCsMmMEKGQzE0obGxltOZpPzAoI92G4CCXsbmZBvZLu3O1YzRW9NqBR+bNQPu6W8wf Rs0iWhSDx6ObytfUPqITj+kbwP+PvlCf8E2b+Sd78+/kC0B0R9fdf62OSAm2LpjQWVKci9liaUJ sBQXEGgMa63ruur59OP+nFCBsdxHbnMPf//9WDf8WJqOUJkaOp0XXZdG7Q6weq+5OcgMg5HUNGp LiftT+ii/XwXjQS1+U2AGw5Mnd7oyNRtYuyTgy1awNGOd8N3G/b0YvSf+NpI2s9pxobazU71RJ2 FayHYkh/EjyAR6hbBmICqsjVLRJTfPGGPsNc4ruaAJsBJilsXq/zVCXwEFy8RGEeB4Hc8go9iuN q7RgqGJNqgtrb0MIbTw== X-Proofpoint-GUID: lZmppBzJlcsLpXL5MluOHtnYPsOuBekb X-Authority-Analysis: v=2.4 cv=SOJykuvH c=1 sm=1 tr=0 ts=69e333ca cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=J4mrUdnwTHBwwN0GybQA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: AlFrBinGigvIOFIpwWjlosqGmBosXcyT X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-18_02,2026-04-17_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 priorityscore=1501 lowpriorityscore=0 clxscore=1015 phishscore=0 suspectscore=0 adultscore=0 impostorscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604180066 X-Stat-Signature: eiidkyijcjcx5aa3uznn9btj1fh5ohiz X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: D6185C0008 X-Rspam-User: X-HE-Tag: 1776497619-234121 X-HE-Meta: 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 EOXmJ+gC 64J9dlik54ZcEy7CKXkDb8TKFoh3UkkG46RUfA5PNioo4ZjdWSoXpOBbogSVRljqcPiCslfS1fosSgJ7DlkhrhWiUmesTzQ+qAGksVNKayleE53LbReu3MQAJ3UWIvJ/WNiRRkp2W0YNZuVnUlYs+qsi1549ZNGYFrlPaxn6qY+WMVBdli720oQruGTT+3IenoBCWFWj196nMDHfq7tc/rq6WrWCW0SgCbGDMU3qqKCmYmpExj7ji2e4Jd+g1kp57i3f4aDKI9gYWWa6rf0Eg/c+uAlc+381URnvDG9Cy/e/9hA3YPZqSSHY9eZfVEzlcmVvGChNMswIAztT+xHa2u2zpZ1qvS8TmBwL2lAUa6sgYgnvLnIWxm7h+KAOo+hzQlMvp8CJTxGG7rTpnt+oclMY7bAkXB/WPdNXAEQfcoTHmh9S2BKXAMpzczA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 17, 2026 at 06:13:31AM +0200, Pankaj Raghav (Samsung) wrote: > > > 3.3. Wait for any current writeback to complete and then call > > folio_mkclean() to prevent mmap writes from changing it. > > 3.4. Start writeback on the folio > > > + > > +/** > > + * iomap_writethrough_begin - prepare the various structures for writethrough > > + * @folio: folio to prepare for writethrough > > + * @off: offset of write within folio > > + * @len: len of write within folio > > + * > > + * This function does the major preparation work needed before starting the > > + * writethrough. The main task is to prepare folio for writeththrough by blocking > > + * mmap writes and setting writeback on it. Further, we must clear the write range > > + * to non-dirty. If this results in the complete folio becoming non-dirty, then we > > + * need to clear the master dirty bit. > > + */ > > +static void iomap_folio_prepare_writethrough(struct folio *folio, size_t off, > > + size_t len) > > +{ > > + bool fully_written; > > + u64 zero = 0; > > + > > + if (folio_test_writeback(folio)) > > + folio_wait_writeback(folio); > > + > > + if (folio_mkclean(folio)) > > + folio_mark_dirty(folio); > > + > > + /* > > + * We might either write through the complete folio or a partial folio > > + * writethrough might result in all blocks becoming non-dirty, so we need to > > + * check and mark the folio clean if that is the case. > > + */ > > + fully_written = (off == 0 && len == folio_size(folio)); > > + iomap_clear_range_dirty(folio, off, len); > > + if (fully_written || > > + !iomap_find_dirty_range(folio, &zero, folio_size(folio))) > > + folio_clear_dirty_for_writethrough(folio); > > I get the point where you want to prevent mmap writes before the current > writeback completes. It is not very obvious to me why folio_mkclean > and folio_mark_dirty had to be moved out and then we call the > folio_clear_dirty_for_writethrough wrapper. Anyway those calls are made > after we do folio_wait_writeback right? > Is to cover the cases where we do partial write in which case we don't > end up calling folio_clear_dirty_for_io? If that is the case, then a small > comment on top of folio_mkclean would make it a bit more clear. Hey Pankaj, Yes you are right, we need to call folio_wait_writeback() and mkclean() for partial or complete writes. However, clearing of foliodirty bit and accounting shall only be done when the complete folio becomes clean, and hence we call folio_clear_dirty_for_writethrough() only for those cases. I will add a more clear comment for this in v3. Thanks, Ojaswin > > -- > Pankaj