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Fri, 21 Nov 2025 15:22:49 +0000 (UTC) Received: from bfoster.redhat.com (unknown [10.22.64.29]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id CF354180049F; Fri, 21 Nov 2025 15:22:48 +0000 (UTC) From: Brian Foster To: linux-mm@kvack.org Cc: Hugh Dickins , Baolin Wang Subject: [PATCH v3 2/3] tmpfs: zero post-eof folio ranges on swapout Date: Fri, 21 Nov 2025 10:22:45 -0500 Message-ID: <20251121152246.1023918-3-bfoster@redhat.com> In-Reply-To: <20251121152246.1023918-1-bfoster@redhat.com> References: <20251121152246.1023918-1-bfoster@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: RD3U6Meo4p8haWip5sLMHfWTCJrH6H2LGZqOPpd6bJ0_1763738569 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: BDFF740006 X-Stat-Signature: jur58cdww51gxb7yaej6cwy8mpwmsu4q X-HE-Tag: 1763738572-278568 X-HE-Meta: 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 iNMnSDCU f+cRd4vhVIELUvsNKNijyTMhaPunEEX48Z7TnroiFpugD3MFY0lbJJ+Ww2c/HmxPjDFKRAF+YE+JInqesOLuAncW41VJ8Tjx9bfFWgNC00mewV+9m/BAzGH8Cvsh9bAVX9xezXYX5zlPwfZmy13macmzTP+RGNIZ4kEwDuw+qNRJ582MVroZ5u6hhFrgU8BWPj5nlxb602VpV4NaanzCOeevS1GDItkFgwLzHcx6V/Qfbqw/tWN6gmMhTzBVtI6rRaGOcZasvKFIoY7wbemslQMhI7qFS2obV2Dgyj5bOw2X9U72o+dgIK9to8CqdrP2BjQb7sLHn/tGE12vkp93Vv961ztkGa1/fcpm+FEmsnwVXyjIVkRnAY568AQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Zero post-eof folios at swap out time to help preserve POSIX requirements and facilitate efficient post-eof zeroing during extending operations. This uses an analogous approach to pagecache writeback to ensure post-eof ranges are zeroed on-disk. This facilitates file extension zeroing by allowing it to skip swapped out folios that might have been preallocated beyond the original i_size. Signed-off-by: Brian Foster --- mm/shmem.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 651602460770..97ca2b3dd1b9 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1577,6 +1577,8 @@ int shmem_writeout(struct folio *folio, struct swap_iocb **plug, struct inode *inode = mapping->host; struct shmem_inode_info *info = SHMEM_I(inode); struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); + loff_t i_size = i_size_read(inode); + pgoff_t end_index = DIV_ROUND_UP(i_size, PAGE_SIZE); pgoff_t index; int nr_pages; bool split = false; @@ -1596,9 +1598,9 @@ int shmem_writeout(struct folio *folio, struct swap_iocb **plug, * (unless fallocate has been used to preallocate beyond EOF). */ if (folio_test_large(folio)) { - index = shmem_fallocend(inode, - DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE)); - if ((index > folio->index && index < folio_next_index(folio)) || + pgoff_t fallocend = shmem_fallocend(inode, end_index); + if ((fallocend > folio->index && + fallocend < folio_next_index(folio)) || !IS_ENABLED(CONFIG_THP_SWAP)) split = true; } @@ -1642,8 +1644,20 @@ int shmem_writeout(struct folio *folio, struct swap_iocb **plug, goto redirty; } - if (!folio_test_uptodate(folio)) { - folio_zero_range(folio, 0, folio_size(folio)); + /* + * Ranges beyond EOF must be zeroed at writeout time. This mirrors + * traditional writeback behavior and facilitates zeroing on file size + * changes without having to swap back in. + */ + if (!folio_test_uptodate(folio) || + folio_next_index(folio) >= end_index) { + size_t from = offset_in_folio(folio, i_size); + + if (!folio_test_uptodate(folio) || index >= end_index) + folio_zero_segment(folio, 0, folio_size(folio)); + else if (from) + folio_zero_segment(folio, from, folio_size(folio)); + flush_dcache_folio(folio); folio_mark_uptodate(folio); } -- 2.51.1