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Thu, 26 Feb 2026 21:31:52 +0800 (CST) X-QQ-SSF: 0000000000000000000000000000000 X-QQ-GoodBg: 1 X-BIZMAIL-ID: 1048834162358125244 EX-QQ-RecipientCnt: 6 From: Morduan Zang To: bfoster@redhat.com Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, Morduan Zang Subject: [PATCH] mm: fix pagecache_isize_extended() early-return bypass for large folio mappings Date: Thu, 26 Feb 2026 21:31:49 +0800 Message-ID: <3F3A46783F8E9D52+20260226133149.79586-1-zhangdandan@uniontech.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20240919160741.208162-3-bfoster@redhat.com> References: <20240919160741.208162-3-bfoster@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-QQ-SENDSIZE: 520 Feedback-ID: zesmtpip:uniontech.com:qybglogicsvrgz:qybglogicsvrgz6b-0 X-QQ-XMAILINFO: ODcDgdcDagQKK73kbnoKVnPAelgFd7Q6Mg6OyC7hgcKFpHFWBkzjjlmp g5Rq9T2TLhJC0skg/q0ul79P4ZzcquUzKn/uvFOZY11/U23Buz22qL+kBfJbNX/ll4YLmj0 2zB4sAyugLaRRWWp4axXbr3I8NiqTWgTLX0nlkO7mZ4yivC45MMnCC+fFt9PaV0pW9gMlnz 9uUS4prTcLH/EsvYUYJQ3uFTRJ3iSsHlY93b9mUXLgytGgbQMVksS7uuzYvwT7kn0XcRrpU yy/CWG609P3JZgd4z0cFs0e4jTTKePY9/Da0zpxUTOwOsYFSBodddq0D6JB1svxvcB2Rpm3 uQdC2+RMqJKRY82HkXvPkaKPma8s5EqANcIUDMTBc0pT6Mtmu5YthikZOEQie0u0x49mWrW Tr+iv44nsnV2DqbEn9HCFvK4TrGH+VJb+rndyDgn/vZwJRxGuRsyEiN4FVgjOVX63GYLQ2p klBBDahAm0C00dBanm5HLp/DGP+XodoBy5PzQgLE4gAaZRMFaLwu0evWbND/gsQRbz4LzAw cWAmKcum8VbFW/mLo+XTAA4KE4GD02ufecukPzyzDdbwjP1WznIkOniXHsKrCFwa/AHxL4j CcCIxZ1bldViPLk223Zcpc/RxUR5GQOCgxWQ2xFw8lpKfnE1YfCHgXmWvsnyGSG1wHmPrWU l0iO83vJskwMJr5yD92dIu2TlEHl5/iVlyGyRGTRvX7AK5vrxY8NOYCDX0r9dcYQo14DC2Z gsoLWMslbMvwGFs3+KHAuQrsqq+kNAJ+3cXtvHS+vQdQOS4MJRC9htVepg/v1pkJjqiGJtT LXVhdLOsaAACn44UZHu7/fQNhS0EOYoX7PCI4dYFOoj4hu5MdkFo4YKxCyk13EnU5fvG4vK eGwMoq8p6DdOVH4pqdp0fx8LdfvuWMbSsUrgghp8WjmQ3sr9kPnPhdaIT4IgDqZP445jrGS C7oxVE8g3bNNaZTRyD34GCCgxfl0C2+bJeSaHJ8K67KdT/VmE2LbANPh7WOgnq3mEiWLIQ8 rCIzBYnQ== X-QQ-XMRINFO: OD9hHCdaPRBwH5bRRRw8tsiH4UAatJqXfg== X-QQ-RECHKSPAM: 0 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E53174000C X-Stat-Signature: 984ik3d14hckykijnjjbsjc7zwmtg5p9 X-Rspam-User: X-HE-Tag: 1772112768-685365 X-HE-Meta: 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 7sdH+vY1 QwNVZHOqh0c3IgIRwwzacIx9EcFNAmeI1QJzJcd+9Up96xf3DOyTjSVLzcOoln72yUE+Thl4Otpg0Qc4cL9rsNksaDnnPA7E6u+7KASnxz7ZqzGvlcyGPAD5BVE3aqE/thjP2eHzaghzNHl4vb+8yV3fYXzm8k7DcbrN+I40J0Vf25rY0Ha4YjokzcK+bjdWEam6UiglqnwoCz2Ys47IanMHs+Z8+PZPXbMZBpOFTe93oILGZYpS3T/UjMgCj0V2Mr9r8+uM3ZTxZhGHtJ+5zyk62SEvaQBokctjwxEm+8RBur7lz/bi984QaK6Nybn/Ljsu8s9anVHNETlJJu8nzsBaKFMUy8aB2LB7XuDp4/rFlY0RKFwKgdBjR4rLEkJdyyj0kGb47YyAuXEE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: pagecache_isize_extended() has two early-return guards that were designed for the traditional sub-page block-size case: Guard 1: if (from >= to || bsize >= PAGE_SIZE) return; Guard 2: rounded_from = round_up(from, bsize); if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1))) return; Guard 1 was originally "bsize == PAGE_SIZE" and was widened to "bsize >= PAGE_SIZE" by commit 2ebe90dab980 ("mm: convert pagecache_isize_extended to use a folio"). The rationale is correct for the traditional buffer_head path: when the block size equals the page size, every folio covers exactly one block, so writeback's EOF handling (e.g. iomap_writepage_handle_eof()) zeros the post-EOF tail of the folio before writing it out, and no action is needed here. Guard 2 covers the case where @from rounded up to the next block boundary is already PAGE_SIZE-aligned, meaning no hole block straddles a page boundary. Both guards are correct for the traditional case. However, commit 52aecaee1c26 ("mm: zero range of eof folio exposed by inode size extension") added post-EOF zeroing inside pagecache_isize_extended() to handle dirty folios that will not go through writeback before the new i_size becomes visible. That zeroing code is placed after both guards, so it is unreachable whenever either guard fires. The same stale-data window is also covered by xfstests generic/363 which uses fsx with "-e 1" (EOF pollution mode) and exercises a broad range of size-changing operations. Fixes: 52aecaee1c26 ("mm: zero range of eof folio exposed by inode size extension") Fixes: 2ebe90dab980 ("mm: convert pagecache_isize_extended to use a folio") Signed-off-by: Morduan Zang --- mm/truncate.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/mm/truncate.c b/mm/truncate.c index 12467c1bd711..d3e473a206b3 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -847,13 +847,32 @@ void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to) WARN_ON(to > inode->i_size); - if (from >= to || bsize >= PAGE_SIZE) + if (from >= to) return; + + /* + * For filesystems with bsize >= PAGE_SIZE, the traditional buffer_head + * path handles post-EOF zeroing correctly at writeback time. However, + * with large folios enabled, a single folio can span multiple PAGE_SIZE + * blocks, so mmap writes beyond EOF within the same folio are not zeroed + * at writeback time before i_size is extended. We must handle this here. + */ + if (bsize >= PAGE_SIZE) { + /* + * Only needed if the mapping supports large folios, since otherwise + * each folio is exactly one page and writeback handles EOF zeroing. + */ + if (!mapping_large_folio_support(inode->i_mapping)) + return; + goto find_folio; + } + /* Page straddling @from will not have any hole block created? */ rounded_from = round_up(from, bsize); if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1))) return; +find_folio: folio = filemap_lock_folio(inode->i_mapping, from / PAGE_SIZE); /* Folio not cached? Nothing to do */ if (IS_ERR(folio)) -- 2.50.1