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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id a30sm1269538qtn.4.2021.04.21.17.39.15 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Wed, 21 Apr 2021 17:39:16 -0700 (PDT) Date: Wed, 21 Apr 2021 17:39:14 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: Hugh Dickins , Matthew Wilcox , William Kucharski , Christoph Hellwig , Jan Kara , Dave Chinner , Johannes Weiner , "Kirill A. Shutemov" , Yang Shi , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 2/2] mm/filemap: fix mapping_seek_hole_data on THP & 32-bit In-Reply-To: Message-ID: References: User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org No problem on 64-bit without huge pages, but xfstests generic/285 and other SEEK_HOLE/SEEK_DATA tests have regressed on huge tmpfs, and on 32-bit architectures, with the new mapping_seek_hole_data(). Several different bugs turned out to need fixing. u64 casts added to stop unfortunate sign-extension when shifting (and let's use shifts throughout, rather than mixed with * and /). Use round_up() when advancing pos, to stop assuming that pos was already THP-aligned when advancing it by THP-size. (But I believe this use of round_up() assumes that any THP must be THP-aligned: true while tmpfs enforces that alignment, and is the only fs with FS_THP_SUPPORT; but might need to be generalized in the future? If I try to generalize it right now, I'm sure to get it wrong!) Use xas_set() when iterating away from a THP, so that xa_index stays in synch with start, instead of drifting away to return bogus offset. Check start against end to avoid wrapping 32-bit xa_index to 0 (and to handle these additional cases, seek_data or not, it's easier to break the loop than goto: so rearrange exit from the function). Fixes: 41139aa4c3a3 ("mm/filemap: add mapping_seek_hole_data") Signed-off-by: Hugh Dickins --- mm/filemap.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) --- 5.12-rc8/mm/filemap.c 2021-02-26 19:42:39.812156085 -0800 +++ linux/mm/filemap.c 2021-04-20 23:20:20.509464440 -0700 @@ -2671,8 +2671,8 @@ unsigned int seek_page_size(struct xa_st loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start, loff_t end, int whence) { - XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT); - pgoff_t max = (end - 1) / PAGE_SIZE; + XA_STATE(xas, &mapping->i_pages, (u64)start >> PAGE_SHIFT); + pgoff_t max = (u64)(end - 1) >> PAGE_SHIFT; bool seek_data = (whence == SEEK_DATA); struct page *page; @@ -2681,7 +2681,8 @@ loff_t mapping_seek_hole_data(struct add rcu_read_lock(); while ((page = find_get_entry(&xas, max, XA_PRESENT))) { - loff_t pos = xas.xa_index * PAGE_SIZE; + loff_t pos = (u64)xas.xa_index << PAGE_SHIFT; + unsigned int seek_size; if (start < pos) { if (!seek_data) @@ -2689,25 +2690,25 @@ loff_t mapping_seek_hole_data(struct add start = pos; } - pos += seek_page_size(&xas, page); + seek_size = seek_page_size(&xas, page); + pos = round_up((u64)pos + 1, seek_size); start = page_seek_hole_data(&xas, mapping, page, start, pos, seek_data); if (start < pos) goto unlock; + if (start >= end) + break; + if (seek_size > PAGE_SIZE) + xas_set(&xas, (u64)pos >> PAGE_SHIFT); if (!xa_is_value(page)) put_page(page); } - rcu_read_unlock(); - if (seek_data) - return -ENXIO; - goto out; - + start = -ENXIO; unlock: rcu_read_unlock(); - if (!xa_is_value(page)) + if (page && !xa_is_value(page)) put_page(page); -out: if (start > end) return end; return start;