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Wong" To: "Matthew Wilcox (Oracle)" Cc: linux-xfs@vger.kernel.org, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/3] xfs: Remove xfs_filemap_map_pages() wrapper Message-ID: References: <20230208145335.307287-1-willy@infradead.org> <20230208145335.307287-2-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230208145335.307287-2-willy@infradead.org> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BE1C5140015 X-Rspam-User: X-Stat-Signature: zudksoq7yk3wgoqoonmpnzfmjwip9fb7 X-HE-Tag: 1675874361-258020 X-HE-Meta: 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 m2L+arEC r6N1nB1ekCiPev7e+vptMZKwuW3XxF2CHFNhbiN/ipHJbp830WwUijnklAdjTdRjeaupJF6eYNbNJfq0ero0BAOv/wPzWAXNiqicrmPp+JUyFgEVMaKCaz3BazKhZ+5UU7p2GN6JA7Yhf8d8a2XP/mXG7bwDjeP2fdJpQqoh3n86EnRJaClbPXeBfJFaxZJbCOXQMkwB6VJP00dQfGA+ds1qQF2Geg1jJEPPyUcpqbZ+pEq8BdZxAGO3AIMYeNJLQoGHDgjG+a1ryZfhrw0QYz4gUtCnFSPa6iLWY3HZcmcLSZMqi3zLE/iyGcovnhaXj4dZ9xo/zAVkOyKVJiPNvn8N1Bbx7P2vjaL3+/DEOZF6+zLR3bQ/dHv/skSy81Zk4o9Bj0gnsQKTPt5Lhs4lvK7bEEg== 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: On Wed, Feb 08, 2023 at 02:53:33PM +0000, Matthew Wilcox (Oracle) wrote: > XFS doesn't actually need to be holding the XFS_MMAPLOCK_SHARED > to do this, any more than it needs the XFS_MMAPLOCK_SHARED for a > read() that hits in the page cache. Hmm. From commit cd647d5651c0 ("xfs: use MMAPLOCK around filemap_map_pages()"): The page faultround path ->map_pages is implemented in XFS via filemap_map_pages(). This function checks that pages found in page cache lookups have not raced with truncate based invalidation by checking page->mapping is correct and page->index is within EOF. However, we've known for a long time that this is not sufficient to protect against races with invalidations done by operations that do not change EOF. e.g. hole punching and other fallocate() based direct extent manipulations. The way we protect against these races is we wrap the page fault operations in a XFS_MMAPLOCK_SHARED lock so they serialise against fallocate and truncate before calling into the filemap function that processes the fault. Do the same for XFS's ->map_pages implementation to close this potential data corruption issue. How do we prevent faultaround from racing with fallocate and reflink calls that operate below EOF? --D > Signed-off-by: Matthew Wilcox (Oracle) > --- > fs/xfs/xfs_file.c | 17 +---------------- > 1 file changed, 1 insertion(+), 16 deletions(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index 705250f9f90a..528fc538b6b9 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -1388,25 +1388,10 @@ xfs_filemap_pfn_mkwrite( > return __xfs_filemap_fault(vmf, PE_SIZE_PTE, true); > } > > -static vm_fault_t > -xfs_filemap_map_pages( > - struct vm_fault *vmf, > - pgoff_t start_pgoff, > - pgoff_t end_pgoff) > -{ > - struct inode *inode = file_inode(vmf->vma->vm_file); > - vm_fault_t ret; > - > - xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED); > - ret = filemap_map_pages(vmf, start_pgoff, end_pgoff); > - xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED); > - return ret; > -} > - > static const struct vm_operations_struct xfs_file_vm_ops = { > .fault = xfs_filemap_fault, > .huge_fault = xfs_filemap_huge_fault, > - .map_pages = xfs_filemap_map_pages, > + .map_pages = filemap_map_pages, > .page_mkwrite = xfs_filemap_page_mkwrite, > .pfn_mkwrite = xfs_filemap_pfn_mkwrite, > }; > -- > 2.35.1 >