xfs: handle EOF correctly in xfs_vm_writepage
We need to zero out part of a page which beyond EOF before setting uptodate, otherwise, mapread or write will see non-zero data beyond EOF. Based on the code in fs/buffer.c and the following ext4 commit: ext4: handle EOF correctly in ext4_bio_write_page() And yes, I wish we had a good test case for it. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Mark Tinguely <tinguely@sgi.com> Signed-off-by: Ben Myers <bpm@sgi.com>
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@ -927,11 +927,26 @@ xfs_vm_writepage(
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end_index = offset >> PAGE_CACHE_SHIFT;
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last_index = (offset - 1) >> PAGE_CACHE_SHIFT;
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if (page->index >= end_index) {
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if ((page->index >= end_index + 1) ||
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!(i_size_read(inode) & (PAGE_CACHE_SIZE - 1))) {
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unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1);
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/*
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* Just skip the page if it is fully outside i_size, e.g. due
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* to a truncate operation that is in progress.
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*/
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if (page->index >= end_index + 1 || offset_into_page == 0) {
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unlock_page(page);
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return 0;
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}
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/*
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* The page straddles i_size. It must be zeroed out on each
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* and every writepage invocation because it may be mmapped.
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* "A file is mapped in multiples of the page size. For a file
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* that is not a multiple of the page size, the remaining
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* memory is zeroed when mapped, and writes to that region are
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* not written out to the file."
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*/
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zero_user_segment(page, offset_into_page, PAGE_CACHE_SIZE);
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}
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end_offset = min_t(unsigned long long,
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