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ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize
commit fcf5ea10992fbac3c7473a1db33d56a139333cd1 upstream. ext4_find_unwritten_pgoff() does not properly handle a situation when starting index is in the middle of a page and blocksize < pagesize. The following command shows the bug on filesystem with 1k blocksize: xfs_io -f -c "falloc 0 4k" \ -c "pwrite 1k 1k" \ -c "pwrite 3k 1k" \ -c "seek -a -r 0" foo In this example, neither lseek(fd, 1024, SEEK_HOLE) nor lseek(fd, 2048, SEEK_DATA) will return the correct result. Fix the problem by neglecting buffers in a page before starting offset. Reported-by: Andreas Gruenbacher <agruenba@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Jan Kara <jack@suse.cz> CC: stable@vger.kernel.org # 3.8+ Signed-off-by: Willy Tarreau <w@1wt.eu>
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@ -382,6 +382,8 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
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lastoff = page_offset(page);
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bh = head = page_buffers(page);
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do {
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if (lastoff + bh->b_size <= startoff)
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goto next;
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if (buffer_uptodate(bh) ||
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buffer_unwritten(bh)) {
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if (whence == SEEK_DATA)
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@ -396,6 +398,7 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
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unlock_page(page);
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goto out;
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}
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next:
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lastoff += bh->b_size;
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bh = bh->b_this_page;
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} while (bh != head);
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