btrfs: Avoid truncate tailing page if fallocate range doesn't exceed inode size
Current code will always truncate tailing page if its alloc_start is smaller than inode size. For example, the file extent layout is like: 0 4K 8K 16K 32K |<-----Extent A---------------->| |<--Inode size: 18K---------->| But if calling fallocate even for range [0,4K), it will cause btrfs to re-truncate the range [16,32K), causing COW and a new extent. 0 4K 8K 16K 32K |///////| <- Fallocate call range |<-----Extent A-------->|<--B-->| The cause is quite easy, just a careless btrfs_truncate_inode() in a else branch without extra judgment. Fix it by add judgment on whether the fallocate range is beyond isize. Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com> Signed-off-by: Chris Mason <clm@fb.com>
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@ -2584,7 +2584,7 @@ static long btrfs_fallocate(struct file *file, int mode,
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alloc_start);
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if (ret)
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goto out;
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} else {
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} else if (offset + len > inode->i_size) {
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/*
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* If we are fallocating from the end of the file onward we
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* need to zero out the end of the page if i_size lands in the
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