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xfs: don't allocate COW blocks for zeroing holes or unwritten extents

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The iomap zeroing interface is smart enough to skip zeroing holes or
unwritten extents.  Don't subvert this logic for reflink files.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Christoph Hellwig 2018-03-01 14:10:31 -08:00 • committed by Darrick J. Wong
parent 5b4c845ea4
commit 172ed391f6
1 changed files with 10 additions and 1 deletions
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11
fs/xfs/xfs_iomap.c
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@ -955,6 +955,13 @@ static inline bool imap_needs_alloc(struct inode *inode,
(IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);
}
static inline bool needs_cow_for_zeroing(struct xfs_bmbt_irec *imap, int nimaps)
{
return nimaps &&
imap->br_startblock != HOLESTARTBLOCK &&
imap->br_state != XFS_EXT_UNWRITTEN;
}
static inline bool need_excl_ilock(struct xfs_inode *ip, unsigned flags)
{
/*
@ -1024,7 +1031,9 @@ xfs_file_iomap_begin(
goto out_unlock;
}
if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) {
if (xfs_is_reflink_inode(ip) &&
((flags & IOMAP_WRITE) ||
((flags & IOMAP_ZERO) && needs_cow_for_zeroing(&imap, nimaps)))) {
if (flags & IOMAP_DIRECT) {
/*
* A reflinked inode will result in CoW alloc.