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Commit 309c8480 authored by Dave Chinner's avatar Dave Chinner Committed by Alex Elder
Browse files

xfs: delayed alloc blocks beyond EOF are valid after writeback 



There is an assumption in the parts of XFS that flushing a dirty
file will make all the delayed allocation blocks disappear from an
inode. That is, that after calling xfs_flush_pages() then
ip->i_delayed_blks will be zero.

This is an invalid assumption as we may have specualtive
preallocation beyond EOF and they are recorded in
ip->i_delayed_blks. A flush of the dirty pages of an inode will not
change the state of these blocks beyond EOF, so a non-zero
deeelalloc block count after a flush is valid.

The bmap code has an invalid ASSERT() that needs to be removed, and
the swapext code has a bug in that while it swaps the data forks
around, it fails to swap the i_delayed_blks counter associated with
the fork and hence can get the block accounting wrong.

Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent 90810b9e

fs/xfs/xfs_bmap.c

+7 −2
Original line number Original line Diff line number Diff line
@@ -5471,8 +5471,13 @@ xfs_getbmap( 
			if (error)

			if (error)

				goto out_unlock_iolock;

				goto out_unlock_iolock;

		}

		}



		/*

		ASSERT(ip->i_delayed_blks == 0);

		 * even after flushing the inode, there can still be delalloc

		 * blocks on the inode beyond EOF due to speculative

		 * preallocation. These are not removed until the release

		 * function is called or the inode is inactivated. Hence we

		 * cannot assert here that ip->i_delayed_blks == 0.

		 */

	}

	}





	lock = xfs_ilock_map_shared(ip);

	lock = xfs_ilock_map_shared(ip);

fs/xfs/xfs_dfrag.c

+13 −0
Original line number Original line Diff line number Diff line
@@ -377,6 +377,19 @@ xfs_swap_extents( 
	ip->i_d.di_format = tip->i_d.di_format;

	ip->i_d.di_format = tip->i_d.di_format;

	tip->i_d.di_format = tmp;

	tip->i_d.di_format = tmp;





	/*

	 * The extents in the source inode could still contain speculative

	 * preallocation beyond EOF (e.g. the file is open but not modified

	 * while defrag is in progress). In that case, we need to copy over the

	 * number of delalloc blocks the data fork in the source inode is

	 * tracking beyond EOF so that when the fork is truncated away when the

	 * temporary inode is unlinked we don't underrun the i_delayed_blks

	 * counter on that inode.

	 */

	ASSERT(tip->i_delayed_blks == 0);

	tip->i_delayed_blks = ip->i_delayed_blks;

	ip->i_delayed_blks = 0;



	ilf_fields = XFS_ILOG_CORE;

	ilf_fields = XFS_ILOG_CORE;





	switch(ip->i_d.di_format) {

	switch(ip->i_d.di_format) {