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xfs: Use struct xfs_bmdr_block instead of struct xfs_btree_block to calculate root node size 

The incore data fork of an inode stores the bmap btree root node as 'struct
xfs_btree_block'. However, the ondisk version of the inode stores the bmap
btree root node as a 'struct xfs_bmdr_block'.

xfs_bmap_add_attrfork_btree() checks if the btree root node fits inside the
data fork of the inode. However, it incorrectly uses 'struct xfs_btree_block'
to compute the size of the bmap btree root node. Since size of 'struct
xfs_btree_block' is larger than that of 'struct xfs_bmdr_block',
xfs_bmap_add_attrfork_btree() could end up unnecessarily demoting the current
root node as the child of newly allocated root node.

This commit optimizes space usage by modifying xfs_bmap_add_attrfork_btree()
to use 'struct xfs_bmdr_block' to check if the bmap btree root node fits
inside the data fork of the inode.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
This commit is contained in:
Chandan Babu R 2021-04-02 15:07:33 -07:00 committed by Darrick J. Wong
parent fcb62c2803
commit b6785e279d
1 changed files with 3 additions and 1 deletions
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4
fs/xfs/libxfs/xfs_bmap.c
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@ -927,13 +927,15 @@ xfs_bmap_add_attrfork_btree(
xfs_inode_t *ip, /* incore inode pointer */
int *flags) /* inode logging flags */
{
struct xfs_btree_block *block = ip->i_df.if_broot;
xfs_btree_cur_t *cur; /* btree cursor */
int error; /* error return value */
xfs_mount_t *mp; /* file system mount struct */
int stat; /* newroot status */
mp = ip->i_mount;
if (ip->i_df.if_broot_bytes <= XFS_IFORK_DSIZE(ip))
if (XFS_BMAP_BMDR_SPACE(block) <= XFS_IFORK_DSIZE(ip))
*flags |= XFS_ILOG_DBROOT;
else {
cur = xfs_bmbt_init_cursor(mp, tp, ip, XFS_DATA_FORK);