[XFS] Return case-insensitive match for dentry cache
This implements the code to store the actual filename found during a lookup in the dentry cache and to avoid multiple entries in the dcache pointing to the same inode. To avoid polluting the dcache, we implement a new directory inode operations for lookup. xfs_vn_ci_lookup() stores the correct case name in the dcache. The "actual name" is only allocated and returned for a case- insensitive match and not an actual match. Another unusual interaction with the dcache is not storing negative dentries like other filesystems doing a d_add(dentry, NULL) when an ENOENT is returned. During the VFS lookup, if a dentry returned has no inode, dput is called and ENOENT is returned. By not doing a d_add, this actually removes it completely from the dcache to be reused. create/rename have to be modified to support unhashed dentries being passed in. SGI-PV: 981521 SGI-Modid: xfs-linux-melb:xfs-kern:31208a Signed-off-by: NBarry Naujok <bnaujok@sgi.com> Signed-off-by: NChristoph Hellwig <hch@infradead.org>
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