fb102fe7fe
Although directory entry and parent pointer recordsets look very similar (name -> ino), there's one major difference between them: a file can be hardlinked from multiple parent directories with the same filename. This is common in shared container environments where a base directory tree might be hardlink-copied multiple times. IOWs the same 'ls' program might be hardlinked to multiple /srv/*/bin/ls paths. We don't want parent pointer operations to bog down on hash collisions between the same dirent name, so create a special hash function that mixes in the parent directory inode number. Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
140 lines
3.5 KiB
C
140 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2022-2024 Oracle.
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* All rights reserved.
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*/
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#include "xfs.h"
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#include "xfs_fs.h"
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#include "xfs_format.h"
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#include "xfs_da_format.h"
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#include "xfs_log_format.h"
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#include "xfs_shared.h"
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#include "xfs_trans_resv.h"
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#include "xfs_mount.h"
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#include "xfs_bmap_btree.h"
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#include "xfs_inode.h"
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#include "xfs_error.h"
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#include "xfs_trace.h"
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#include "xfs_trans.h"
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#include "xfs_da_btree.h"
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#include "xfs_attr.h"
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#include "xfs_dir2.h"
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#include "xfs_dir2_priv.h"
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#include "xfs_attr_sf.h"
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#include "xfs_bmap.h"
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#include "xfs_defer.h"
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#include "xfs_log.h"
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#include "xfs_xattr.h"
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#include "xfs_parent.h"
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#include "xfs_trans_space.h"
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/*
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* Parent pointer attribute handling.
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*
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* Because the attribute name is a filename component, it will never be longer
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* than 255 bytes and must not contain nulls or slashes. These are roughly the
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* same constraints that apply to attribute names.
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*
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* The attribute value must always be a struct xfs_parent_rec. This means the
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* attribute will never be in remote format because 12 bytes is nowhere near
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* xfs_attr_leaf_entsize_local_max() (~75% of block size).
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*
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* Creating a new parent attribute will always create a new attribute - there
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* should never, ever be an existing attribute in the tree for a new inode.
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* ENOSPC behavior is problematic - creating the inode without the parent
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* pointer is effectively a corruption, so we allow parent attribute creation
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* to dip into the reserve block pool to avoid unexpected ENOSPC errors from
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* occurring.
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*/
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/* Return true if parent pointer attr name is valid. */
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bool
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xfs_parent_namecheck(
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unsigned int attr_flags,
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const void *name,
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size_t length)
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{
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/*
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* Parent pointers always use logged operations, so there should never
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* be incomplete xattrs.
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*/
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if (attr_flags & XFS_ATTR_INCOMPLETE)
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return false;
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return xfs_dir2_namecheck(name, length);
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}
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/* Return true if parent pointer attr value is valid. */
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bool
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xfs_parent_valuecheck(
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struct xfs_mount *mp,
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const void *value,
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size_t valuelen)
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{
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const struct xfs_parent_rec *rec = value;
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if (!xfs_has_parent(mp))
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return false;
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/* The xattr value must be a parent record. */
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if (valuelen != sizeof(struct xfs_parent_rec))
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return false;
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/* The parent record must be local. */
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if (value == NULL)
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return false;
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/* The parent inumber must be valid. */
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if (!xfs_verify_dir_ino(mp, be64_to_cpu(rec->p_ino)))
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return false;
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return true;
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}
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/* Compute the attribute name hash for a parent pointer. */
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xfs_dahash_t
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xfs_parent_hashval(
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struct xfs_mount *mp,
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const uint8_t *name,
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int namelen,
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xfs_ino_t parent_ino)
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{
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struct xfs_name xname = {
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.name = name,
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.len = namelen,
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};
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/*
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* Use the same dirent name hash as would be used on the directory, but
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* mix in the parent inode number to avoid collisions on hardlinked
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* files with identical names but different parents.
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*/
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return xfs_dir2_hashname(mp, &xname) ^
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upper_32_bits(parent_ino) ^ lower_32_bits(parent_ino);
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}
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/* Compute the attribute name hash from the xattr components. */
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xfs_dahash_t
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xfs_parent_hashattr(
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struct xfs_mount *mp,
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const uint8_t *name,
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int namelen,
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const void *value,
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int valuelen)
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{
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const struct xfs_parent_rec *rec = value;
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/* Requires a local attr value in xfs_parent_rec format */
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if (valuelen != sizeof(struct xfs_parent_rec)) {
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ASSERT(valuelen == sizeof(struct xfs_parent_rec));
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return 0;
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}
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if (!value) {
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ASSERT(value != NULL);
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return 0;
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}
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return xfs_parent_hashval(mp, name, namelen, be64_to_cpu(rec->p_ino));
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}
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