--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2020-2022, Red Hat, Inc.
+ * All Rights Reserved.
+ */
+
+#include "libxfs_priv.h"
+#include "libxfs.h"
+#include "libxfs_io.h"
+#include "init.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_log_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_inode.h"
+#include "xfs_trans.h"
+#include "xfs_ag.h"
+#include "iunlink.h"
+#include "xfs_trace.h"
+
+/* in memory log item structure */
+struct xfs_iunlink_item {
+ struct xfs_inode *ip;
+ struct xfs_perag *pag;
+ xfs_agino_t next_agino;
+ xfs_agino_t old_agino;
+};
+
+/*
+ * Look up the inode cluster buffer and log the on-disk unlinked inode change
+ * we need to make.
+ */
+static int
+xfs_iunlink_log_dinode(
+ struct xfs_trans *tp,
+ struct xfs_iunlink_item *iup)
+{
+ struct xfs_mount *mp = tp->t_mountp;
+ struct xfs_inode *ip = iup->ip;
+ struct xfs_dinode *dip;
+ struct xfs_buf *ibp;
+ int offset;
+ int error;
+
+ error = xfs_imap_to_bp(mp, tp, &ip->i_imap, &ibp);
+ if (error)
+ return error;
+ /*
+ * Don't log the unlinked field on stale buffers as this may be the
+ * transaction that frees the inode cluster and relogging the buffer
+ * here will incorrectly remove the stale state.
+ */
+ if (ibp->b_flags & LIBXFS_B_STALE)
+ goto out;
+
+ dip = xfs_buf_offset(ibp, ip->i_imap.im_boffset);
+
+ /* Make sure the old pointer isn't garbage. */
+ if (be32_to_cpu(dip->di_next_unlinked) != iup->old_agino) {
+ xfs_inode_verifier_error(ip, -EFSCORRUPTED, __func__, dip,
+ sizeof(*dip), __this_address);
+ error = -EFSCORRUPTED;
+ goto out;
+ }
+
+ trace_xfs_iunlink_update_dinode(mp, iup->pag->pag_agno,
+ XFS_INO_TO_AGINO(mp, ip->i_ino),
+ be32_to_cpu(dip->di_next_unlinked), iup->next_agino);
+
+ dip->di_next_unlinked = cpu_to_be32(iup->next_agino);
+ offset = ip->i_imap.im_boffset +
+ offsetof(struct xfs_dinode, di_next_unlinked);
+
+ xfs_dinode_calc_crc(mp, dip);
+ xfs_trans_inode_buf(tp, ibp);
+ xfs_trans_log_buf(tp, ibp, offset, offset + sizeof(xfs_agino_t) - 1);
+ return 0;
+out:
+ xfs_trans_brelse(tp, ibp);
+ return error;
+}
+
+/*
+ * Initialize the inode log item for a newly allocated (in-core) inode.
+ *
+ * Inode extents can only reside within an AG. Hence specify the starting
+ * block for the inode chunk by offset within an AG as well as the
+ * length of the allocated extent.
+ *
+ * This joins the item to the transaction and marks it dirty so
+ * that we don't need a separate call to do this, nor does the
+ * caller need to know anything about the iunlink item.
+ */
+int
+xfs_iunlink_log_inode(
+ struct xfs_trans *tp,
+ struct xfs_inode *ip,
+ struct xfs_perag *pag,
+ xfs_agino_t next_agino)
+{
+ struct xfs_iunlink_item iup = {
+ .ip = ip,
+ .pag = pag,
+ .next_agino = next_agino,
+ .old_agino = ip->i_next_unlinked,
+ };
+
+ ASSERT(xfs_verify_agino_or_null(pag, next_agino));
+ ASSERT(xfs_verify_agino_or_null(pag, ip->i_next_unlinked));
+
+ /*
+ * Since we're updating a linked list, we should never find that the
+ * current pointer is the same as the new value, unless we're
+ * terminating the list.
+ */
+ if (ip->i_next_unlinked == next_agino) {
+ if (next_agino != NULLAGINO)
+ return -EFSCORRUPTED;
+ return 0;
+ }
+
+ return xfs_iunlink_log_dinode(tp, &iup);
+}
+
+/*
+ * Load the inode @next_agino into the cache and set its prev_unlinked pointer
+ * to @prev_agino. Caller must hold the AGI to synchronize with other changes
+ * to the unlinked list.
+ */
+int
+xfs_iunlink_reload_next(
+ struct xfs_trans *tp,
+ struct xfs_buf *agibp,
+ xfs_agino_t prev_agino,
+ xfs_agino_t next_agino)
+{
+ struct xfs_perag *pag = agibp->b_pag;
+ struct xfs_mount *mp = pag->pag_mount;
+ struct xfs_inode *next_ip = NULL;
+ xfs_ino_t ino;
+ int error;
+
+ ASSERT(next_agino != NULLAGINO);
+
+ ino = XFS_AGINO_TO_INO(mp, pag->pag_agno, next_agino);
+ error = libxfs_iget(mp, tp, ino, XFS_IGET_UNTRUSTED, &next_ip);
+ if (error)
+ return error;
+
+ /* If this is not an unlinked inode, something is very wrong. */
+ if (VFS_I(next_ip)->i_nlink != 0) {
+ error = -EFSCORRUPTED;
+ goto rele;
+ }
+
+ next_ip->i_prev_unlinked = prev_agino;
+ trace_xfs_iunlink_reload_next(next_ip);
+rele:
+ xfs_irele(next_ip);
+ return error;
+}
#include "xfs_ialloc.h"
#include "xfs_health.h"
#include "xfs_bmap.h"
+#include "xfs_trace.h"
+#include "xfs_ag.h"
+#include "iunlink.h"
uint16_t
xfs_flags2diflags(
xfs_trans_log_inode(tp, ip, flags);
}
+
+/*
+ * In-Core Unlinked List Lookups
+ * =============================
+ *
+ * Every inode is supposed to be reachable from some other piece of metadata
+ * with the exception of the root directory. Inodes with a connection to a
+ * file descriptor but not linked from anywhere in the on-disk directory tree
+ * are collectively known as unlinked inodes, though the filesystem itself
+ * maintains links to these inodes so that on-disk metadata are consistent.
+ *
+ * XFS implements a per-AG on-disk hash table of unlinked inodes. The AGI
+ * header contains a number of buckets that point to an inode, and each inode
+ * record has a pointer to the next inode in the hash chain. This
+ * singly-linked list causes scaling problems in the iunlink remove function
+ * because we must walk that list to find the inode that points to the inode
+ * being removed from the unlinked hash bucket list.
+ *
+ * Hence we keep an in-memory double linked list to link each inode on an
+ * unlinked list. Because there are 64 unlinked lists per AGI, keeping pointer
+ * based lists would require having 64 list heads in the perag, one for each
+ * list. This is expensive in terms of memory (think millions of AGs) and cache
+ * misses on lookups. Instead, use the fact that inodes on the unlinked list
+ * must be referenced at the VFS level to keep them on the list and hence we
+ * have an existence guarantee for inodes on the unlinked list.
+ *
+ * Given we have an existence guarantee, we can use lockless inode cache lookups
+ * to resolve aginos to xfs inodes. This means we only need 8 bytes per inode
+ * for the double linked unlinked list, and we don't need any extra locking to
+ * keep the list safe as all manipulations are done under the AGI buffer lock.
+ * Keeping the list up to date does not require memory allocation, just finding
+ * the XFS inode and updating the next/prev unlinked list aginos.
+ */
+
+/*
+ * Update the prev pointer of the next agino. Returns -ENOLINK if the inode
+ * is not in cache.
+ */
+static int
+xfs_iunlink_update_backref(
+ struct xfs_perag *pag,
+ xfs_agino_t prev_agino,
+ xfs_agino_t next_agino)
+{
+ struct xfs_inode *ip;
+
+ /* No update necessary if we are at the end of the list. */
+ if (next_agino == NULLAGINO)
+ return 0;
+
+ ip = xfs_iunlink_lookup(pag, next_agino);
+ if (!ip)
+ return -ENOLINK;
+
+ ip->i_prev_unlinked = prev_agino;
+ return 0;
+}
+
+/*
+ * Point the AGI unlinked bucket at an inode and log the results. The caller
+ * is responsible for validating the old value.
+ */
+STATIC int
+xfs_iunlink_update_bucket(
+ struct xfs_trans *tp,
+ struct xfs_perag *pag,
+ struct xfs_buf *agibp,
+ unsigned int bucket_index,
+ xfs_agino_t new_agino)
+{
+ struct xfs_agi *agi = agibp->b_addr;
+ xfs_agino_t old_value;
+ int offset;
+
+ ASSERT(xfs_verify_agino_or_null(pag, new_agino));
+
+ old_value = be32_to_cpu(agi->agi_unlinked[bucket_index]);
+ trace_xfs_iunlink_update_bucket(tp->t_mountp, pag->pag_agno, bucket_index,
+ old_value, new_agino);
+
+ /*
+ * We should never find the head of the list already set to the value
+ * passed in because either we're adding or removing ourselves from the
+ * head of the list.
+ */
+ if (old_value == new_agino) {
+ xfs_buf_mark_corrupt(agibp);
+ xfs_ag_mark_sick(pag, XFS_SICK_AG_AGI);
+ return -EFSCORRUPTED;
+ }
+
+ agi->agi_unlinked[bucket_index] = cpu_to_be32(new_agino);
+ offset = offsetof(struct xfs_agi, agi_unlinked) +
+ (sizeof(xfs_agino_t) * bucket_index);
+ xfs_trans_log_buf(tp, agibp, offset, offset + sizeof(xfs_agino_t) - 1);
+ return 0;
+}
+
+static int
+xfs_iunlink_insert_inode(
+ struct xfs_trans *tp,
+ struct xfs_perag *pag,
+ struct xfs_buf *agibp,
+ struct xfs_inode *ip)
+{
+ struct xfs_mount *mp = tp->t_mountp;
+ struct xfs_agi *agi = agibp->b_addr;
+ xfs_agino_t next_agino;
+ xfs_agino_t agino = XFS_INO_TO_AGINO(mp, ip->i_ino);
+ short bucket_index = agino % XFS_AGI_UNLINKED_BUCKETS;
+ int error;
+
+ /*
+ * Get the index into the agi hash table for the list this inode will
+ * go on. Make sure the pointer isn't garbage and that this inode
+ * isn't already on the list.
+ */
+ next_agino = be32_to_cpu(agi->agi_unlinked[bucket_index]);
+ if (next_agino == agino ||
+ !xfs_verify_agino_or_null(pag, next_agino)) {
+ xfs_buf_mark_corrupt(agibp);
+ xfs_ag_mark_sick(pag, XFS_SICK_AG_AGI);
+ return -EFSCORRUPTED;
+ }
+
+ /*
+ * Update the prev pointer in the next inode to point back to this
+ * inode.
+ */
+ error = xfs_iunlink_update_backref(pag, agino, next_agino);
+ if (error == -ENOLINK)
+ error = xfs_iunlink_reload_next(tp, agibp, agino, next_agino);
+ if (error)
+ return error;
+
+ if (next_agino != NULLAGINO) {
+ /*
+ * There is already another inode in the bucket, so point this
+ * inode to the current head of the list.
+ */
+ error = xfs_iunlink_log_inode(tp, ip, pag, next_agino);
+ if (error)
+ return error;
+ ip->i_next_unlinked = next_agino;
+ }
+
+ /* Point the head of the list to point to this inode. */
+ ip->i_prev_unlinked = NULLAGINO;
+ return xfs_iunlink_update_bucket(tp, pag, agibp, bucket_index, agino);
+}
+
+/*
+ * This is called when the inode's link count has gone to 0 or we are creating
+ * a tmpfile via O_TMPFILE. The inode @ip must have nlink == 0.
+ *
+ * We place the on-disk inode on a list in the AGI. It will be pulled from this
+ * list when the inode is freed.
+ */
+int
+xfs_iunlink(
+ struct xfs_trans *tp,
+ struct xfs_inode *ip)
+{
+ struct xfs_mount *mp = tp->t_mountp;
+ struct xfs_perag *pag;
+ struct xfs_buf *agibp;
+ int error;
+
+ ASSERT(VFS_I(ip)->i_nlink == 0);
+ ASSERT(VFS_I(ip)->i_mode != 0);
+ trace_xfs_iunlink(ip);
+
+ pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
+
+ /* Get the agi buffer first. It ensures lock ordering on the list. */
+ error = xfs_read_agi(pag, tp, 0, &agibp);
+ if (error)
+ goto out;
+
+ error = xfs_iunlink_insert_inode(tp, pag, agibp, ip);
+out:
+ xfs_perag_put(pag);
+ return error;
+}
+
+static int
+xfs_iunlink_remove_inode(
+ struct xfs_trans *tp,
+ struct xfs_perag *pag,
+ struct xfs_buf *agibp,
+ struct xfs_inode *ip)
+{
+ struct xfs_mount *mp = tp->t_mountp;
+ struct xfs_agi *agi = agibp->b_addr;
+ xfs_agino_t agino = XFS_INO_TO_AGINO(mp, ip->i_ino);
+ xfs_agino_t head_agino;
+ short bucket_index = agino % XFS_AGI_UNLINKED_BUCKETS;
+ int error;
+
+ trace_xfs_iunlink_remove(ip);
+
+ /*
+ * Get the index into the agi hash table for the list this inode will
+ * go on. Make sure the head pointer isn't garbage.
+ */
+ head_agino = be32_to_cpu(agi->agi_unlinked[bucket_index]);
+ if (!xfs_verify_agino(pag, head_agino)) {
+ XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp,
+ agi, sizeof(*agi));
+ xfs_ag_mark_sick(pag, XFS_SICK_AG_AGI);
+ return -EFSCORRUPTED;
+ }
+
+ /*
+ * Set our inode's next_unlinked pointer to NULL and then return
+ * the old pointer value so that we can update whatever was previous
+ * to us in the list to point to whatever was next in the list.
+ */
+ error = xfs_iunlink_log_inode(tp, ip, pag, NULLAGINO);
+ if (error)
+ return error;
+
+ /*
+ * Update the prev pointer in the next inode to point back to previous
+ * inode in the chain.
+ */
+ error = xfs_iunlink_update_backref(pag, ip->i_prev_unlinked,
+ ip->i_next_unlinked);
+ if (error == -ENOLINK)
+ error = xfs_iunlink_reload_next(tp, agibp, ip->i_prev_unlinked,
+ ip->i_next_unlinked);
+ if (error)
+ return error;
+
+ if (head_agino != agino) {
+ struct xfs_inode *prev_ip;
+
+ prev_ip = xfs_iunlink_lookup(pag, ip->i_prev_unlinked);
+ if (!prev_ip) {
+ xfs_inode_mark_sick(ip, XFS_SICK_INO_CORE);
+ return -EFSCORRUPTED;
+ }
+
+ error = xfs_iunlink_log_inode(tp, prev_ip, pag,
+ ip->i_next_unlinked);
+ prev_ip->i_next_unlinked = ip->i_next_unlinked;
+ } else {
+ /* Point the head of the list to the next unlinked inode. */
+ error = xfs_iunlink_update_bucket(tp, pag, agibp, bucket_index,
+ ip->i_next_unlinked);
+ }
+
+ ip->i_next_unlinked = NULLAGINO;
+ ip->i_prev_unlinked = 0;
+ return error;
+}
+
+/*
+ * Pull the on-disk inode from the AGI unlinked list.
+ */
+int
+xfs_iunlink_remove(
+ struct xfs_trans *tp,
+ struct xfs_perag *pag,
+ struct xfs_inode *ip)
+{
+ struct xfs_buf *agibp;
+ int error;
+
+ trace_xfs_iunlink_remove(ip);
+
+ /* Get the agi buffer first. It ensures lock ordering on the list. */
+ error = xfs_read_agi(pag, tp, 0, &agibp);
+ if (error)
+ return error;
+
+ return xfs_iunlink_remove_inode(tp, pag, agibp, ip);
+}
projects / users / hch / xfsprogs.git / commitdiff