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-rw-r--r--fs/aufs/plink.c516
1 files changed, 516 insertions, 0 deletions
diff --git a/fs/aufs/plink.c b/fs/aufs/plink.c
new file mode 100644
index 000000000000..718edb8827a3
--- /dev/null
+++ b/fs/aufs/plink.c
@@ -0,0 +1,516 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2019 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * pseudo-link
+ */
+
+#include "aufs.h"
+
+/*
+ * the pseudo-link maintenance mode.
+ * during a user process maintains the pseudo-links,
+ * prohibit adding a new plink and branch manipulation.
+ *
+ * Flags
+ * NOPLM:
+ * For entry functions which will handle plink, and i_mutex is already held
+ * in VFS.
+ * They cannot wait and should return an error at once.
+ * Callers has to check the error.
+ * NOPLMW:
+ * For entry functions which will handle plink, but i_mutex is not held
+ * in VFS.
+ * They can wait the plink maintenance mode to finish.
+ *
+ * They behave like F_SETLK and F_SETLKW.
+ * If the caller never handle plink, then both flags are unnecessary.
+ */
+
+int au_plink_maint(struct super_block *sb, int flags)
+{
+ int err;
+ pid_t pid, ppid;
+ struct task_struct *parent, *prev;
+ struct au_sbinfo *sbi;
+
+ SiMustAnyLock(sb);
+
+ err = 0;
+ if (!au_opt_test(au_mntflags(sb), PLINK))
+ goto out;
+
+ sbi = au_sbi(sb);
+ pid = sbi->si_plink_maint_pid;
+ if (!pid || pid == current->pid)
+ goto out;
+
+ /* todo: it highly depends upon /sbin/mount.aufs */
+ prev = NULL;
+ parent = current;
+ ppid = 0;
+ rcu_read_lock();
+ while (1) {
+ parent = rcu_dereference(parent->real_parent);
+ if (parent == prev)
+ break;
+ ppid = task_pid_vnr(parent);
+ if (pid == ppid) {
+ rcu_read_unlock();
+ goto out;
+ }
+ prev = parent;
+ }
+ rcu_read_unlock();
+
+ if (au_ftest_lock(flags, NOPLMW)) {
+ /* if there is no i_mutex lock in VFS, we don't need to wait */
+ /* AuDebugOn(!lockdep_depth(current)); */
+ while (sbi->si_plink_maint_pid) {
+ si_read_unlock(sb);
+ /* gave up wake_up_bit() */
+ wait_event(sbi->si_plink_wq, !sbi->si_plink_maint_pid);
+
+ if (au_ftest_lock(flags, FLUSH))
+ au_nwt_flush(&sbi->si_nowait);
+ si_noflush_read_lock(sb);
+ }
+ } else if (au_ftest_lock(flags, NOPLM)) {
+ AuDbg("ppid %d, pid %d\n", ppid, pid);
+ err = -EAGAIN;
+ }
+
+out:
+ return err;
+}
+
+void au_plink_maint_leave(struct au_sbinfo *sbinfo)
+{
+ spin_lock(&sbinfo->si_plink_maint_lock);
+ sbinfo->si_plink_maint_pid = 0;
+ spin_unlock(&sbinfo->si_plink_maint_lock);
+ wake_up_all(&sbinfo->si_plink_wq);
+}
+
+int au_plink_maint_enter(struct super_block *sb)
+{
+ int err;
+ struct au_sbinfo *sbinfo;
+
+ err = 0;
+ sbinfo = au_sbi(sb);
+ /* make sure i am the only one in this fs */
+ si_write_lock(sb, AuLock_FLUSH);
+ if (au_opt_test(au_mntflags(sb), PLINK)) {
+ spin_lock(&sbinfo->si_plink_maint_lock);
+ if (!sbinfo->si_plink_maint_pid)
+ sbinfo->si_plink_maint_pid = current->pid;
+ else
+ err = -EBUSY;
+ spin_unlock(&sbinfo->si_plink_maint_lock);
+ }
+ si_write_unlock(sb);
+
+ return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_DEBUG
+void au_plink_list(struct super_block *sb)
+{
+ int i;
+ struct au_sbinfo *sbinfo;
+ struct hlist_bl_head *hbl;
+ struct hlist_bl_node *pos;
+ struct au_icntnr *icntnr;
+
+ SiMustAnyLock(sb);
+
+ sbinfo = au_sbi(sb);
+ AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+ AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
+
+ for (i = 0; i < AuPlink_NHASH; i++) {
+ hbl = sbinfo->si_plink + i;
+ hlist_bl_lock(hbl);
+ hlist_bl_for_each_entry(icntnr, pos, hbl, plink)
+ AuDbg("%lu\n", icntnr->vfs_inode.i_ino);
+ hlist_bl_unlock(hbl);
+ }
+}
+#endif
+
+/* is the inode pseudo-linked? */
+int au_plink_test(struct inode *inode)
+{
+ int found, i;
+ struct au_sbinfo *sbinfo;
+ struct hlist_bl_head *hbl;
+ struct hlist_bl_node *pos;
+ struct au_icntnr *icntnr;
+
+ sbinfo = au_sbi(inode->i_sb);
+ AuRwMustAnyLock(&sbinfo->si_rwsem);
+ AuDebugOn(!au_opt_test(au_mntflags(inode->i_sb), PLINK));
+ AuDebugOn(au_plink_maint(inode->i_sb, AuLock_NOPLM));
+
+ found = 0;
+ i = au_plink_hash(inode->i_ino);
+ hbl = sbinfo->si_plink + i;
+ hlist_bl_lock(hbl);
+ hlist_bl_for_each_entry(icntnr, pos, hbl, plink)
+ if (&icntnr->vfs_inode == inode) {
+ found = 1;
+ break;
+ }
+ hlist_bl_unlock(hbl);
+ return found;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * generate a name for plink.
+ * the file will be stored under AUFS_WH_PLINKDIR.
+ */
+/* 20 is max digits length of ulong 64 */
+#define PLINK_NAME_LEN ((20 + 1) * 2)
+
+static int plink_name(char *name, int len, struct inode *inode,
+ aufs_bindex_t bindex)
+{
+ int rlen;
+ struct inode *h_inode;
+
+ h_inode = au_h_iptr(inode, bindex);
+ rlen = snprintf(name, len, "%lu.%lu", inode->i_ino, h_inode->i_ino);
+ return rlen;
+}
+
+struct au_do_plink_lkup_args {
+ struct dentry **errp;
+ struct qstr *tgtname;
+ struct dentry *h_parent;
+ struct au_branch *br;
+};
+
+static struct dentry *au_do_plink_lkup(struct qstr *tgtname,
+ struct dentry *h_parent,
+ struct au_branch *br)
+{
+ struct dentry *h_dentry;
+ struct inode *h_inode;
+
+ h_inode = d_inode(h_parent);
+ inode_lock_shared_nested(h_inode, AuLsc_I_CHILD2);
+ h_dentry = vfsub_lkup_one(tgtname, h_parent);
+ inode_unlock_shared(h_inode);
+ return h_dentry;
+}
+
+static void au_call_do_plink_lkup(void *args)
+{
+ struct au_do_plink_lkup_args *a = args;
+ *a->errp = au_do_plink_lkup(a->tgtname, a->h_parent, a->br);
+}
+
+/* lookup the plink-ed @inode under the branch at @bindex */
+struct dentry *au_plink_lkup(struct inode *inode, aufs_bindex_t bindex)
+{
+ struct dentry *h_dentry, *h_parent;
+ struct au_branch *br;
+ int wkq_err;
+ char a[PLINK_NAME_LEN];
+ struct qstr tgtname = QSTR_INIT(a, 0);
+
+ AuDebugOn(au_plink_maint(inode->i_sb, AuLock_NOPLM));
+
+ br = au_sbr(inode->i_sb, bindex);
+ h_parent = br->br_wbr->wbr_plink;
+ tgtname.len = plink_name(a, sizeof(a), inode, bindex);
+
+ if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID)) {
+ struct au_do_plink_lkup_args args = {
+ .errp = &h_dentry,
+ .tgtname = &tgtname,
+ .h_parent = h_parent,
+ .br = br
+ };
+
+ wkq_err = au_wkq_wait(au_call_do_plink_lkup, &args);
+ if (unlikely(wkq_err))
+ h_dentry = ERR_PTR(wkq_err);
+ } else
+ h_dentry = au_do_plink_lkup(&tgtname, h_parent, br);
+
+ return h_dentry;
+}
+
+/* create a pseudo-link */
+static int do_whplink(struct qstr *tgt, struct dentry *h_parent,
+ struct dentry *h_dentry, struct au_branch *br)
+{
+ int err;
+ struct path h_path = {
+ .mnt = au_br_mnt(br)
+ };
+ struct inode *h_dir, *delegated;
+
+ h_dir = d_inode(h_parent);
+ inode_lock_nested(h_dir, AuLsc_I_CHILD2);
+again:
+ h_path.dentry = vfsub_lkup_one(tgt, h_parent);
+ err = PTR_ERR(h_path.dentry);
+ if (IS_ERR(h_path.dentry))
+ goto out;
+
+ err = 0;
+ /* wh.plink dir is not monitored */
+ /* todo: is it really safe? */
+ if (d_is_positive(h_path.dentry)
+ && d_inode(h_path.dentry) != d_inode(h_dentry)) {
+ delegated = NULL;
+ err = vfsub_unlink(h_dir, &h_path, &delegated, /*force*/0);
+ if (unlikely(err == -EWOULDBLOCK)) {
+ pr_warn("cannot retry for NFSv4 delegation"
+ " for an internal unlink\n");
+ iput(delegated);
+ }
+ dput(h_path.dentry);
+ h_path.dentry = NULL;
+ if (!err)
+ goto again;
+ }
+ if (!err && d_is_negative(h_path.dentry)) {
+ delegated = NULL;
+ err = vfsub_link(h_dentry, h_dir, &h_path, &delegated);
+ if (unlikely(err == -EWOULDBLOCK)) {
+ pr_warn("cannot retry for NFSv4 delegation"
+ " for an internal link\n");
+ iput(delegated);
+ }
+ }
+ dput(h_path.dentry);
+
+out:
+ inode_unlock(h_dir);
+ return err;
+}
+
+struct do_whplink_args {
+ int *errp;
+ struct qstr *tgt;
+ struct dentry *h_parent;
+ struct dentry *h_dentry;
+ struct au_branch *br;
+};
+
+static void call_do_whplink(void *args)
+{
+ struct do_whplink_args *a = args;
+ *a->errp = do_whplink(a->tgt, a->h_parent, a->h_dentry, a->br);
+}
+
+static int whplink(struct dentry *h_dentry, struct inode *inode,
+ aufs_bindex_t bindex, struct au_branch *br)
+{
+ int err, wkq_err;
+ struct au_wbr *wbr;
+ struct dentry *h_parent;
+ char a[PLINK_NAME_LEN];
+ struct qstr tgtname = QSTR_INIT(a, 0);
+
+ wbr = au_sbr(inode->i_sb, bindex)->br_wbr;
+ h_parent = wbr->wbr_plink;
+ tgtname.len = plink_name(a, sizeof(a), inode, bindex);
+
+ /* always superio. */
+ if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID)) {
+ struct do_whplink_args args = {
+ .errp = &err,
+ .tgt = &tgtname,
+ .h_parent = h_parent,
+ .h_dentry = h_dentry,
+ .br = br
+ };
+ wkq_err = au_wkq_wait(call_do_whplink, &args);
+ if (unlikely(wkq_err))
+ err = wkq_err;
+ } else
+ err = do_whplink(&tgtname, h_parent, h_dentry, br);
+
+ return err;
+}
+
+/*
+ * create a new pseudo-link for @h_dentry on @bindex.
+ * the linked inode is held in aufs @inode.
+ */
+void au_plink_append(struct inode *inode, aufs_bindex_t bindex,
+ struct dentry *h_dentry)
+{
+ struct super_block *sb;
+ struct au_sbinfo *sbinfo;
+ struct hlist_bl_head *hbl;
+ struct hlist_bl_node *pos;
+ struct au_icntnr *icntnr;
+ int found, err, cnt, i;
+
+ sb = inode->i_sb;
+ sbinfo = au_sbi(sb);
+ AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+ AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
+
+ found = au_plink_test(inode);
+ if (found)
+ return;
+
+ i = au_plink_hash(inode->i_ino);
+ hbl = sbinfo->si_plink + i;
+ au_igrab(inode);
+
+ hlist_bl_lock(hbl);
+ hlist_bl_for_each_entry(icntnr, pos, hbl, plink) {
+ if (&icntnr->vfs_inode == inode) {
+ found = 1;
+ break;
+ }
+ }
+ if (!found) {
+ icntnr = container_of(inode, struct au_icntnr, vfs_inode);
+ hlist_bl_add_head(&icntnr->plink, hbl);
+ }
+ hlist_bl_unlock(hbl);
+ if (!found) {
+ cnt = au_hbl_count(hbl);
+#define msg "unexpectedly unbalanced or too many pseudo-links"
+ if (cnt > AUFS_PLINK_WARN)
+ AuWarn1(msg ", %d\n", cnt);
+#undef msg
+ err = whplink(h_dentry, inode, bindex, au_sbr(sb, bindex));
+ if (unlikely(err)) {
+ pr_warn("err %d, damaged pseudo link.\n", err);
+ au_hbl_del(&icntnr->plink, hbl);
+ iput(&icntnr->vfs_inode);
+ }
+ } else
+ iput(&icntnr->vfs_inode);
+}
+
+/* free all plinks */
+void au_plink_put(struct super_block *sb, int verbose)
+{
+ int i, warned;
+ struct au_sbinfo *sbinfo;
+ struct hlist_bl_head *hbl;
+ struct hlist_bl_node *pos, *tmp;
+ struct au_icntnr *icntnr;
+
+ SiMustWriteLock(sb);
+
+ sbinfo = au_sbi(sb);
+ AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+ AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
+
+ /* no spin_lock since sbinfo is write-locked */
+ warned = 0;
+ for (i = 0; i < AuPlink_NHASH; i++) {
+ hbl = sbinfo->si_plink + i;
+ if (!warned && verbose && !hlist_bl_empty(hbl)) {
+ pr_warn("pseudo-link is not flushed");
+ warned = 1;
+ }
+ hlist_bl_for_each_entry_safe(icntnr, pos, tmp, hbl, plink)
+ iput(&icntnr->vfs_inode);
+ INIT_HLIST_BL_HEAD(hbl);
+ }
+}
+
+void au_plink_clean(struct super_block *sb, int verbose)
+{
+ struct dentry *root;
+
+ root = sb->s_root;
+ aufs_write_lock(root);
+ if (au_opt_test(au_mntflags(sb), PLINK))
+ au_plink_put(sb, verbose);
+ aufs_write_unlock(root);
+}
+
+static int au_plink_do_half_refresh(struct inode *inode, aufs_bindex_t br_id)
+{
+ int do_put;
+ aufs_bindex_t btop, bbot, bindex;
+
+ do_put = 0;
+ btop = au_ibtop(inode);
+ bbot = au_ibbot(inode);
+ if (btop >= 0) {
+ for (bindex = btop; bindex <= bbot; bindex++) {
+ if (!au_h_iptr(inode, bindex)
+ || au_ii_br_id(inode, bindex) != br_id)
+ continue;
+ au_set_h_iptr(inode, bindex, NULL, 0);
+ do_put = 1;
+ break;
+ }
+ if (do_put)
+ for (bindex = btop; bindex <= bbot; bindex++)
+ if (au_h_iptr(inode, bindex)) {
+ do_put = 0;
+ break;
+ }
+ } else
+ do_put = 1;
+
+ return do_put;
+}
+
+/* free the plinks on a branch specified by @br_id */
+void au_plink_half_refresh(struct super_block *sb, aufs_bindex_t br_id)
+{
+ struct au_sbinfo *sbinfo;
+ struct hlist_bl_head *hbl;
+ struct hlist_bl_node *pos, *tmp;
+ struct au_icntnr *icntnr;
+ struct inode *inode;
+ int i, do_put;
+
+ SiMustWriteLock(sb);
+
+ sbinfo = au_sbi(sb);
+ AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+ AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
+
+ /* no bit_lock since sbinfo is write-locked */
+ for (i = 0; i < AuPlink_NHASH; i++) {
+ hbl = sbinfo->si_plink + i;
+ hlist_bl_for_each_entry_safe(icntnr, pos, tmp, hbl, plink) {
+ inode = au_igrab(&icntnr->vfs_inode);
+ ii_write_lock_child(inode);
+ do_put = au_plink_do_half_refresh(inode, br_id);
+ if (do_put) {
+ hlist_bl_del(&icntnr->plink);
+ iput(inode);
+ }
+ ii_write_unlock(inode);
+ iput(inode);
+ }
+ }
+}
generated by cgit 1.2.3-korg (git 2.39.0) at 2024-04-28 18:32:59 +0000