[Aufs 14/25] aufs pseudo-link

J. R. Okajima
2009-03-09T03:35:42Z

pseudo-link is a logical hardlink over branches or different filesystems.

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
---
fs/aufs/plink.c | 335 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 335 insertions(+), 0 deletions(-)
create mode 100644 fs/aufs/plink.c

diff --git a/fs/aufs/plink.c b/fs/aufs/plink.c
new file mode 100644
index 0000000..62d258f
--- /dev/null
+++ b/fs/aufs/plink.c
@@ -0,0 +1,335 @@
+/*
+ * Copyright (C) 2005-2009 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.
+ */
+
+/*
+ * pseudo-link
+ */
+
+#include "aufs.h"
+
+/*
+ * during a user process maintains the pseudo-links,
+ * prohibit adding a new plink and branch manipulation.
+ */
+void au_plink_block_maintain(struct super_block *sb)
+{
+ struct au_sbinfo *sbi = au_sbi(sb);
+ /* gave up wake_up_bit() */
+ wait_event(sbi->si_plink_wq, !au_ftest_si(sbi, MAINTAIN_PLINK));
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct pseudo_link {
+ struct list_head list;
+ struct inode *inode;
+};
+
+#ifdef CONFIG_AUFS_DEBUG
+void au_plink_list(struct super_block *sb)
+{
+ struct au_sbinfo *sbinfo;
+ struct list_head *plink_list;
+ struct pseudo_link *plink;
+
+ sbinfo = au_sbi(sb);
+ AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+
+ plink_list = &sbinfo->si_plink.head;
+ spin_lock(&sbinfo->si_plink.spin);
+ list_for_each_entry(plink, plink_list, list)
+ AuDbg("%lu\n", plink->inode->i_ino);
+ spin_unlock(&sbinfo->si_plink.spin);
+}
+#endif
+
+/* is the inode pseudo-linked? */
+int au_plink_test(struct inode *inode)
+{
+ int found;
+ struct au_sbinfo *sbinfo;
+ struct list_head *plink_list;
+ struct pseudo_link *plink;
+
+ sbinfo = au_sbi(inode->i_sb);
+ AuDebugOn(!au_opt_test(au_mntflags(inode->i_sb), PLINK));
+
+ found = 0;
+ plink_list = &sbinfo->si_plink.head;
+ spin_lock(&sbinfo->si_plink.spin);
+ list_for_each_entry(plink, plink_list, list)
+ if (plink->inode == inode) {
+ found = 1;
+ break;
+ }
+ spin_unlock(&sbinfo->si_plink.spin);
+ 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;
+}
+
+/* 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;
+ struct inode *h_dir;
+ char a[PLINK_NAME_LEN];
+ struct qstr tgtname = {
+ .name = a
+ };
+
+ br = au_sbr(inode->i_sb, bindex);
+ h_parent = br->br_wbr->wbr_plink;
+ h_dir = h_parent->d_inode;
+ tgtname.len = plink_name(a, sizeof(a), inode, bindex);
+
+ /* always superio. */
+ mutex_lock_nested(&h_dir->i_mutex, AuLsc_I_CHILD2);
+ h_dentry = au_sio_lkup_one(&tgtname, h_parent, br);
+ mutex_unlock(&h_dir->i_mutex);
+ 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 = br->br_mnt
+ };
+ struct inode *h_dir;
+
+ h_dir = h_parent->d_inode;
+ again:
+ h_path.dentry = au_lkup_one(tgt, h_parent, br, /*nd*/NULL);
+ err = PTR_ERR(h_path.dentry);
+ if (IS_ERR(h_path.dentry))
+ goto out;
+
+ err = 0;
+ /* wh.plink dir is not monitored */
+ if (h_path.dentry->d_inode
+ && h_path.dentry->d_inode != h_dentry->d_inode) {
+ err = vfsub_unlink(h_dir, &h_path, /*force*/0);
+ dput(h_path.dentry);
+ h_path.dentry = NULL;
+ if (!err)
+ goto again;
+ }
+ if (!err && !h_path.dentry->d_inode)
+ err = vfsub_link(h_dentry, h_dir, &h_path);
+ dput(h_path.dentry);
+
+ out:
+ 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;
+ struct inode *h_dir;
+ char a[PLINK_NAME_LEN];
+ struct qstr tgtname = {
+ .name = a
+ };
+
+ wbr = au_sbr(inode->i_sb, bindex)->br_wbr;
+ h_parent = wbr->wbr_plink;
+ h_dir = h_parent->d_inode;
+ tgtname.len = plink_name(a, sizeof(a), inode, bindex);
+
+ /* always superio. */
+ mutex_lock_nested(&h_dir->i_mutex, AuLsc_I_CHILD2);
+ if (!au_test_wkq(current)) {
+ 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);
+ mutex_unlock(&h_dir->i_mutex);
+
+ return err;
+}
+
+/* free a single plink */
+static void do_put_plink(struct pseudo_link *plink, int do_del)
+{
+ iput(plink->inode);
+ if (do_del)
+ list_del(&plink->list);
+ kfree(plink);
+}
+
+/*
+ * 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 list_head *plink_list;
+ struct pseudo_link *plink;
+ int found, err, cnt;
+
+ sb = inode->i_sb;
+ sbinfo = au_sbi(sb);
+ AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+
+ err = 0;
+ cnt = 0;
+ found = 0;
+ plink_list = &sbinfo->si_plink.head;
+ spin_lock(&sbinfo->si_plink.spin);
+ list_for_each_entry(plink, plink_list, list) {
+ cnt++;
+ if (plink->inode == inode) {
+ found = 1;
+ break;
+ }
+ }
+ if (found) {
+ spin_unlock(&sbinfo->si_plink.spin);
+ return;
+ }
+
+ plink = NULL;
+ if (!found) {
+ plink = kmalloc(sizeof(*plink), GFP_ATOMIC);
+ if (plink) {
+ plink->inode = au_igrab(inode);
+ list_add(&plink->list, plink_list);
+ cnt++;
+ } else
+ err = -ENOMEM;
+ }
+ spin_unlock(&sbinfo->si_plink.spin);
+
+ if (!err) {
+ au_plink_block_maintain(sb);
+ err = whplink(h_dentry, inode, bindex, au_sbr(sb, bindex));
+ }
+
+ if (unlikely(cnt > AUFS_PLINK_WARN))
+ AuWarn1("unexpectedly many pseudo links, %d\n", cnt);
+ if (unlikely(err)) {
+ AuWarn("err %d, damaged pseudo link.\n", err);
+ if (!found && plink)
+ do_put_plink(plink, /*do_del*/1);
+ }
+}
+
+/* free all plinks */
+void au_plink_put(struct super_block *sb)
+{
+ struct au_sbinfo *sbinfo;
+ struct list_head *plink_list;
+ struct pseudo_link *plink, *tmp;
+
+ sbinfo = au_sbi(sb);
+ AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+
+ plink_list = &sbinfo->si_plink.head;
+ /* no spin_lock since sbinfo is write-locked */
+ list_for_each_entry_safe(plink, tmp, plink_list, list)
+ do_put_plink(plink, 0);
+ INIT_LIST_HEAD(plink_list);
+}
+
+/* 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 list_head *plink_list;
+ struct pseudo_link *plink, *tmp;
+ struct inode *inode;
+ aufs_bindex_t bstart, bend, bindex;
+ unsigned char do_put;
+
+ sbinfo = au_sbi(sb);
+ AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+
+ plink_list = &sbinfo->si_plink.head;
+ /* no spin_lock since sbinfo is write-locked */
+ list_for_each_entry_safe(plink, tmp, plink_list, list) {
+ do_put = 0;
+ inode = au_igrab(plink->inode);
+ ii_write_lock_child(inode);
+ bstart = au_ibstart(inode);
+ bend = au_ibend(inode);
+ if (bstart >= 0) {
+ for (bindex = bstart; bindex <= bend; 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;
+ }
+ } else
+ do_put_plink(plink, 1);
+
+ if (do_put) {
+ for (bindex = bstart; bindex <= bend; bindex++)
+ if (au_h_iptr(inode, bindex)) {
+ do_put = 0;
+ break;
+ }
+ if (do_put)
+ do_put_plink(plink, 1);
+ }
+ ii_write_unlock(inode);
+ iput(inode);
+ }
+}
--
1.6.1.284.g5dc13