[Aufs 15/25] aufs policies to select one among multiple writable branches

J. R. Okajima
2009-03-09T03:35:59Z

when creating/removing an entry and there are multiple writable branches
specified in aufs, aufs has to decide which branch is the target.
aufs has several policies for that such as, round-robin, most-free-space
and so on.

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
---
fs/aufs/wbr_policy.c | 628 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 628 insertions(+), 0 deletions(-)
create mode 100644 fs/aufs/wbr_policy.c

diff --git a/fs/aufs/wbr_policy.c b/fs/aufs/wbr_policy.c
new file mode 100644
index 0000000..436ebfc
--- /dev/null
+++ b/fs/aufs/wbr_policy.c
@@ -0,0 +1,628 @@
+/*
+ * 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.
+ */
+
+/*
+ * policies for selecting one among multiple writable branches
+ */
+
+#include <linux/statfs.h>
+#include "aufs.h"
+
+/* subset of cpup_attr() */
+static noinline_for_stack
+int au_cpdown_attr(struct path *h_path, struct dentry *h_src)
+{
+ int err, sbits;
+ struct iattr ia;
+ struct inode *h_isrc;
+
+ h_isrc = h_src->d_inode;
+ ia.ia_valid = ATTR_FORCE | ATTR_MODE | ATTR_UID | ATTR_GID;
+ ia.ia_mode = h_isrc->i_mode;
+ ia.ia_uid = h_isrc->i_uid;
+ ia.ia_gid = h_isrc->i_gid;
+ sbits = !!(ia.ia_mode & (S_ISUID | S_ISGID));
+ au_cpup_attr_flags(h_path->dentry->d_inode, h_isrc);
+ err = vfsub_sio_notify_change(h_path, &ia);
+
+ /* is this nfs only? */
+ if (!err && sbits && au_test_nfs(h_path->dentry->d_sb)) {
+ ia.ia_valid = ATTR_FORCE | ATTR_MODE;
+ ia.ia_mode = h_isrc->i_mode;
+ err = vfsub_sio_notify_change(h_path, &ia);
+ }
+
+ return err;
+}
+
+#define AuCpdown_PARENT_OPQ 1
+#define AuCpdown_WHED (1 << 1)
+#define AuCpdown_MADE_DIR (1 << 2)
+#define AuCpdown_DIROPQ (1 << 3)
+#define au_ftest_cpdown(flags, name) ((flags) & AuCpdown_##name)
+#define au_fset_cpdown(flags, name) { (flags) |= AuCpdown_##name; }
+#define au_fclr_cpdown(flags, name) { (flags) &= ~AuCpdown_##name; }
+
+struct au_cpdown_dir_args {
+ struct dentry *parent;
+ unsigned int flags;
+};
+
+static int au_cpdown_dir_opq(struct dentry *dentry, aufs_bindex_t bdst,
+ struct au_cpdown_dir_args *a)
+{
+ int err;
+ struct dentry *opq_dentry;
+
+ opq_dentry = au_diropq_create(dentry, bdst);
+ err = PTR_ERR(opq_dentry);
+ if (IS_ERR(opq_dentry))
+ goto out;
+ dput(opq_dentry);
+ au_fset_cpdown(a->flags, DIROPQ);
+
+ out:
+ return err;
+}
+
+static int au_cpdown_dir_wh(struct dentry *dentry, struct dentry *h_parent,
+ struct inode *dir, aufs_bindex_t bdst)
+{
+ int err;
+ struct path h_path;
+ struct au_branch *br;
+
+ br = au_sbr(dentry->d_sb, bdst);
+ h_path.dentry = au_wh_lkup(h_parent, &dentry->d_name, br);
+ err = PTR_ERR(h_path.dentry);
+ if (IS_ERR(h_path.dentry))
+ goto out;
+
+ err = 0;
+ if (h_path.dentry->d_inode) {
+ h_path.mnt = br->br_mnt;
+ err = au_wh_unlink_dentry(au_h_iptr(dir, bdst), &h_path,
+ dentry);
+ }
+ dput(h_path.dentry);
+
+ out:
+ return err;
+}
+
+static int au_cpdown_dir(struct dentry *dentry, aufs_bindex_t bdst,
+ struct dentry *h_parent, void *arg)
+{
+ int err, rerr;
+ aufs_bindex_t bend, bopq, bstart;
+ unsigned char parent_opq;
+ struct path h_path;
+ struct dentry *parent;
+ struct inode *h_dir, *h_inode, *inode, *dir;
+ struct au_cpdown_dir_args *args = arg;
+
+ bstart = au_dbstart(dentry);
+ /* dentry is di-locked */
+ parent = dget_parent(dentry);
+ dir = parent->d_inode;
+ h_dir = h_parent->d_inode;
+ AuDebugOn(h_dir != au_h_iptr(dir, bdst));
+ IMustLock(h_dir);
+
+ err = au_lkup_neg(dentry, bdst);
+ if (unlikely(err < 0))
+ goto out;
+ h_path.dentry = au_h_dptr(dentry, bdst);
+ h_path.mnt = au_sbr_mnt(dentry->d_sb, bdst);
+ err = vfsub_sio_mkdir(au_h_iptr(dir, bdst), &h_path,
+ S_IRWXU | S_IRUGO | S_IXUGO);
+ if (unlikely(err))
+ goto out_put;
+ au_fset_cpdown(args->flags, MADE_DIR);
+
+ bend = au_dbend(dentry);
+ bopq = au_dbdiropq(dentry);
+ au_fclr_cpdown(args->flags, WHED);
+ au_fclr_cpdown(args->flags, DIROPQ);
+ if (au_dbwh(dentry) == bdst)
+ au_fset_cpdown(args->flags, WHED);
+ if (!au_ftest_cpdown(args->flags, PARENT_OPQ) && bopq <= bdst)
+ au_fset_cpdown(args->flags, PARENT_OPQ);
+ parent_opq = (au_ftest_cpdown(args->flags, PARENT_OPQ)
+ && args->parent == dentry);
+ h_inode = h_path.dentry->d_inode;
+ mutex_lock_nested(&h_inode->i_mutex, AuLsc_I_CHILD);
+ if (au_ftest_cpdown(args->flags, WHED)) {
+ err = au_cpdown_dir_opq(dentry, bdst, args);
+ if (unlikely(err)) {
+ mutex_unlock(&h_inode->i_mutex);
+ goto out_dir;
+ }
+ }
+
+ err = au_cpdown_attr(&h_path, au_h_dptr(dentry, bstart));
+ mutex_unlock(&h_inode->i_mutex);
+ if (unlikely(err))
+ goto out_opq;
+
+ if (au_ftest_cpdown(args->flags, WHED)) {
+ err = au_cpdown_dir_wh(dentry, h_parent, dir, bdst);
+ if (unlikely(err))
+ goto out_opq;
+ }
+
+ inode = dentry->d_inode;
+ if (au_ibend(inode) < bdst)
+ au_set_ibend(inode, bdst);
+ au_set_h_iptr(inode, bdst, au_igrab(h_inode),
+ au_hi_flags(inode, /*isdir*/1));
+ goto out; /* success */
+
+ /* revert */
+ out_opq:
+ if (au_ftest_cpdown(args->flags, DIROPQ)) {
+ mutex_lock_nested(&h_inode->i_mutex, AuLsc_I_CHILD);
+ rerr = au_diropq_remove(dentry, bdst);
+ mutex_unlock(&h_inode->i_mutex);
+ if (unlikely(rerr)) {
+ AuIOErr("failed removing diropq for %.*s b%d (%d)\n",
+ AuDLNPair(dentry), bdst, rerr);
+ err = -EIO;
+ goto out;
+ }
+ }
+ out_dir:
+ if (au_ftest_cpdown(args->flags, MADE_DIR)) {
+ rerr = vfsub_sio_rmdir(au_h_iptr(dir, bdst), &h_path);
+ if (unlikely(rerr)) {
+ AuIOErr("failed removing %.*s b%d (%d)\n",
+ AuDLNPair(dentry), bdst, rerr);
+ err = -EIO;
+ }
+ }
+ out_put:
+ au_set_h_dptr(dentry, bdst, NULL);
+ if (au_dbend(dentry) == bdst)
+ au_update_dbend(dentry);
+ out:
+ dput(parent);
+ return err;
+}
+
+int au_cpdown_dirs(struct dentry *dentry, aufs_bindex_t bdst)
+{
+ int err;
+ struct au_cpdown_dir_args args = {
+ .parent = dget_parent(dentry),
+ .flags = 0
+ };
+
+ err = au_cp_dirs(dentry, bdst, au_cpdown_dir, &args);
+ dput(args.parent);
+
+ return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* policies for create */
+
+static int au_wbr_bu(struct super_block *sb, aufs_bindex_t bindex)
+{
+ for (; bindex >= 0; bindex--)
+ if (!au_br_rdonly(au_sbr(sb, bindex)))
+ return bindex;
+ return -EROFS;
+}
+
+/* top down parent */
+static int au_wbr_create_tdp(struct dentry *dentry, int isdir __maybe_unused)
+{
+ int err;
+ aufs_bindex_t bstart, bindex;
+ struct super_block *sb;
+ struct dentry *parent, *h_parent;
+
+ sb = dentry->d_sb;
+ bstart = au_dbstart(dentry);
+ err = bstart;
+ if (!au_br_rdonly(au_sbr(sb, bstart)))
+ goto out;
+
+ err = -EROFS;
+ parent = dget_parent(dentry);
+ for (bindex = au_dbstart(parent); bindex < bstart; bindex++) {
+ h_parent = au_h_dptr(parent, bindex);
+ if (!h_parent || !h_parent->d_inode)
+ continue;
+
+ if (!au_br_rdonly(au_sbr(sb, bindex))) {
+ err = bindex;
+ break;
+ }
+ }
+ dput(parent);
+
+ /* bottom up here */
+ if (unlikely(err < 0))
+ err = au_wbr_bu(sb, bstart - 1);
+
+ out:
+ AuDbg("b%d\n", err);
+ return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* an exception for the policy other than tdp */
+static int au_wbr_create_exp(struct dentry *dentry)
+{
+ int err;
+ aufs_bindex_t bwh, bdiropq;
+ struct dentry *parent;
+
+ err = -1;
+ bwh = au_dbwh(dentry);
+ parent = dget_parent(dentry);
+ bdiropq = au_dbdiropq(parent);
+ if (bwh >= 0) {
+ if (bdiropq >= 0)
+ err = min(bdiropq, bwh);
+ else
+ err = bwh;
+ AuDbg("%d\n", err);
+ } else if (bdiropq >= 0) {
+ err = bdiropq;
+ AuDbg("%d\n", err);
+ }
+ dput(parent);
+
+ if (err >= 0 && au_br_rdonly(au_sbr(dentry->d_sb, err)))
+ err = -1;
+
+ AuDbg("%d\n", err);
+ return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* round robin */
+static int au_wbr_create_init_rr(struct super_block *sb)
+{
+ int err;
+
+ err = au_wbr_bu(sb, au_sbend(sb));
+ atomic_set(&au_sbi(sb)->si_wbr_rr_next, -err); /* less important */
+
+ AuDbg("b%d\n", err);
+ return err;
+}
+
+static int au_wbr_create_rr(struct dentry *dentry, int isdir)
+{
+ int err, nbr;
+ unsigned int u;
+ aufs_bindex_t bindex, bend;
+ struct super_block *sb;
+ atomic_t *next;
+
+ err = au_wbr_create_exp(dentry);
+ if (err >= 0)
+ goto out;
+
+ sb = dentry->d_sb;
+ next = &au_sbi(sb)->si_wbr_rr_next;
+ bend = au_sbend(sb);
+ nbr = bend + 1;
+ for (bindex = 0; bindex <= bend; bindex++) {
+ if (!isdir) {
+ err = atomic_dec_return(next) + 1;
+ /* modulo for 0 is meaningless */
+ if (unlikely(!err))
+ err = atomic_dec_return(next) + 1;
+ } else
+ err = atomic_read(next);
+ AuDbg("%d\n", err);
+ u = err;
+ err = u % nbr;
+ AuDbg("%d\n", err);
+ if (!au_br_rdonly(au_sbr(sb, err)))
+ break;
+ err = -EROFS;
+ }
+
+ out:
+ AuDbg("%d\n", err);
+ return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* most free space */
+static void au_mfs(struct dentry *dentry)
+{
+ struct super_block *sb;
+ struct au_branch *br;
+ struct au_wbr_mfs *mfs;
+ aufs_bindex_t bindex, bend;
+ int err;
+ unsigned long long b, bavail;
+ /* reduce the stack usage */
+ struct kstatfs *st;
+
+ st = kmalloc(sizeof(*st), GFP_NOFS);
+ if (unlikely(!st)) {
+ AuWarn1("failed updating mfs(%d), ignored\n", -ENOMEM);
+ return;
+ }
+
+ bavail = 0;
+ sb = dentry->d_sb;
+ mfs = &au_sbi(sb)->si_wbr_mfs;
+ mfs->mfs_bindex = -EROFS;
+ mfs->mfsrr_bytes = 0;
+ bend = au_sbend(sb);
+ for (bindex = 0; bindex <= bend; bindex++) {
+ br = au_sbr(sb, bindex);
+ if (au_br_rdonly(br))
+ continue;
+
+ /* sb->s_root for NFS is unreliable */
+ err = vfs_statfs(br->br_mnt->mnt_root, st);
+ if (unlikely(err)) {
+ AuWarn1("failed statfs, b%d, %d\n", bindex, err);
+ continue;
+ }
+
+ /* when the available size is equal, select the lower one */
+ BUILD_BUG_ON(sizeof(b) < sizeof(st->f_bavail)
+ || sizeof(b) < sizeof(st->f_bsize));
+ b = st->f_bavail * st->f_bsize;
+ br->br_wbr->wbr_bytes = b;
+ if (b >= bavail) {
+ bavail = b;
+ mfs->mfs_bindex = bindex;
+ mfs->mfs_jiffy = jiffies;
+ }
+ }
+
+ mfs->mfsrr_bytes = bavail;
+ AuDbg("b%d\n", mfs->mfs_bindex);
+ kfree(st);
+}
+
+static int au_wbr_create_mfs(struct dentry *dentry, int isdir __maybe_unused)
+{
+ int err;
+ struct super_block *sb;
+ struct au_wbr_mfs *mfs;
+
+ err = au_wbr_create_exp(dentry);
+ if (err >= 0)
+ goto out;
+
+ sb = dentry->d_sb;
+ mfs = &au_sbi(sb)->si_wbr_mfs;
+ mutex_lock(&mfs->mfs_lock);
+ if (time_after(jiffies, mfs->mfs_jiffy + mfs->mfs_expire)
+ || mfs->mfs_bindex < 0
+ || au_br_rdonly(au_sbr(sb, mfs->mfs_bindex)))
+ au_mfs(dentry);
+ mutex_unlock(&mfs->mfs_lock);
+ err = mfs->mfs_bindex;
+
+ out:
+ AuDbg("b%d\n", err);
+ return err;
+}
+
+static int au_wbr_create_init_mfs(struct super_block *sb)
+{
+ struct au_wbr_mfs *mfs;
+
+ mfs = &au_sbi(sb)->si_wbr_mfs;
+ mutex_init(&mfs->mfs_lock);
+ mfs->mfs_jiffy = 0;
+ mfs->mfs_bindex = -EROFS;
+
+ return 0;
+}
+
+static int au_wbr_create_fin_mfs(struct super_block *sb __maybe_unused)
+{
+ mutex_destroy(&au_sbi(sb)->si_wbr_mfs.mfs_lock);
+ return 0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* most free space and then round robin */
+static int au_wbr_create_mfsrr(struct dentry *dentry, int isdir)
+{
+ int err;
+ struct au_wbr_mfs *mfs;
+
+ err = au_wbr_create_mfs(dentry, isdir);
+ if (err >= 0) {
+ mfs = &au_sbi(dentry->d_sb)->si_wbr_mfs;
+ if (mfs->mfsrr_bytes < mfs->mfsrr_watermark)
+ err = au_wbr_create_rr(dentry, isdir);
+ }
+
+ AuDbg("b%d\n", err);
+ return err;
+}
+
+static int au_wbr_create_init_mfsrr(struct super_block *sb)
+{
+ int err;
+
+ au_wbr_create_init_mfs(sb); /* ignore */
+ err = au_wbr_create_init_rr(sb);
+
+ return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* top down parent and most free space */
+static int au_wbr_create_pmfs(struct dentry *dentry, int isdir)
+{
+ int err, e2;
+ unsigned long long b;
+ aufs_bindex_t bindex, bstart, bend;
+ struct super_block *sb;
+ struct dentry *parent, *h_parent;
+ struct au_branch *br;
+
+ err = au_wbr_create_tdp(dentry, isdir);
+ if (unlikely(err < 0))
+ goto out;
+ parent = dget_parent(dentry);
+ bstart = au_dbstart(parent);
+ bend = au_dbtaildir(parent);
+ if (bstart == bend)
+ goto out_parent; /* success */
+
+ e2 = au_wbr_create_mfs(dentry, isdir);
+ if (e2 < 0)
+ goto out_parent; /* success */
+
+ /* when the available size is equal, select upper one */
+ sb = dentry->d_sb;
+ br = au_sbr(sb, err);
+ b = br->br_wbr->wbr_bytes;
+ AuDbg("b%d, %llu\n", err, b);
+
+ for (bindex = bstart; bindex <= bend; bindex++) {
+ h_parent = au_h_dptr(parent, bindex);
+ if (!h_parent || !h_parent->d_inode)
+ continue;
+
+ br = au_sbr(sb, bindex);
+ if (!au_br_rdonly(br) && br->br_wbr->wbr_bytes > b) {
+ b = br->br_wbr->wbr_bytes;
+ err = bindex;
+ AuDbg("b%d, %llu\n", err, b);
+ }
+ }
+
+ out_parent:
+ dput(parent);
+ out:
+ AuDbg("b%d\n", err);
+ return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* policies for copyup */
+
+/* top down parent */
+static int au_wbr_copyup_tdp(struct dentry *dentry)
+{
+ return au_wbr_create_tdp(dentry, /*isdir, anything is ok*/0);
+}
+
+/* bottom up parent */
+static int au_wbr_copyup_bup(struct dentry *dentry)
+{
+ int err;
+ aufs_bindex_t bindex, bstart;
+ struct dentry *parent, *h_parent;
+ struct super_block *sb;
+
+ err = -EROFS;
+ sb = dentry->d_sb;
+ parent = dget_parent(dentry);
+ bstart = au_dbstart(parent);
+ for (bindex = au_dbstart(dentry); bindex >= bstart; bindex--) {
+ h_parent = au_h_dptr(parent, bindex);
+ if (!h_parent || !h_parent->d_inode)
+ continue;
+
+ if (!au_br_rdonly(au_sbr(sb, bindex))) {
+ err = bindex;
+ break;
+ }
+ }
+ dput(parent);
+
+ /* bottom up here */
+ if (unlikely(err < 0))
+ err = au_wbr_bu(sb, bstart - 1);
+
+ AuDbg("b%d\n", err);
+ return err;
+}
+
+/* bottom up */
+static int au_wbr_copyup_bu(struct dentry *dentry)
+{
+ int err;
+
+ err = au_wbr_bu(dentry->d_sb, au_dbstart(dentry));
+
+ AuDbg("b%d\n", err);
+ return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_wbr_copyup_operations au_wbr_copyup_ops[] = {
+ [AuWbrCopyup_TDP] = {
+ .copyup = au_wbr_copyup_tdp
+ },
+ [AuWbrCopyup_BUP] = {
+ .copyup = au_wbr_copyup_bup
+ },
+ [AuWbrCopyup_BU] = {
+ .copyup = au_wbr_copyup_bu
+ }
+};
+
+struct au_wbr_create_operations au_wbr_create_ops[] = {
+ [AuWbrCreate_TDP] = {
+ .create = au_wbr_create_tdp
+ },
+ [AuWbrCreate_RR] = {
+ .create = au_wbr_create_rr,
+ .init = au_wbr_create_init_rr
+ },
+ [AuWbrCreate_MFS] = {
+ .create = au_wbr_create_mfs,
+ .init = au_wbr_create_init_mfs,
+ .fin = au_wbr_create_fin_mfs
+ },
+ [AuWbrCreate_MFSV] = {
+ .create = au_wbr_create_mfs,
+ .init = au_wbr_create_init_mfs,
+ .fin = au_wbr_create_fin_mfs
+ },
+ [AuWbrCreate_MFSRR] = {
+ .create = au_wbr_create_mfsrr,
+ .init = au_wbr_create_init_mfsrr,
+ .fin = au_wbr_create_fin_mfs
+ },
+ [AuWbrCreate_MFSRRV] = {
+ .create = au_wbr_create_mfsrr,
+ .init = au_wbr_create_init_mfsrr,
+ .fin = au_wbr_create_fin_mfs
+ },
+ [AuWbrCreate_PMFS] = {
+ .create = au_wbr_create_pmfs,
+ .init = au_wbr_create_init_mfs,
+ .fin = au_wbr_create_fin_mfs
+ },
+ [AuWbrCreate_PMFSV] = {
+ .create = au_wbr_create_pmfs,
+ .init = au_wbr_create_init_mfs,
+ .fin = au_wbr_create_fin_mfs
+ }
+};
--
1.6.1.284.g5dc13