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    Subject[PATCH 04/17] fs: icache lock i_state
    Date
    From: Nick Piggin <npiggin@suse.de>

    We currently protect the per-inode state flags with the inode_lock.
    Using a global lock to protect per-object state is overkill when we
    coul duse a per-inode lock to protect the state. Use the
    inode->i_lock for this, and wrap all the state changes and checks
    with the inode->i_lock.

    Signed-off-by: Nick Piggin <npiggin@suse.de>
    Signed-off-by: Dave Chinner <dchinner@redhat.com>
    ---
    fs/drop_caches.c | 9 ++++--
    fs/fs-writeback.c | 29 +++++++++++++++--
    fs/inode.c | 86 +++++++++++++++++++++++++++++++++++++++++++++-------
    fs/nilfs2/gcdat.c | 1 +
    fs/quota/dquot.c | 12 ++++---
    5 files changed, 113 insertions(+), 24 deletions(-)

    diff --git a/fs/drop_caches.c b/fs/drop_caches.c
    index ab69ae7..45bdf88 100644
    --- a/fs/drop_caches.c
    +++ b/fs/drop_caches.c
    @@ -19,11 +19,14 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
    spin_lock(&inode_lock);
    spin_lock(&sb_inode_list_lock);
    list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
    - if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
    - continue;
    - if (inode->i_mapping->nrpages == 0)
    + spin_lock(&inode->i_lock);
    + if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)
    + || inode->i_mapping->nrpages == 0) {
    + spin_unlock(&inode->i_lock);
    continue;
    + }
    __iget(inode);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&sb_inode_list_lock);
    spin_unlock(&inode_lock);
    invalidate_mapping_pages(inode->i_mapping, 0, -1);
    diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
    index 9adc9d9..7bd1aef 100644
    --- a/fs/fs-writeback.c
    +++ b/fs/fs-writeback.c
    @@ -280,10 +280,12 @@ static void inode_wait_for_writeback(struct inode *inode)
    wait_queue_head_t *wqh;

    wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
    - while (inode->i_state & I_SYNC) {
    + while (inode->i_state & I_SYNC) {
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
    spin_lock(&inode_lock);
    + spin_lock(&inode->i_lock);
    }
    }

    @@ -337,6 +339,7 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
    /* Set I_SYNC, reset I_DIRTY_PAGES */
    inode->i_state |= I_SYNC;
    inode->i_state &= ~I_DIRTY_PAGES;
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);

    ret = do_writepages(mapping, wbc);
    @@ -358,8 +361,10 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
    * write_inode()
    */
    spin_lock(&inode_lock);
    + spin_lock(&inode->i_lock);
    dirty = inode->i_state & I_DIRTY;
    inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    /* Don't write the inode if only I_DIRTY_PAGES was set */
    if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
    @@ -369,6 +374,7 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
    }

    spin_lock(&inode_lock);
    + spin_lock(&inode->i_lock);
    inode->i_state &= ~I_SYNC;
    if (!(inode->i_state & I_FREEING)) {
    if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
    @@ -479,7 +485,9 @@ static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
    return 0;
    }

    + spin_lock(&inode->i_lock);
    if (inode->i_state & (I_NEW | I_WILL_FREE)) {
    + spin_unlock(&inode->i_lock);
    requeue_io(inode);
    continue;
    }
    @@ -487,8 +495,10 @@ static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
    * Was this inode dirtied after sync_sb_inodes was called?
    * This keeps sync from extra jobs and livelock.
    */
    - if (inode_dirtied_after(inode, wbc->wb_start))
    + if (inode_dirtied_after(inode, wbc->wb_start)) {
    + spin_unlock(&inode->i_lock);
    return 1;
    + }

    BUG_ON(inode->i_state & I_FREEING);
    __iget(inode);
    @@ -501,6 +511,7 @@ static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
    */
    redirty_tail(inode);
    }
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    iput(inode);
    cond_resched();
    @@ -936,6 +947,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
    block_dump___mark_inode_dirty(inode);

    spin_lock(&inode_lock);
    + spin_lock(&inode->i_lock);
    if ((inode->i_state & flags) != flags) {
    const int was_dirty = inode->i_state & I_DIRTY;

    @@ -986,6 +998,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
    }
    }
    out:
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);

    if (wakeup_bdi)
    @@ -1033,12 +1046,16 @@ static void wait_sb_inodes(struct super_block *sb)
    list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
    struct address_space *mapping;

    - if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
    - continue;
    mapping = inode->i_mapping;
    if (mapping->nrpages == 0)
    continue;
    + spin_lock(&inode->i_lock);
    + if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
    + spin_unlock(&inode->i_lock);
    + continue;
    + }
    __iget(inode);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&sb_inode_list_lock);
    spin_unlock(&inode_lock);
    /*
    @@ -1165,7 +1182,9 @@ int write_inode_now(struct inode *inode, int sync)

    might_sleep();
    spin_lock(&inode_lock);
    + spin_lock(&inode->i_lock);
    ret = writeback_single_inode(inode, &wbc);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    if (sync)
    inode_sync_wait(inode);
    @@ -1189,7 +1208,9 @@ int sync_inode(struct inode *inode, struct writeback_control *wbc)
    int ret;

    spin_lock(&inode_lock);
    + spin_lock(&inode->i_lock);
    ret = writeback_single_inode(inode, wbc);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    return ret;
    }
    diff --git a/fs/inode.c b/fs/inode.c
    index 9d7ffb1..906a4ad 100644
    --- a/fs/inode.c
    +++ b/fs/inode.c
    @@ -31,10 +31,13 @@
    * s_inodes, i_sb_list
    * inode_hash_lock protects:
    * inode hash table, i_hash
    + * inode->i_lock protects:
    + * i_state
    *
    * Ordering:
    * inode_lock
    * sb_inode_list_lock
    + * inode->i_lock
    * inode_lock
    * inode_hash_lock
    */
    @@ -296,6 +299,8 @@ static void init_once(void *foo)
    */
    void __iget(struct inode *inode)
    {
    + assert_spin_locked(&inode->i_lock);
    +
    if (atomic_inc_return(&inode->i_count) != 1)
    return;

    @@ -396,16 +401,21 @@ static int invalidate_list(struct list_head *head, struct list_head *dispose)
    if (tmp == head)
    break;
    inode = list_entry(tmp, struct inode, i_sb_list);
    - if (inode->i_state & I_NEW)
    + spin_lock(&inode->i_lock);
    + if (inode->i_state & I_NEW) {
    + spin_unlock(&inode->i_lock);
    continue;
    + }
    invalidate_inode_buffers(inode);
    if (!atomic_read(&inode->i_count)) {
    list_move(&inode->i_list, dispose);
    WARN_ON(inode->i_state & I_NEW);
    inode->i_state |= I_FREEING;
    + spin_unlock(&inode->i_lock);
    count++;
    continue;
    }
    + spin_unlock(&inode->i_lock);
    busy = 1;
    }
    /* only unused inodes may be cached with i_count zero */
    @@ -484,12 +494,15 @@ static void prune_icache(int nr_to_scan)

    inode = list_entry(inode_unused.prev, struct inode, i_list);

    + spin_lock(&inode->i_lock);
    if (inode->i_state || atomic_read(&inode->i_count)) {
    list_move(&inode->i_list, &inode_unused);
    + spin_unlock(&inode->i_lock);
    continue;
    }
    if (inode_has_buffers(inode) || inode->i_data.nrpages) {
    __iget(inode);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    if (remove_inode_buffers(inode))
    reap += invalidate_mapping_pages(&inode->i_data,
    @@ -500,12 +513,16 @@ static void prune_icache(int nr_to_scan)
    if (inode != list_entry(inode_unused.next,
    struct inode, i_list))
    continue; /* wrong inode or list_empty */
    - if (!can_unuse(inode))
    + spin_lock(&inode->i_lock);
    + if (!can_unuse(inode)) {
    + spin_unlock(&inode->i_lock);
    continue;
    + }
    }
    list_move(&inode->i_list, &freeable);
    WARN_ON(inode->i_state & I_NEW);
    inode->i_state |= I_FREEING;
    + spin_unlock(&inode->i_lock);
    nr_pruned++;
    }
    inodes_stat.nr_unused -= nr_pruned;
    @@ -568,8 +585,14 @@ repeat:
    hlist_for_each_entry(inode, node, head, i_hash) {
    if (inode->i_sb != sb)
    continue;
    - if (!test(inode, data))
    + if (!spin_trylock(&inode->i_lock)) {
    + spin_unlock(&inode_hash_lock);
    + goto repeat;
    + }
    + if (!test(inode, data)) {
    + spin_unlock(&inode->i_lock);
    continue;
    + }
    if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
    spin_unlock(&inode_hash_lock);
    __wait_on_freeing_inode(inode);
    @@ -598,6 +621,10 @@ repeat:
    continue;
    if (inode->i_sb != sb)
    continue;
    + if (!spin_trylock(&inode->i_lock)) {
    + spin_unlock(&inode_hash_lock);
    + goto repeat;
    + }
    if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
    spin_unlock(&inode_hash_lock);
    __wait_on_freeing_inode(inode);
    @@ -624,10 +651,10 @@ __inode_add_to_lists(struct super_block *sb, struct hlist_head *head,
    struct inode *inode)
    {
    inodes_stat.nr_inodes++;
    - list_add(&inode->i_list, &inode_in_use);
    spin_lock(&sb_inode_list_lock);
    list_add(&inode->i_sb_list, &sb->s_inodes);
    spin_unlock(&sb_inode_list_lock);
    + list_add(&inode->i_list, &inode_in_use);
    if (head) {
    spin_lock(&inode_hash_lock);
    hlist_add_head(&inode->i_hash, head);
    @@ -684,9 +711,9 @@ struct inode *new_inode(struct super_block *sb)
    inode = alloc_inode(sb);
    if (inode) {
    spin_lock(&inode_lock);
    - __inode_add_to_lists(sb, NULL, inode);
    inode->i_ino = ++last_ino;
    inode->i_state = 0;
    + __inode_add_to_lists(sb, NULL, inode);
    spin_unlock(&inode_lock);
    }
    return inode;
    @@ -753,8 +780,8 @@ static struct inode *get_new_inode(struct super_block *sb,
    if (set(inode, data))
    goto set_failed;

    - __inode_add_to_lists(sb, head, inode);
    inode->i_state = I_NEW;
    + __inode_add_to_lists(sb, head, inode);
    spin_unlock(&inode_lock);

    /* Return the locked inode with I_NEW set, the
    @@ -769,6 +796,7 @@ static struct inode *get_new_inode(struct super_block *sb,
    * allocated.
    */
    __iget(old);
    + spin_unlock(&old->i_lock);
    spin_unlock(&inode_lock);
    destroy_inode(inode);
    inode = old;
    @@ -777,6 +805,7 @@ static struct inode *get_new_inode(struct super_block *sb,
    return inode;

    set_failed:
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    destroy_inode(inode);
    return NULL;
    @@ -800,8 +829,8 @@ static struct inode *get_new_inode_fast(struct super_block *sb,
    old = find_inode_fast(sb, head, ino);
    if (!old) {
    inode->i_ino = ino;
    - __inode_add_to_lists(sb, head, inode);
    inode->i_state = I_NEW;
    + __inode_add_to_lists(sb, head, inode);
    spin_unlock(&inode_lock);

    /* Return the locked inode with I_NEW set, the
    @@ -816,6 +845,7 @@ static struct inode *get_new_inode_fast(struct super_block *sb,
    * allocated.
    */
    __iget(old);
    + spin_unlock(&old->i_lock);
    spin_unlock(&inode_lock);
    destroy_inode(inode);
    inode = old;
    @@ -857,6 +887,7 @@ ino_t iunique(struct super_block *sb, ino_t max_reserved)
    res = counter++;
    head = inode_hashtable + hash(sb, res);
    inode = find_inode_fast(sb, head, res);
    + spin_unlock(&inode->i_lock);
    } while (inode != NULL);
    spin_unlock(&inode_lock);

    @@ -866,18 +897,24 @@ EXPORT_SYMBOL(iunique);

    struct inode *igrab(struct inode *inode)
    {
    + struct inode *ret = inode;
    +
    spin_lock(&inode_lock);
    - if (!(inode->i_state & (I_FREEING|I_WILL_FREE)))
    + spin_lock(&inode->i_lock);
    + if (!(inode->i_state & (I_FREEING|I_WILL_FREE))) {
    __iget(inode);
    - else
    + } else {
    /*
    * Handle the case where s_op->clear_inode is not been
    * called yet, and somebody is calling igrab
    * while the inode is getting freed.
    */
    - inode = NULL;
    + ret = NULL;
    + }
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    - return inode;
    +
    + return ret;
    }
    EXPORT_SYMBOL(igrab);

    @@ -910,6 +947,7 @@ static struct inode *ifind(struct super_block *sb,
    inode = find_inode(sb, head, test, data);
    if (inode) {
    __iget(inode);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    if (likely(wait))
    wait_on_inode(inode);
    @@ -943,6 +981,7 @@ static struct inode *ifind_fast(struct super_block *sb,
    inode = find_inode_fast(sb, head, ino);
    if (inode) {
    __iget(inode);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    wait_on_inode(inode);
    return inode;
    @@ -1112,6 +1151,7 @@ int insert_inode_locked(struct inode *inode)
    struct inode *old = NULL;

    spin_lock(&inode_lock);
    +repeat:
    spin_lock(&inode_hash_lock);
    hlist_for_each_entry(old, node, head, i_hash) {
    if (old->i_ino != ino)
    @@ -1120,6 +1160,10 @@ int insert_inode_locked(struct inode *inode)
    continue;
    if (old->i_state & (I_FREEING|I_WILL_FREE))
    continue;
    + if (!spin_trylock(&old->i_lock)) {
    + spin_unlock(&inode_hash_lock);
    + goto repeat;
    + }
    break;
    }
    if (likely(!node)) {
    @@ -1130,6 +1174,7 @@ int insert_inode_locked(struct inode *inode)
    }
    spin_unlock(&inode_hash_lock);
    __iget(old);
    + spin_unlock(&old->i_lock);
    spin_unlock(&inode_lock);
    wait_on_inode(old);
    if (unlikely(!hlist_unhashed(&old->i_hash))) {
    @@ -1154,6 +1199,7 @@ int insert_inode_locked4(struct inode *inode, unsigned long hashval,
    struct inode *old = NULL;

    spin_lock(&inode_lock);
    +repeat:
    spin_lock(&inode_hash_lock);
    hlist_for_each_entry(old, node, head, i_hash) {
    if (old->i_sb != sb)
    @@ -1162,6 +1208,10 @@ int insert_inode_locked4(struct inode *inode, unsigned long hashval,
    continue;
    if (old->i_state & (I_FREEING|I_WILL_FREE))
    continue;
    + if (!spin_trylock(&old->i_lock)) {
    + spin_unlock(&inode_hash_lock);
    + goto repeat;
    + }
    break;
    }
    if (likely(!node)) {
    @@ -1172,6 +1222,7 @@ int insert_inode_locked4(struct inode *inode, unsigned long hashval,
    }
    spin_unlock(&inode_hash_lock);
    __iget(old);
    + spin_unlock(&old->i_lock);
    spin_unlock(&inode_lock);
    wait_on_inode(old);
    if (unlikely(!hlist_unhashed(&old->i_hash))) {
    @@ -1256,19 +1307,27 @@ static void iput_final(struct inode *inode)
    else
    drop = generic_drop_inode(inode);

    + spin_lock(&sb_inode_list_lock);
    + spin_lock(&inode->i_lock);
    if (!drop) {
    if (!(inode->i_state & (I_DIRTY|I_SYNC)))
    list_move(&inode->i_list, &inode_unused);
    inodes_stat.nr_unused++;
    if (sb->s_flags & MS_ACTIVE) {
    + spin_unlock(&inode->i_lock);
    + spin_unlock(&sb_inode_list_lock);
    spin_unlock(&inode_lock);
    return;
    }
    WARN_ON(inode->i_state & I_NEW);
    inode->i_state |= I_WILL_FREE;
    + spin_unlock(&inode->i_lock);
    + spin_unlock(&sb_inode_list_lock);
    spin_unlock(&inode_lock);
    write_inode_now(inode, 1);
    spin_lock(&inode_lock);
    + spin_lock(&sb_inode_list_lock);
    + spin_lock(&inode->i_lock);
    WARN_ON(inode->i_state & I_NEW);
    inode->i_state &= ~I_WILL_FREE;
    inodes_stat.nr_unused--;
    @@ -1277,12 +1336,12 @@ static void iput_final(struct inode *inode)
    spin_unlock(&inode_hash_lock);
    }
    list_del_init(&inode->i_list);
    - spin_lock(&sb_inode_list_lock);
    list_del_init(&inode->i_sb_list);
    spin_unlock(&sb_inode_list_lock);
    WARN_ON(inode->i_state & I_NEW);
    inode->i_state |= I_FREEING;
    inodes_stat.nr_inodes--;
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    evict(inode);
    spin_lock(&inode_lock);
    @@ -1491,6 +1550,8 @@ EXPORT_SYMBOL(inode_wait);
    * wake_up_inode() after removing from the hash list will DTRT.
    *
    * This is called with inode_lock held.
    + *
    + * Called with i_lock held and returns with it dropped.
    */
    static void __wait_on_freeing_inode(struct inode *inode)
    {
    @@ -1498,6 +1559,7 @@ static void __wait_on_freeing_inode(struct inode *inode)
    DEFINE_WAIT_BIT(wait, &inode->i_state, __I_NEW);
    wq = bit_waitqueue(&inode->i_state, __I_NEW);
    prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&inode_lock);
    schedule();
    finish_wait(wq, &wait.wait);
    diff --git a/fs/nilfs2/gcdat.c b/fs/nilfs2/gcdat.c
    index 84a45d1..c51f0e8 100644
    --- a/fs/nilfs2/gcdat.c
    +++ b/fs/nilfs2/gcdat.c
    @@ -27,6 +27,7 @@
    #include "page.h"
    #include "mdt.h"

    +/* XXX: what protects i_state? */
    int nilfs_init_gcdat_inode(struct the_nilfs *nilfs)
    {
    struct inode *dat = nilfs->ns_dat, *gcdat = nilfs->ns_gc_dat;
    diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
    index 2e3b913..15f66f1 100644
    --- a/fs/quota/dquot.c
    +++ b/fs/quota/dquot.c
    @@ -899,18 +899,20 @@ static void add_dquot_ref(struct super_block *sb, int type)
    spin_lock(&inode_lock);
    spin_lock(&sb_inode_list_lock);
    list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
    - if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
    + spin_lock(&inode->i_lock);
    + if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW) ||
    + !atomic_read(&inode->i_writecount) ||
    + !dqinit_needed(inode, type))) {
    + spin_unlock(&inode->i_lock);
    continue;
    + }
    #ifdef CONFIG_QUOTA_DEBUG
    if (unlikely(inode_get_rsv_space(inode) > 0))
    reserved = 1;
    #endif
    - if (!atomic_read(&inode->i_writecount))
    - continue;
    - if (!dqinit_needed(inode, type))
    - continue;

    __iget(inode);
    + spin_unlock(&inode->i_lock);
    spin_unlock(&sb_inode_list_lock);
    spin_unlock(&inode_lock);

    --
    1.7.1


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