[PATCH] ext3_get_blocks: Adjust reservation window size for mblocks
Optimize the block reservation and the multiple block allocation: with the knowledge of the total number of blocks ahead, set or adjust the reservation window size properly (based on the number of blocks needed) before block allocation happens: if there isn't any reservation yet, make sure the reservation window equals to or greater than the number of blocks needed, before create an reservation window; if a reservation window is already exists, try to extends the window size to match the number of blocks to allocate. This could increase the possibility of completing multiple blocks allocation in a single request, as blocks are only allocated in the range of the inode's reservation window. Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -1011,6 +1011,31 @@ retry:
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goto retry;
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}
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static void try_to_extend_reservation(struct ext3_reserve_window_node *my_rsv,
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struct super_block *sb, int size)
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{
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struct ext3_reserve_window_node *next_rsv;
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struct rb_node *next;
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spinlock_t *rsv_lock = &EXT3_SB(sb)->s_rsv_window_lock;
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if (!spin_trylock(rsv_lock))
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return;
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next = rb_next(&my_rsv->rsv_node);
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if (!next)
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my_rsv->rsv_end += size;
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else {
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next_rsv = list_entry(next, struct ext3_reserve_window_node, rsv_node);
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if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
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my_rsv->rsv_end += size;
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else
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my_rsv->rsv_end = next_rsv->rsv_start - 1;
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}
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spin_unlock(rsv_lock);
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}
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/*
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* This is the main function used to allocate a new block and its reservation
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* window.
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@ -1095,6 +1120,8 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
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while (1) {
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if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
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!goal_in_my_reservation(&my_rsv->rsv_window, goal, group, sb)) {
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if (my_rsv->rsv_goal_size < *count)
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my_rsv->rsv_goal_size = *count;
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ret = alloc_new_reservation(my_rsv, goal, sb,
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group, bitmap_bh);
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if (ret < 0)
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@ -1102,7 +1129,10 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
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if (!goal_in_my_reservation(&my_rsv->rsv_window, goal, group, sb))
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goal = -1;
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}
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} else if (goal > 0 && (my_rsv->rsv_end-goal+1) < *count)
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try_to_extend_reservation(my_rsv, sb,
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*count-my_rsv->rsv_end + goal - 1);
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if ((my_rsv->rsv_start >= group_first_block + EXT3_BLOCKS_PER_GROUP(sb))
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|| (my_rsv->rsv_end < group_first_block))
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BUG();
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