forked from luck/tmp_suning_uos_patched
fdc0212e86
This commit adds two members in extent_status structure to let it record physical block and extent status. Here es_pblk is used to record both of them because physical block only has 48 bits. So extent status could be stashed into it so that we can save some memory. Now written, unwritten, delayed and hole are defined as status. Due to new member is added into extent status tree, all interfaces need to be adjusted. Signed-off-by: Zheng Liu <wenqing.lz@taobao.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz>
584 lines
16 KiB
C
584 lines
16 KiB
C
/*
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* fs/ext4/extents_status.c
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*
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* Written by Yongqiang Yang <xiaoqiangnk@gmail.com>
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* Modified by
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* Allison Henderson <achender@linux.vnet.ibm.com>
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* Hugh Dickins <hughd@google.com>
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* Zheng Liu <wenqing.lz@taobao.com>
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*
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* Ext4 extents status tree core functions.
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*/
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#include <linux/rbtree.h>
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#include "ext4.h"
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#include "extents_status.h"
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#include "ext4_extents.h"
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#include <trace/events/ext4.h>
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/*
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* According to previous discussion in Ext4 Developer Workshop, we
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* will introduce a new structure called io tree to track all extent
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* status in order to solve some problems that we have met
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* (e.g. Reservation space warning), and provide extent-level locking.
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* Delay extent tree is the first step to achieve this goal. It is
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* original built by Yongqiang Yang. At that time it is called delay
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* extent tree, whose goal is only track delayed extents in memory to
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* simplify the implementation of fiemap and bigalloc, and introduce
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* lseek SEEK_DATA/SEEK_HOLE support. That is why it is still called
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* delay extent tree at the first commit. But for better understand
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* what it does, it has been rename to extent status tree.
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*
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* Step1:
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* Currently the first step has been done. All delayed extents are
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* tracked in the tree. It maintains the delayed extent when a delayed
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* allocation is issued, and the delayed extent is written out or
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* invalidated. Therefore the implementation of fiemap and bigalloc
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* are simplified, and SEEK_DATA/SEEK_HOLE are introduced.
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*
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* The following comment describes the implemenmtation of extent
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* status tree and future works.
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*
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* Step2:
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* In this step all extent status are tracked by extent status tree.
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* Thus, we can first try to lookup a block mapping in this tree before
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* finding it in extent tree. Hence, single extent cache can be removed
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* because extent status tree can do a better job. Extents in status
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* tree are loaded on-demand. Therefore, the extent status tree may not
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* contain all of the extents in a file. Meanwhile we define a shrinker
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* to reclaim memory from extent status tree because fragmented extent
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* tree will make status tree cost too much memory. written/unwritten/-
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* hole extents in the tree will be reclaimed by this shrinker when we
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* are under high memory pressure. Delayed extents will not be
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* reclimed because fiemap, bigalloc, and seek_data/hole need it.
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*/
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/*
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* Extent status tree implementation for ext4.
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*
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*
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* ==========================================================================
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* Extent status tree tracks all extent status.
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*
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* 1. Why we need to implement extent status tree?
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*
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* Without extent status tree, ext4 identifies a delayed extent by looking
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* up page cache, this has several deficiencies - complicated, buggy,
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* and inefficient code.
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*
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* FIEMAP, SEEK_HOLE/DATA, bigalloc, and writeout all need to know if a
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* block or a range of blocks are belonged to a delayed extent.
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*
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* Let us have a look at how they do without extent status tree.
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* -- FIEMAP
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* FIEMAP looks up page cache to identify delayed allocations from holes.
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*
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* -- SEEK_HOLE/DATA
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* SEEK_HOLE/DATA has the same problem as FIEMAP.
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*
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* -- bigalloc
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* bigalloc looks up page cache to figure out if a block is
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* already under delayed allocation or not to determine whether
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* quota reserving is needed for the cluster.
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*
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* -- writeout
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* Writeout looks up whole page cache to see if a buffer is
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* mapped, If there are not very many delayed buffers, then it is
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* time comsuming.
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*
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* With extent status tree implementation, FIEMAP, SEEK_HOLE/DATA,
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* bigalloc and writeout can figure out if a block or a range of
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* blocks is under delayed allocation(belonged to a delayed extent) or
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* not by searching the extent tree.
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*
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*
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* ==========================================================================
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* 2. Ext4 extent status tree impelmentation
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*
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* -- extent
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* A extent is a range of blocks which are contiguous logically and
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* physically. Unlike extent in extent tree, this extent in ext4 is
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* a in-memory struct, there is no corresponding on-disk data. There
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* is no limit on length of extent, so an extent can contain as many
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* blocks as they are contiguous logically and physically.
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*
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* -- extent status tree
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* Every inode has an extent status tree and all allocation blocks
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* are added to the tree with different status. The extent in the
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* tree are ordered by logical block no.
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*
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* -- operations on a extent status tree
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* There are three important operations on a delayed extent tree: find
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* next extent, adding a extent(a range of blocks) and removing a extent.
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*
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* -- race on a extent status tree
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* Extent status tree is protected by inode->i_es_lock.
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*
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* -- memory consumption
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* Fragmented extent tree will make extent status tree cost too much
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* memory. Hence, we will reclaim written/unwritten/hole extents from
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* the tree under a heavy memory pressure.
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*
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*
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* ==========================================================================
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* 3. Performance analysis
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*
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* -- overhead
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* 1. There is a cache extent for write access, so if writes are
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* not very random, adding space operaions are in O(1) time.
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*
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* -- gain
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* 2. Code is much simpler, more readable, more maintainable and
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* more efficient.
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*
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*
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* ==========================================================================
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* 4. TODO list
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*
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* -- Refactor delayed space reservation
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*
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* -- Extent-level locking
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*/
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static struct kmem_cache *ext4_es_cachep;
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static int __es_insert_extent(struct ext4_es_tree *tree,
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struct extent_status *newes);
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static int __es_remove_extent(struct ext4_es_tree *tree, ext4_lblk_t lblk,
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ext4_lblk_t end);
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int __init ext4_init_es(void)
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{
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ext4_es_cachep = KMEM_CACHE(extent_status, SLAB_RECLAIM_ACCOUNT);
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if (ext4_es_cachep == NULL)
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return -ENOMEM;
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return 0;
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}
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void ext4_exit_es(void)
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{
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if (ext4_es_cachep)
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kmem_cache_destroy(ext4_es_cachep);
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}
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void ext4_es_init_tree(struct ext4_es_tree *tree)
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{
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tree->root = RB_ROOT;
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tree->cache_es = NULL;
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}
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#ifdef ES_DEBUG__
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static void ext4_es_print_tree(struct inode *inode)
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{
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struct ext4_es_tree *tree;
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struct rb_node *node;
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printk(KERN_DEBUG "status extents for inode %lu:", inode->i_ino);
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tree = &EXT4_I(inode)->i_es_tree;
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node = rb_first(&tree->root);
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while (node) {
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struct extent_status *es;
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es = rb_entry(node, struct extent_status, rb_node);
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printk(KERN_DEBUG " [%u/%u) %llu %llx",
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es->es_lblk, es->es_len,
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ext4_es_pblock(es), ext4_es_status(es));
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node = rb_next(node);
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}
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printk(KERN_DEBUG "\n");
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}
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#else
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#define ext4_es_print_tree(inode)
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#endif
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static inline ext4_lblk_t ext4_es_end(struct extent_status *es)
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{
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BUG_ON(es->es_lblk + es->es_len < es->es_lblk);
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return es->es_lblk + es->es_len - 1;
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}
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/*
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* search through the tree for an delayed extent with a given offset. If
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* it can't be found, try to find next extent.
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*/
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static struct extent_status *__es_tree_search(struct rb_root *root,
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ext4_lblk_t lblk)
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{
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struct rb_node *node = root->rb_node;
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struct extent_status *es = NULL;
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while (node) {
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es = rb_entry(node, struct extent_status, rb_node);
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if (lblk < es->es_lblk)
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node = node->rb_left;
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else if (lblk > ext4_es_end(es))
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node = node->rb_right;
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else
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return es;
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}
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if (es && lblk < es->es_lblk)
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return es;
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if (es && lblk > ext4_es_end(es)) {
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node = rb_next(&es->rb_node);
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return node ? rb_entry(node, struct extent_status, rb_node) :
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NULL;
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}
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return NULL;
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}
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/*
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* ext4_es_find_extent: find the 1st delayed extent covering @es->lblk
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* if it exists, otherwise, the next extent after @es->lblk.
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*
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* @inode: the inode which owns delayed extents
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* @es: delayed extent that we found
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*
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* Returns the first block of the next extent after es, otherwise
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* EXT_MAX_BLOCKS if no extent is found.
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* Delayed extent is returned via @es.
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*/
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ext4_lblk_t ext4_es_find_extent(struct inode *inode, struct extent_status *es)
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{
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struct ext4_es_tree *tree = NULL;
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struct extent_status *es1 = NULL;
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struct rb_node *node;
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ext4_lblk_t ret = EXT_MAX_BLOCKS;
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trace_ext4_es_find_extent_enter(inode, es->es_lblk);
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read_lock(&EXT4_I(inode)->i_es_lock);
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tree = &EXT4_I(inode)->i_es_tree;
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/* find extent in cache firstly */
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es->es_len = es->es_pblk = 0;
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if (tree->cache_es) {
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es1 = tree->cache_es;
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if (in_range(es->es_lblk, es1->es_lblk, es1->es_len)) {
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es_debug("%u cached by [%u/%u) %llu %llx\n",
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es->es_lblk, es1->es_lblk, es1->es_len,
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ext4_es_pblock(es1), ext4_es_status(es1));
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goto out;
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}
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}
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es1 = __es_tree_search(&tree->root, es->es_lblk);
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out:
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if (es1) {
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tree->cache_es = es1;
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es->es_lblk = es1->es_lblk;
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es->es_len = es1->es_len;
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es->es_pblk = es1->es_pblk;
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node = rb_next(&es1->rb_node);
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if (node) {
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es1 = rb_entry(node, struct extent_status, rb_node);
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ret = es1->es_lblk;
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}
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}
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read_unlock(&EXT4_I(inode)->i_es_lock);
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trace_ext4_es_find_extent_exit(inode, es, ret);
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return ret;
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}
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static struct extent_status *
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ext4_es_alloc_extent(ext4_lblk_t lblk, ext4_lblk_t len, ext4_fsblk_t pblk)
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{
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struct extent_status *es;
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es = kmem_cache_alloc(ext4_es_cachep, GFP_ATOMIC);
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if (es == NULL)
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return NULL;
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es->es_lblk = lblk;
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es->es_len = len;
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es->es_pblk = pblk;
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return es;
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}
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static void ext4_es_free_extent(struct extent_status *es)
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{
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kmem_cache_free(ext4_es_cachep, es);
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}
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/*
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* Check whether or not two extents can be merged
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* Condition:
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* - logical block number is contiguous
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* - physical block number is contiguous
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* - status is equal
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*/
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static int ext4_es_can_be_merged(struct extent_status *es1,
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struct extent_status *es2)
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{
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if (es1->es_lblk + es1->es_len != es2->es_lblk)
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return 0;
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if (ext4_es_status(es1) != ext4_es_status(es2))
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return 0;
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if ((ext4_es_is_written(es1) || ext4_es_is_unwritten(es1)) &&
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(ext4_es_pblock(es1) + es1->es_len != ext4_es_pblock(es2)))
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return 0;
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return 1;
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}
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static struct extent_status *
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ext4_es_try_to_merge_left(struct ext4_es_tree *tree, struct extent_status *es)
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{
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struct extent_status *es1;
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struct rb_node *node;
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node = rb_prev(&es->rb_node);
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if (!node)
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return es;
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es1 = rb_entry(node, struct extent_status, rb_node);
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if (ext4_es_can_be_merged(es1, es)) {
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es1->es_len += es->es_len;
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rb_erase(&es->rb_node, &tree->root);
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ext4_es_free_extent(es);
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es = es1;
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}
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return es;
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}
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static struct extent_status *
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ext4_es_try_to_merge_right(struct ext4_es_tree *tree, struct extent_status *es)
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{
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struct extent_status *es1;
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struct rb_node *node;
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node = rb_next(&es->rb_node);
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if (!node)
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return es;
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es1 = rb_entry(node, struct extent_status, rb_node);
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if (ext4_es_can_be_merged(es, es1)) {
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es->es_len += es1->es_len;
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rb_erase(node, &tree->root);
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ext4_es_free_extent(es1);
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}
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return es;
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}
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static int __es_insert_extent(struct ext4_es_tree *tree,
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struct extent_status *newes)
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{
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struct rb_node **p = &tree->root.rb_node;
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struct rb_node *parent = NULL;
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struct extent_status *es;
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while (*p) {
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parent = *p;
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es = rb_entry(parent, struct extent_status, rb_node);
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if (newes->es_lblk < es->es_lblk) {
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if (ext4_es_can_be_merged(newes, es)) {
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/*
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* Here we can modify es_lblk directly
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* because it isn't overlapped.
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*/
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es->es_lblk = newes->es_lblk;
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es->es_len += newes->es_len;
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if (ext4_es_is_written(es) ||
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ext4_es_is_unwritten(es))
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ext4_es_store_pblock(es,
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newes->es_pblk);
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es = ext4_es_try_to_merge_left(tree, es);
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goto out;
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}
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p = &(*p)->rb_left;
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} else if (newes->es_lblk > ext4_es_end(es)) {
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if (ext4_es_can_be_merged(es, newes)) {
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es->es_len += newes->es_len;
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es = ext4_es_try_to_merge_right(tree, es);
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goto out;
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}
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p = &(*p)->rb_right;
|
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} else {
|
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BUG_ON(1);
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return -EINVAL;
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}
|
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}
|
|
|
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es = ext4_es_alloc_extent(newes->es_lblk, newes->es_len,
|
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newes->es_pblk);
|
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if (!es)
|
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return -ENOMEM;
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rb_link_node(&es->rb_node, parent, p);
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rb_insert_color(&es->rb_node, &tree->root);
|
|
|
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out:
|
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tree->cache_es = es;
|
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return 0;
|
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}
|
|
|
|
/*
|
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* ext4_es_insert_extent() adds a space to a extent status tree.
|
|
*
|
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* ext4_es_insert_extent is called by ext4_da_write_begin and
|
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* ext4_es_remove_extent.
|
|
*
|
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* Return 0 on success, error code on failure.
|
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*/
|
|
int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
|
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ext4_lblk_t len, ext4_fsblk_t pblk,
|
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unsigned long long status)
|
|
{
|
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struct ext4_es_tree *tree;
|
|
struct extent_status newes;
|
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ext4_lblk_t end = lblk + len - 1;
|
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int err = 0;
|
|
|
|
es_debug("add [%u/%u) %llu %llx to extent status tree of inode %lu\n",
|
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lblk, len, pblk, status, inode->i_ino);
|
|
|
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BUG_ON(end < lblk);
|
|
|
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newes.es_lblk = lblk;
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newes.es_len = len;
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ext4_es_store_pblock(&newes, pblk);
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ext4_es_store_status(&newes, status);
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trace_ext4_es_insert_extent(inode, &newes);
|
|
|
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write_lock(&EXT4_I(inode)->i_es_lock);
|
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tree = &EXT4_I(inode)->i_es_tree;
|
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err = __es_remove_extent(tree, lblk, end);
|
|
if (err != 0)
|
|
goto error;
|
|
err = __es_insert_extent(tree, &newes);
|
|
|
|
error:
|
|
write_unlock(&EXT4_I(inode)->i_es_lock);
|
|
|
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ext4_es_print_tree(inode);
|
|
|
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return err;
|
|
}
|
|
|
|
static int __es_remove_extent(struct ext4_es_tree *tree, ext4_lblk_t lblk,
|
|
ext4_lblk_t end)
|
|
{
|
|
struct rb_node *node;
|
|
struct extent_status *es;
|
|
struct extent_status orig_es;
|
|
ext4_lblk_t len1, len2;
|
|
ext4_fsblk_t block;
|
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int err = 0;
|
|
|
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es = __es_tree_search(&tree->root, lblk);
|
|
if (!es)
|
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goto out;
|
|
if (es->es_lblk > end)
|
|
goto out;
|
|
|
|
/* Simply invalidate cache_es. */
|
|
tree->cache_es = NULL;
|
|
|
|
orig_es.es_lblk = es->es_lblk;
|
|
orig_es.es_len = es->es_len;
|
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orig_es.es_pblk = es->es_pblk;
|
|
|
|
len1 = lblk > es->es_lblk ? lblk - es->es_lblk : 0;
|
|
len2 = ext4_es_end(es) > end ? ext4_es_end(es) - end : 0;
|
|
if (len1 > 0)
|
|
es->es_len = len1;
|
|
if (len2 > 0) {
|
|
if (len1 > 0) {
|
|
struct extent_status newes;
|
|
|
|
newes.es_lblk = end + 1;
|
|
newes.es_len = len2;
|
|
if (ext4_es_is_written(&orig_es) ||
|
|
ext4_es_is_unwritten(&orig_es)) {
|
|
block = ext4_es_pblock(&orig_es) +
|
|
orig_es.es_len - len2;
|
|
ext4_es_store_pblock(&newes, block);
|
|
}
|
|
ext4_es_store_status(&newes, ext4_es_status(&orig_es));
|
|
err = __es_insert_extent(tree, &newes);
|
|
if (err) {
|
|
es->es_lblk = orig_es.es_lblk;
|
|
es->es_len = orig_es.es_len;
|
|
goto out;
|
|
}
|
|
} else {
|
|
es->es_lblk = end + 1;
|
|
es->es_len = len2;
|
|
if (ext4_es_is_written(es) ||
|
|
ext4_es_is_unwritten(es)) {
|
|
block = orig_es.es_pblk + orig_es.es_len - len2;
|
|
ext4_es_store_pblock(es, block);
|
|
}
|
|
}
|
|
goto out;
|
|
}
|
|
|
|
if (len1 > 0) {
|
|
node = rb_next(&es->rb_node);
|
|
if (node)
|
|
es = rb_entry(node, struct extent_status, rb_node);
|
|
else
|
|
es = NULL;
|
|
}
|
|
|
|
while (es && ext4_es_end(es) <= end) {
|
|
node = rb_next(&es->rb_node);
|
|
rb_erase(&es->rb_node, &tree->root);
|
|
ext4_es_free_extent(es);
|
|
if (!node) {
|
|
es = NULL;
|
|
break;
|
|
}
|
|
es = rb_entry(node, struct extent_status, rb_node);
|
|
}
|
|
|
|
if (es && es->es_lblk < end + 1) {
|
|
ext4_lblk_t orig_len = es->es_len;
|
|
|
|
len1 = ext4_es_end(es) - end;
|
|
es->es_lblk = end + 1;
|
|
es->es_len = len1;
|
|
if (ext4_es_is_written(es) || ext4_es_is_unwritten(es)) {
|
|
block = es->es_pblk + orig_len - len1;
|
|
ext4_es_store_pblock(es, block);
|
|
}
|
|
}
|
|
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* ext4_es_remove_extent() removes a space from a extent status tree.
|
|
*
|
|
* Return 0 on success, error code on failure.
|
|
*/
|
|
int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
|
|
ext4_lblk_t len)
|
|
{
|
|
struct ext4_es_tree *tree;
|
|
ext4_lblk_t end;
|
|
int err = 0;
|
|
|
|
trace_ext4_es_remove_extent(inode, lblk, len);
|
|
es_debug("remove [%u/%u) from extent status tree of inode %lu\n",
|
|
lblk, len, inode->i_ino);
|
|
|
|
end = lblk + len - 1;
|
|
BUG_ON(end < lblk);
|
|
|
|
tree = &EXT4_I(inode)->i_es_tree;
|
|
|
|
write_lock(&EXT4_I(inode)->i_es_lock);
|
|
err = __es_remove_extent(tree, lblk, end);
|
|
write_unlock(&EXT4_I(inode)->i_es_lock);
|
|
ext4_es_print_tree(inode);
|
|
return err;
|
|
}
|