ext4: add operations on extent status tree (654598be) · Commits · e / devices / android_kernel_oneplus_sm7250

fs/ext4/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -7,7 +7,7 @@ obj-$(CONFIG_EXT4_FS) += ext4.o
		ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
		ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
		ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o \
		mmp.o indirect.o
		mmp.o indirect.o extents_status.o

		ext4-$(CONFIG_EXT4_FS_XATTR) += xattr.o xattr_user.o xattr_trusted.o
		ext4-$(CONFIG_EXT4_FS_POSIX_ACL) += acl.o

fs/ext4/extents_status.c

0 → 100644

+492 −0

Original line number	Diff line number	Diff line
		/*
		* fs/ext4/extents_status.c
		*
		* Written by Yongqiang Yang <xiaoqiangnk@gmail.com>
		* Modified by
		* Allison Henderson <achender@linux.vnet.ibm.com>
		* Hugh Dickins <hughd@google.com>
		* Zheng Liu <wenqing.lz@taobao.com>
		*
		* Ext4 extents status tree core functions.
		*/
		#include <linux/rbtree.h>
		#include "ext4.h"
		#include "extents_status.h"
		#include "ext4_extents.h"

		/*
		* According to previous discussion in Ext4 Developer Workshop, we
		* will introduce a new structure called io tree to track all extent
		* status in order to solve some problems that we have met
		* (e.g. Reservation space warning), and provide extent-level locking.
		* Delay extent tree is the first step to achieve this goal. It is
		* original built by Yongqiang Yang. At that time it is called delay
		* extent tree, whose goal is only track delay extent in memory to
		* simplify the implementation of fiemap and bigalloc, and introduce
		* lseek SEEK_DATA/SEEK_HOLE support. That is why it is still called
		* delay extent tree at the following comment. But for better
		* understand what it does, it has been rename to extent status tree.
		*
		* Currently the first step has been done. All delay extents are
		* tracked in the tree. It maintains the delay extent when a delay
		* allocation is issued, and the delay extent is written out or
		* invalidated. Therefore the implementation of fiemap and bigalloc
		* are simplified, and SEEK_DATA/SEEK_HOLE are introduced.
		*
		* The following comment describes the implemenmtation of extent
		* status tree and future works.
		*/

		/*
		* extents status tree implementation for ext4.
		*
		*
		* ==========================================================================
		* Extents status encompass delayed extents and extent locks
		*
		* 1. Why delayed extent implementation ?
		*
		* Without delayed extent, ext4 identifies a delayed extent by looking
		* up page cache, this has several deficiencies - complicated, buggy,
		* and inefficient code.
		*
		* FIEMAP, SEEK_HOLE/DATA, bigalloc, punch hole and writeout all need
		* to know if a block or a range of blocks are belonged to a delayed
		* extent.
		*
		* Let us have a look at how they do without delayed extents implementation.
		* -- FIEMAP
		* FIEMAP looks up page cache to identify delayed allocations from holes.
		*
		* -- SEEK_HOLE/DATA
		* SEEK_HOLE/DATA has the same problem as FIEMAP.
		*
		* -- bigalloc
		* bigalloc looks up page cache to figure out if a block is
		* already under delayed allocation or not to determine whether
		* quota reserving is needed for the cluster.
		*
		* -- punch hole
		* punch hole looks up page cache to identify a delayed extent.
		*
		* -- writeout
		* Writeout looks up whole page cache to see if a buffer is
		* mapped, If there are not very many delayed buffers, then it is
		* time comsuming.
		*
		* With delayed extents implementation, FIEMAP, SEEK_HOLE/DATA,
		* bigalloc and writeout can figure out if a block or a range of
		* blocks is under delayed allocation(belonged to a delayed extent) or
		* not by searching the delayed extent tree.
		*
		*
		* ==========================================================================
		* 2. ext4 delayed extents impelmentation
		*
		* -- delayed extent
		* A delayed extent is a range of blocks which are contiguous
		* logically and under delayed allocation. Unlike extent in
		* ext4, delayed extent in ext4 is a in-memory struct, there is
		* no corresponding on-disk data. There is no limit on length of
		* delayed extent, so a delayed extent can contain as many blocks
		* as they are contiguous logically.
		*
		* -- delayed extent tree
		* Every inode has a delayed extent tree and all under delayed
		* allocation blocks are added to the tree as delayed extents.
		* Delayed extents in the tree are ordered by logical block no.
		*
		* -- operations on a delayed extent tree
		* There are three operations on a delayed extent tree: find next
		* delayed extent, adding a space(a range of blocks) and removing
		* a space.
		*
		* -- race on a delayed extent tree
		* Delayed extent tree is protected inode->i_es_lock.
		*
		*
		* ==========================================================================
		* 3. performance analysis
		* -- overhead
		* 1. There is a cache extent for write access, so if writes are
		* not very random, adding space operaions are in O(1) time.
		*
		* -- gain
		* 2. Code is much simpler, more readable, more maintainable and
		* more efficient.
		*
		*
		* ==========================================================================
		* 4. TODO list
		* -- Track all extent status
		*
		* -- Improve get block process
		*
		* -- Extent-level locking
		*/

		static struct kmem_cache *ext4_es_cachep;

		int __init ext4_init_es(void)
		{
		ext4_es_cachep = KMEM_CACHE(extent_status, SLAB_RECLAIM_ACCOUNT);
		if (ext4_es_cachep == NULL)
		return -ENOMEM;
		return 0;
		}

		void ext4_exit_es(void)
		{
		if (ext4_es_cachep)
		kmem_cache_destroy(ext4_es_cachep);
		}

		void ext4_es_init_tree(struct ext4_es_tree *tree)
		{
		tree->root = RB_ROOT;
		tree->cache_es = NULL;
		}

		#ifdef ES_DEBUG__
		static void ext4_es_print_tree(struct inode *inode)
		{
		struct ext4_es_tree *tree;
		struct rb_node *node;

		printk(KERN_DEBUG "status extents for inode %lu:", inode->i_ino);
		tree = &EXT4_I(inode)->i_es_tree;
		node = rb_first(&tree->root);
		while (node) {
		struct extent_status *es;
		es = rb_entry(node, struct extent_status, rb_node);
		printk(KERN_DEBUG " [%u/%u)", es->start, es->len);
		node = rb_next(node);
		}
		printk(KERN_DEBUG "\n");
		}
		#else
		#define ext4_es_print_tree(inode)
		#endif

		static inline ext4_lblk_t extent_status_end(struct extent_status *es)
		{
		BUG_ON(es->start + es->len < es->start);
		return es->start + es->len - 1;
		}

		/*
		* search through the tree for an delayed extent with a given offset. If
		* it can't be found, try to find next extent.
		*/
		static struct extent_status __es_tree_search(struct rb_root root,
		ext4_lblk_t offset)
		{
		struct rb_node *node = root->rb_node;
		struct extent_status *es = NULL;

		while (node) {
		es = rb_entry(node, struct extent_status, rb_node);
		if (offset < es->start)
		node = node->rb_left;
		else if (offset > extent_status_end(es))
		node = node->rb_right;
		else
		return es;
		}

		if (es && offset < es->start)
		return es;

		if (es && offset > extent_status_end(es)) {
		node = rb_next(&es->rb_node);
		return node ? rb_entry(node, struct extent_status, rb_node) :
		NULL;
		}

		return NULL;
		}

		/*
		* ext4_es_find_extent: find the 1st delayed extent covering @es->start
		* if it exists, otherwise, the next extent after @es->start.
		*
		* @inode: the inode which owns delayed extents
		* @es: delayed extent that we found
		*
		* Returns the first block of the next extent after es, otherwise
		* EXT_MAX_BLOCKS if no delay extent is found.
		* Delayed extent is returned via @es.
		*/
		ext4_lblk_t ext4_es_find_extent(struct inode inode, struct extent_status es)
		{
		struct ext4_es_tree *tree = NULL;
		struct extent_status *es1 = NULL;
		struct rb_node *node;
		ext4_lblk_t ret = EXT_MAX_BLOCKS;

		read_lock(&EXT4_I(inode)->i_es_lock);
		tree = &EXT4_I(inode)->i_es_tree;

		/* find delay extent in cache firstly */
		if (tree->cache_es) {
		es1 = tree->cache_es;
		if (in_range(es->start, es1->start, es1->len)) {
		es_debug("%u cached by [%u/%u)\n",
		es->start, es1->start, es1->len);
		goto out;
		}
		}

		es->len = 0;
		es1 = __es_tree_search(&tree->root, es->start);

		out:
		if (es1) {
		tree->cache_es = es1;
		es->start = es1->start;
		es->len = es1->len;
		node = rb_next(&es1->rb_node);
		if (node) {
		es1 = rb_entry(node, struct extent_status, rb_node);
		ret = es1->start;
		}
		}

		read_unlock(&EXT4_I(inode)->i_es_lock);
		return ret;
		}

		static struct extent_status *
		ext4_es_alloc_extent(ext4_lblk_t start, ext4_lblk_t len)
		{
		struct extent_status *es;
		es = kmem_cache_alloc(ext4_es_cachep, GFP_ATOMIC);
		if (es == NULL)
		return NULL;
		es->start = start;
		es->len = len;
		return es;
		}

		static void ext4_es_free_extent(struct extent_status *es)
		{
		kmem_cache_free(ext4_es_cachep, es);
		}

		static struct extent_status *
		ext4_es_try_to_merge_left(struct ext4_es_tree tree, struct extent_status es)
		{
		struct extent_status *es1;
		struct rb_node *node;

		node = rb_prev(&es->rb_node);
		if (!node)
		return es;

		es1 = rb_entry(node, struct extent_status, rb_node);
		if (es->start == extent_status_end(es1) + 1) {
		es1->len += es->len;
		rb_erase(&es->rb_node, &tree->root);
		ext4_es_free_extent(es);
		es = es1;
		}

		return es;
		}

		static struct extent_status *
		ext4_es_try_to_merge_right(struct ext4_es_tree tree, struct extent_status es)
		{
		struct extent_status *es1;
		struct rb_node *node;

		node = rb_next(&es->rb_node);
		if (!node)
		return es;

		es1 = rb_entry(node, struct extent_status, rb_node);
		if (es1->start == extent_status_end(es) + 1) {
		es->len += es1->len;
		rb_erase(node, &tree->root);
		ext4_es_free_extent(es1);
		}

		return es;
		}

		static int __es_insert_extent(struct ext4_es_tree *tree, ext4_lblk_t offset,
		ext4_lblk_t len)
		{
		struct rb_node **p = &tree->root.rb_node;
		struct rb_node *parent = NULL;
		struct extent_status *es;
		ext4_lblk_t end = offset + len - 1;

		BUG_ON(end < offset);
		es = tree->cache_es;
		if (es && offset == (extent_status_end(es) + 1)) {
		es_debug("cached by [%u/%u)\n", es->start, es->len);
		es->len += len;
		es = ext4_es_try_to_merge_right(tree, es);
		goto out;
		} else if (es && es->start == end + 1) {
		es_debug("cached by [%u/%u)\n", es->start, es->len);
		es->start = offset;
		es->len += len;
		es = ext4_es_try_to_merge_left(tree, es);
		goto out;
		} else if (es && es->start <= offset &&
		end <= extent_status_end(es)) {
		es_debug("cached by [%u/%u)\n", es->start, es->len);
		goto out;
		}

		while (*p) {
		parent = *p;
		es = rb_entry(parent, struct extent_status, rb_node);

		if (offset < es->start) {
		if (es->start == end + 1) {
		es->start = offset;
		es->len += len;
		es = ext4_es_try_to_merge_left(tree, es);
		goto out;
		}
		p = &(*p)->rb_left;
		} else if (offset > extent_status_end(es)) {
		if (offset == extent_status_end(es) + 1) {
		es->len += len;
		es = ext4_es_try_to_merge_right(tree, es);
		goto out;
		}
		p = &(*p)->rb_right;
		} else {
		if (extent_status_end(es) <= end)
		es->len = offset - es->start + len;
		goto out;
		}
		}

		es = ext4_es_alloc_extent(offset, len);
		if (!es)
		return -ENOMEM;
		rb_link_node(&es->rb_node, parent, p);
		rb_insert_color(&es->rb_node, &tree->root);

		out:
		tree->cache_es = es;
		return 0;
		}

		/*
		* ext4_es_insert_extent() adds a space to a delayed extent tree.
		* Caller holds inode->i_es_lock.
		*
		* ext4_es_insert_extent is called by ext4_da_write_begin and
		* ext4_es_remove_extent.
		*
		* Return 0 on success, error code on failure.
		*/
		int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t offset,
		ext4_lblk_t len)
		{
		struct ext4_es_tree *tree;
		int err = 0;

		es_debug("add [%u/%u) to extent status tree of inode %lu\n",
		offset, len, inode->i_ino);

		write_lock(&EXT4_I(inode)->i_es_lock);
		tree = &EXT4_I(inode)->i_es_tree;
		err = __es_insert_extent(tree, offset, len);
		write_unlock(&EXT4_I(inode)->i_es_lock);

		ext4_es_print_tree(inode);

		return err;
		}

		/*
		* ext4_es_remove_extent() removes a space from a delayed extent tree.
		* Caller holds inode->i_es_lock.
		*
		* Return 0 on success, error code on failure.
		*/
		int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t offset,
		ext4_lblk_t len)
		{
		struct rb_node *node;
		struct ext4_es_tree *tree;
		struct extent_status *es;
		struct extent_status orig_es;
		ext4_lblk_t len1, len2, end;
		int err = 0;

		es_debug("remove [%u/%u) from extent status tree of inode %lu\n",
		offset, len, inode->i_ino);

		end = offset + len - 1;
		BUG_ON(end < offset);
		write_lock(&EXT4_I(inode)->i_es_lock);
		tree = &EXT4_I(inode)->i_es_tree;
		es = __es_tree_search(&tree->root, offset);
		if (!es)
		goto out;
		if (es->start > end)
		goto out;

		/* Simply invalidate cache_es. */
		tree->cache_es = NULL;

		orig_es.start = es->start;
		orig_es.len = es->len;
		len1 = offset > es->start ? offset - es->start : 0;
		len2 = extent_status_end(es) > end ?
		extent_status_end(es) - end : 0;
		if (len1 > 0)
		es->len = len1;
		if (len2 > 0) {
		if (len1 > 0) {
		err = __es_insert_extent(tree, end + 1, len2);
		if (err) {
		es->start = orig_es.start;
		es->len = orig_es.len;
		goto out;
		}
		} else {
		es->start = end + 1;
		es->len = len2;
		}
		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 && extent_status_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->start < end + 1) {
		len1 = extent_status_end(es) - end;
		es->start = end + 1;
		es->len = len1;
		}

		out:
		write_unlock(&EXT4_I(inode)->i_es_lock);
		ext4_es_print_tree(inode);
		return err;
		}

fs/ext4/extents_status.h

+20 −0

Original line number	Diff line number	Diff line
		@@ -11,6 +11,15 @@
		#ifndef _EXT4_EXTENTS_STATUS_H
		#define _EXT4_EXTENTS_STATUS_H

		/*
		* Turn on ES_DEBUG__ to get lots of info about extent status operations.
		*/
		#ifdef ES_DEBUG__
		#define es_debug(fmt, ...) printk(fmt, ##__VA_ARGS__)
		#else
		#define es_debug(fmt, ...) no_printk(fmt, ##__VA_ARGS__)
		#endif

		struct extent_status {
		struct rb_node rb_node;
		ext4_lblk_t start; /* first block extent covers */
		@@ -22,4 +31,15 @@ struct ext4_es_tree {
		struct extent_status cache_es; / recently accessed extent */
		};

		extern int __init ext4_init_es(void);
		extern void ext4_exit_es(void);
		extern void ext4_es_init_tree(struct ext4_es_tree *tree);

		extern int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t start,
		ext4_lblk_t len);
		extern int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t start,
		ext4_lblk_t len);
		extern ext4_lblk_t ext4_es_find_extent(struct inode *inode,
		struct extent_status *es);

		#endif /* _EXT4_EXTENTS_STATUS_H */