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Date: Thu, 11 Jul 2013 20:52:23 +0800
From: Zheng Liu <gnehzuil.liu@...il.com>
To: Theodore Ts'o <tytso@....edu>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>,
Zheng Liu <wenqing.lz@...bao.com>
Subject: Re: [RFC PATCH 3/3] ext4: cache all of an extent tree's leaf block
upon reading
On Thu, Jul 11, 2013 at 12:39:02AM -0400, Theodore Ts'o wrote:
> When we read in an extent tree leaf block from disk, arrange to have
> all of its entries cached. In nearly all cases the in-memory
> representation will be more compact than the on-disk representation in
> the buffer cache, and it allows us to get the information without
> having to traverse the extent tree for successive extents.
>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> Cc: Zheng Liu <wenqing.lz@...bao.com>
One minor nit below. Otherwise the patch looks good to me.
Reviewed-by: Zheng Liu <wenqing.lz@...bao.com>
> ---
> fs/ext4/ext4.h | 14 +++++++-
> fs/ext4/extents.c | 84 +++++++++++++++++++++++++++++++--------------
> fs/ext4/extents_status.c | 39 ++++++++++++++++++++-
> fs/ext4/extents_status.h | 3 ++
> fs/ext4/migrate.c | 2 +-
> fs/ext4/move_extent.c | 2 +-
> include/trace/events/ext4.h | 14 +++++++-
> 7 files changed, 127 insertions(+), 31 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 6ed348d..a8497b0 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -561,6 +561,17 @@ enum {
> #define EXT4_GET_BLOCKS_NO_PUT_HOLE 0x0200
>
> /*
> + * The bit position of this flag must not overlap with any of the
> + * EXT4_GET_BLOCKS_*. It is used by ext4_ext_find_extent(),
> + * read_extent_tree_block(), ext4_split_extent_at(),
> + * ext4_ext_insert_extent(), and ext4_ext_create_new_leaf() to
> + * indicate that the we shouldn't be caching the extents when reading
> + * from the extent tree while a truncate or punch hole operation
> + * is in progress.
> + */
> +#define EXT4_EX_NOCACHE 0x0400
> +
> +/*
> * Flags used by ext4_free_blocks
> */
> #define EXT4_FREE_BLOCKS_METADATA 0x0001
> @@ -2683,7 +2694,8 @@ extern int ext4_ext_insert_extent(handle_t *, struct inode *,
> struct ext4_ext_path *,
> struct ext4_extent *, int);
> extern struct ext4_ext_path *ext4_ext_find_extent(struct inode *, ext4_lblk_t,
> - struct ext4_ext_path *);
> + struct ext4_ext_path *,
> + int flags);
> extern void ext4_ext_drop_refs(struct ext4_ext_path *);
> extern int ext4_ext_check_inode(struct inode *inode);
> extern int ext4_find_delalloc_range(struct inode *inode,
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index e174814..506c3fe 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -466,7 +466,8 @@ int ext4_ext_check_inode(struct inode *inode)
>
> static struct buffer_head *
> __read_extent_tree_block(const char *function, unsigned int line,
> - struct inode *inode, ext4_fsblk_t pblk, int depth)
> + struct inode *inode, ext4_fsblk_t pblk, int depth,
> + int flags)
> {
> struct buffer_head *bh;
> int err;
> @@ -490,6 +491,31 @@ __read_extent_tree_block(const char *function, unsigned int line,
> if (err)
> goto errout;
> set_buffer_verified(bh);
> + /*
> + * If this is a leaf block, cache all of its entries
> + */
> + if (!(flags & EXT4_EX_NOCACHE) && depth == 0) {
> + struct ext4_extent_header *eh = ext_block_hdr(bh);
> + struct ext4_extent *ex = EXT_FIRST_EXTENT(eh);
> + int i;
> +
> + for (i = eh->eh_entries; i > 0; i--, ex++) {
Here I get a warning message when I use the following command to build
the ext4 kernel module.
$ make M=fs/ext4 C=2 CF=-D__CHECK_ENDIAN__
CHECK fs/ext4/extents.c
fs/ext4/extents.c:502:24: warning: incorrect type in assignment (different base types)
fs/ext4/extents.c:502:24: expected int [signed] i
fs/ext4/extents.c:502:24: got restricted __le16 [usertype] eh_entries
- Zheng
> + unsigned int status = EXTENT_STATUS_WRITTEN;
> + ext4_lblk_t prev = 0, lblk = le32_to_cpu(ex->ee_block);
> + int len = ext4_ext_get_actual_len(ex);
> +
> + if (prev && (prev != lblk))
> + ext4_es_cache_extent(inode, prev,
> + lblk - prev, ~0,
> + EXTENT_STATUS_HOLE);
> +
> + if (ext4_ext_is_uninitialized(ex))
> + status = EXTENT_STATUS_UNWRITTEN;
> + ext4_es_cache_extent(inode, lblk, len,
> + ext4_ext_pblock(ex), status);
> + prev = lblk + len;
> + }
> + }
> return bh;
> errout:
> put_bh(bh);
> @@ -497,8 +523,9 @@ errout:
>
> }
>
> -#define read_extent_tree_block(inode, pblk, depth) \
> - __read_extent_tree_block(__func__, __LINE__, (inode), (pblk), (depth))
> +#define read_extent_tree_block(inode, pblk, depth, flags) \
> + __read_extent_tree_block(__func__, __LINE__, (inode), (pblk), \
> + (depth), (flags))
>
> #ifdef EXT_DEBUG
> static void ext4_ext_show_path(struct inode *inode, struct ext4_ext_path *path)
> @@ -732,7 +759,7 @@ int ext4_ext_tree_init(handle_t *handle, struct inode *inode)
>
> struct ext4_ext_path *
> ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
> - struct ext4_ext_path *path)
> + struct ext4_ext_path *path, int flags)
> {
> struct ext4_extent_header *eh;
> struct buffer_head *bh;
> @@ -764,7 +791,8 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
> path[ppos].p_depth = i;
> path[ppos].p_ext = NULL;
>
> - bh = read_extent_tree_block(inode, path[ppos].p_block, --i);
> + bh = read_extent_tree_block(inode, path[ppos].p_block, --i,
> + flags);
> if (IS_ERR(bh)) {
> ret = PTR_ERR(bh);
> goto err;
> @@ -1201,7 +1229,8 @@ out:
> * if no free index is found, then it requests in-depth growing.
> */
> static int ext4_ext_create_new_leaf(handle_t *handle, struct inode *inode,
> - unsigned int flags,
> + unsigned int mb_flags,
> + unsigned int gb_flags,
> struct ext4_ext_path *path,
> struct ext4_extent *newext)
> {
> @@ -1223,7 +1252,7 @@ repeat:
> if (EXT_HAS_FREE_INDEX(curp)) {
> /* if we found index with free entry, then use that
> * entry: create all needed subtree and add new leaf */
> - err = ext4_ext_split(handle, inode, flags, path, newext, i);
> + err = ext4_ext_split(handle, inode, mb_flags, path, newext, i);
> if (err)
> goto out;
>
> @@ -1231,12 +1260,12 @@ repeat:
> ext4_ext_drop_refs(path);
> path = ext4_ext_find_extent(inode,
> (ext4_lblk_t)le32_to_cpu(newext->ee_block),
> - path);
> + path, gb_flags);
> if (IS_ERR(path))
> err = PTR_ERR(path);
> } else {
> /* tree is full, time to grow in depth */
> - err = ext4_ext_grow_indepth(handle, inode, flags, newext);
> + err = ext4_ext_grow_indepth(handle, inode, mb_flags, newext);
> if (err)
> goto out;
>
> @@ -1244,7 +1273,7 @@ repeat:
> ext4_ext_drop_refs(path);
> path = ext4_ext_find_extent(inode,
> (ext4_lblk_t)le32_to_cpu(newext->ee_block),
> - path);
> + path, gb_flags);
> if (IS_ERR(path)) {
> err = PTR_ERR(path);
> goto out;
> @@ -1417,7 +1446,7 @@ got_index:
> while (++depth < path->p_depth) {
> /* subtract from p_depth to get proper eh_depth */
> bh = read_extent_tree_block(inode, *logical,
> - path->p_depth - depth);
> + path->p_depth - depth, 0);
> if (IS_ERR(bh))
> return PTR_ERR(bh);
> eh = ext_block_hdr(bh);
> @@ -1426,7 +1455,7 @@ got_index:
> put_bh(bh);
> }
>
> - bh = read_extent_tree_block(inode, *logical, path->p_depth - depth);
> + bh = read_extent_tree_block(inode, *logical, path->p_depth - depth, 0);
> if (IS_ERR(bh))
> return PTR_ERR(bh);
> eh = ext_block_hdr(bh);
> @@ -1788,7 +1817,7 @@ out:
> */
> int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
> struct ext4_ext_path *path,
> - struct ext4_extent *newext, int flag)
> + struct ext4_extent *newext, int gb_flags)
> {
> struct ext4_extent_header *eh;
> struct ext4_extent *ex, *fex;
> @@ -1797,7 +1826,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
> int depth, len, err;
> ext4_lblk_t next;
> unsigned uninitialized = 0;
> - int flags = 0;
> + int mb_flags = 0;
>
> if (unlikely(ext4_ext_get_actual_len(newext) == 0)) {
> EXT4_ERROR_INODE(inode, "ext4_ext_get_actual_len(newext) == 0");
> @@ -1812,7 +1841,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
> }
>
> /* try to insert block into found extent and return */
> - if (ex && !(flag & EXT4_GET_BLOCKS_PRE_IO)) {
> + if (ex && !(gb_flags & EXT4_GET_BLOCKS_PRE_IO)) {
>
> /*
> * Try to see whether we should rather test the extent on
> @@ -1915,7 +1944,7 @@ prepend:
> if (next != EXT_MAX_BLOCKS) {
> ext_debug("next leaf block - %u\n", next);
> BUG_ON(npath != NULL);
> - npath = ext4_ext_find_extent(inode, next, NULL);
> + npath = ext4_ext_find_extent(inode, next, NULL, 0);
> if (IS_ERR(npath))
> return PTR_ERR(npath);
> BUG_ON(npath->p_depth != path->p_depth);
> @@ -1934,9 +1963,10 @@ prepend:
> * There is no free space in the found leaf.
> * We're gonna add a new leaf in the tree.
> */
> - if (flag & EXT4_GET_BLOCKS_METADATA_NOFAIL)
> - flags = EXT4_MB_USE_RESERVED;
> - err = ext4_ext_create_new_leaf(handle, inode, flags, path, newext);
> + if (gb_flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
> + mb_flags = EXT4_MB_USE_RESERVED;
> + err = ext4_ext_create_new_leaf(handle, inode, mb_flags, gb_flags,
> + path, newext);
> if (err)
> goto cleanup;
> depth = ext_depth(inode);
> @@ -2002,7 +2032,7 @@ has_space:
>
> merge:
> /* try to merge extents */
> - if (!(flag & EXT4_GET_BLOCKS_PRE_IO))
> + if (!(gb_flags & EXT4_GET_BLOCKS_PRE_IO))
> ext4_ext_try_to_merge(handle, inode, path, nearex);
>
>
> @@ -2045,7 +2075,7 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
> path = NULL;
> }
>
> - path = ext4_ext_find_extent(inode, block, path);
> + path = ext4_ext_find_extent(inode, block, path, 0);
> if (IS_ERR(path)) {
> up_read(&EXT4_I(inode)->i_data_sem);
> err = PTR_ERR(path);
> @@ -2707,7 +2737,7 @@ again:
> ext4_lblk_t ee_block;
>
> /* find extent for this block */
> - path = ext4_ext_find_extent(inode, end, NULL);
> + path = ext4_ext_find_extent(inode, end, NULL, EXT4_EX_NOCACHE);
> if (IS_ERR(path)) {
> ext4_journal_stop(handle);
> return PTR_ERR(path);
> @@ -2749,6 +2779,7 @@ again:
> */
> err = ext4_split_extent_at(handle, inode, path,
> end + 1, split_flag,
> + EXT4_EX_NOCACHE |
> EXT4_GET_BLOCKS_PRE_IO |
> EXT4_GET_BLOCKS_METADATA_NOFAIL);
>
> @@ -2825,7 +2856,8 @@ again:
> i + 1, ext4_idx_pblock(path[i].p_idx));
> memset(path + i + 1, 0, sizeof(*path));
> bh = read_extent_tree_block(inode,
> - ext4_idx_pblock(path[i].p_idx), depth - i - 1);
> + ext4_idx_pblock(path[i].p_idx), depth - i - 1,
> + EXT4_EX_NOCACHE);
> if (IS_ERR(bh)) {
> err = PTR_ERR(bh);
> break;
> @@ -3168,7 +3200,7 @@ static int ext4_split_extent(handle_t *handle,
> * result in split of original leaf or extent zeroout.
> */
> ext4_ext_drop_refs(path);
> - path = ext4_ext_find_extent(inode, map->m_lblk, path);
> + path = ext4_ext_find_extent(inode, map->m_lblk, path, 0);
> if (IS_ERR(path))
> return PTR_ERR(path);
> depth = ext_depth(inode);
> @@ -3552,7 +3584,7 @@ static int ext4_convert_unwritten_extents_endio(handle_t *handle,
> if (err < 0)
> goto out;
> ext4_ext_drop_refs(path);
> - path = ext4_ext_find_extent(inode, map->m_lblk, path);
> + path = ext4_ext_find_extent(inode, map->m_lblk, path, 0);
> if (IS_ERR(path)) {
> err = PTR_ERR(path);
> goto out;
> @@ -4039,7 +4071,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
> trace_ext4_ext_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
>
> /* find extent for this block */
> - path = ext4_ext_find_extent(inode, map->m_lblk, NULL);
> + path = ext4_ext_find_extent(inode, map->m_lblk, NULL, 0);
> if (IS_ERR(path)) {
> err = PTR_ERR(path);
> path = NULL;
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 7358fb3..a84804c 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -417,7 +417,7 @@ static void ext4_es_insert_extent_ext_check(struct inode *inode,
> unsigned short ee_len;
> int depth, ee_status, es_status;
>
> - path = ext4_ext_find_extent(inode, es->es_lblk, NULL);
> + path = ext4_ext_find_extent(inode, es->es_lblk, NULL, EXT4_EX_NOCACHE);
> if (IS_ERR(path))
> return;
>
> @@ -678,6 +678,43 @@ error:
> }
>
> /*
> + * ext4_es_cache_extent() inserts information into the extent status
> + * tree if and only if there isn't information about the range in
> + * question already.
> + */
> +void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
> + ext4_lblk_t len, ext4_fsblk_t pblk,
> + unsigned int status)
> +{
> + struct extent_status *es;
> + struct extent_status newes;
> + ext4_lblk_t end = lblk + len - 1;
> +
> + es_debug("cache [%u/%u) %llu %x to extent status tree of inode %lu\n",
> + lblk, len, pblk, status, inode->i_ino);
> + if (!len)
> + return;
> +
> + BUG_ON(end < lblk);
> +
> + write_lock(&EXT4_I(inode)->i_es_lock);
> +
> + es = __es_tree_search(&EXT4_I(inode)->i_es_tree.root, lblk);
> + if (es && ((es->es_lblk <= lblk) || (es->es_lblk <= end)))
> + goto out;
> +
> + newes.es_lblk = lblk;
> + newes.es_len = len;
> + ext4_es_store_pblock(&newes, pblk);
> + ext4_es_store_status(&newes, status);
> + trace_ext4_es_cache_extent(inode, &newes);
> +
> + __es_insert_extent(inode, &newes);
> +out:
> + write_unlock(&EXT4_I(inode)->i_es_lock);
> +}
> +
> +/*
> * ext4_es_lookup_extent() looks up an extent in extent status tree.
> *
> * ext4_es_lookup_extent is called by ext4_map_blocks/ext4_da_map_blocks.
> diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
> index ae1be58..23348d1 100644
> --- a/fs/ext4/extents_status.h
> +++ b/fs/ext4/extents_status.h
> @@ -71,6 +71,9 @@ extern void ext4_es_init_tree(struct ext4_es_tree *tree);
> extern int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
> ext4_lblk_t len, ext4_fsblk_t pblk,
> unsigned int status);
> +extern void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
> + ext4_lblk_t len, ext4_fsblk_t pblk,
> + unsigned int status);
> extern int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
> ext4_lblk_t len);
> extern void ext4_es_find_delayed_extent_range(struct inode *inode,
> diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
> index 49e8bdf..f99bdb8 100644
> --- a/fs/ext4/migrate.c
> +++ b/fs/ext4/migrate.c
> @@ -39,7 +39,7 @@ static int finish_range(handle_t *handle, struct inode *inode,
> newext.ee_block = cpu_to_le32(lb->first_block);
> newext.ee_len = cpu_to_le16(lb->last_block - lb->first_block + 1);
> ext4_ext_store_pblock(&newext, lb->first_pblock);
> - path = ext4_ext_find_extent(inode, lb->first_block, NULL);
> + path = ext4_ext_find_extent(inode, lb->first_block, NULL, 0);
>
> if (IS_ERR(path)) {
> retval = PTR_ERR(path);
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index e86dddb..7fa4d85 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -37,7 +37,7 @@ get_ext_path(struct inode *inode, ext4_lblk_t lblock,
> int ret = 0;
> struct ext4_ext_path *path;
>
> - path = ext4_ext_find_extent(inode, lblock, *orig_path);
> + path = ext4_ext_find_extent(inode, lblock, *orig_path, EXT4_EX_NOCACHE);
> if (IS_ERR(path))
> ret = PTR_ERR(path);
> else if (path[ext_depth(inode)].p_ext == NULL)
> diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
> index 47a355b..d892b55 100644
> --- a/include/trace/events/ext4.h
> +++ b/include/trace/events/ext4.h
> @@ -2192,7 +2192,7 @@ TRACE_EVENT(ext4_ext_remove_space_done,
> (unsigned short) __entry->eh_entries)
> );
>
> -TRACE_EVENT(ext4_es_insert_extent,
> +DECLARE_EVENT_CLASS(ext4__es_extent,
> TP_PROTO(struct inode *inode, struct extent_status *es),
>
> TP_ARGS(inode, es),
> @@ -2222,6 +2222,18 @@ TRACE_EVENT(ext4_es_insert_extent,
> __entry->pblk, show_extent_status(__entry->status))
> );
>
> +DEFINE_EVENT(ext4__es_extent, ext4_es_insert_extent,
> + TP_PROTO(struct inode *inode, struct extent_status *es),
> +
> + TP_ARGS(inode, es)
> +);
> +
> +DEFINE_EVENT(ext4__es_extent, ext4_es_cache_extent,
> + TP_PROTO(struct inode *inode, struct extent_status *es),
> +
> + TP_ARGS(inode, es)
> +);
> +
> TRACE_EVENT(ext4_es_remove_extent,
> TP_PROTO(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len),
>
> --
> 1.7.12.rc0.22.gcdd159b
>
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