Re: [Ext2-devel] [PATCH 1/9] extents for ext4

Mingming Cao
2006-08-11T21:50:09Z

On Fri, 2006-08-11 at 13:57 -0700, Randy.Dunlap wrote:
> On Thu, 10 Aug 2006 13:29:56 +0400 Alex Tomas wrote:
>
> > AM> - The existing comments could benefit from some rework by a
> > AM> native English speaker.
> >
> > could someone assist here, please?
>
> See if this helps.
> Patch applies on top of all ext4 patches from
> http://ext2.sourceforge.net/48bitext3/patches/latest/.
>
> ---
> From: Randy Dunlap <rdunlap@xenotime.net>
>
> Clean up comments in ext4-extents patch.
>
> Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>

Thanks, Randy, I added this to the queue.

> ---
> fs/ext4/extents.c | 226 ++++++++++++++++++++++------------------
> include/linux/ext4_fs_extents.h | 54 ++++-----
> include/linux/ext4_jbd2.h | 4
> 3 files changed, 157 insertions(+), 127 deletions(-)
>
> --- linux-2618-rc4-ext4.orig/include/linux/ext4_jbd2.h
> +++ linux-2618-rc4-ext4/include/linux/ext4_jbd2.h
> @@ -28,8 +28,8 @@
> * indirection blocks, the group and superblock summaries, and the data
> * block to complete the transaction.
> *
> - * For extents-enabled fs we may have to allocate and modify upto
> - * 5 levels of tree + root which is stored in inode. */
> + * For extents-enabled fs we may have to allocate and modify up to
> + * 5 levels of tree + root which are stored in the inode. */
>
> #define EXT4_SINGLEDATA_TRANS_BLOCKS(sb) \
> (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS) \
> --- linux-2618-rc4-ext4.orig/include/linux/ext4_fs_extents.h
> +++ linux-2618-rc4-ext4/include/linux/ext4_fs_extents.h
> @@ -22,29 +22,29 @@
> #include <linux/ext4_fs.h>
>
> /*
> - * with AGRESSIVE_TEST defined capacity of index/leaf blocks
> - * become very little, so index split, in-depth growing and
> - * other hard changes happens much more often
> - * this is for debug purposes only
> + * With AGRESSIVE_TEST defined, the capacity of index/leaf blocks
> + * becomes very small, so index split, in-depth growing and
> + * other hard changes happen much more often.
> + * This is for debug purposes only.
> */
> #define AGRESSIVE_TEST_
>
> /*
> - * with EXTENTS_STATS defined number of blocks and extents
> - * are collected in truncate path. they'll be showed at
> - * umount time
> + * With EXTENTS_STATS defined, the number of blocks and extents
> + * are collected in the truncate path. They'll be shown at
> + * umount time.
> */
> #define EXTENTS_STATS__
>
> /*
> - * if CHECK_BINSEARCH defined, then results of binary search
> - * will be checked by linear search
> + * If CHECK_BINSEARCH is defined, then the results of the binary search
> + * will also be checked by linear search.
> */
> #define CHECK_BINSEARCH__
>
> /*
> - * if EXT_DEBUG is defined you can use 'extdebug' mount option
> - * to get lots of info what's going on
> + * If EXT_DEBUG is defined you can use the 'extdebug' mount option
> + * to get lots of info about what's going on.
> */
> #define EXT_DEBUG__
> #ifdef EXT_DEBUG
> @@ -54,58 +54,58 @@
> #endif
>
> /*
> - * if EXT_STATS is defined then stats numbers are collected
> - * these number will be displayed at umount time
> + * If EXT_STATS is defined then stats numbers are collected.
> + * These number will be displayed at umount time.
> */
> #define EXT_STATS_
>
>
> /*
> - * ext4_inode has i_block array (60 bytes total)
> - * first 12 bytes store ext4_extent_header
> - * the remain stores array of ext4_extent
> + * ext4_inode has i_block array (60 bytes total).
> + * The first 12 bytes store ext4_extent_header;
> + * the remainder stores an array of ext4_extent.
> */
>
> /*
> - * this is extent on-disk structure
> - * it's used at the bottom of the tree
> + * This is the extent on-disk structure.
> + * It's used at the bottom of the tree.
> */
> struct ext4_extent {
> __le32 ee_block; /* first logical block extent covers */
> __le16 ee_len; /* number of blocks covered by extent */
> __le16 ee_start_hi; /* high 16 bits of physical block */
> - __le32 ee_start; /* low 32 bigs of physical block */
> + __le32 ee_start; /* low 32 bits of physical block */
> };
>
> /*
> - * this is index on-disk structure
> - * it's used at all the levels, but the bottom
> + * This is index on-disk structure.
> + * It's used at all the levels except the bottom.
> */
> struct ext4_extent_idx {
> __le32 ei_block; /* index covers logical blocks from 'block' */
> __le32 ei_leaf; /* pointer to the physical block of the next *
> - * level. leaf or next index could bet here */
> + * level. leaf or next index could be there */
> __le16 ei_leaf_hi; /* high 16 bits of physical block */
> __u16 ei_unused;
> };
>
> /*
> - * each block (leaves and indexes), even inode-stored has header
> + * Each block (leaves and indexes), even inode-stored has header.
> */
> struct ext4_extent_header {
> __le16 eh_magic; /* probably will support different formats */
> __le16 eh_entries; /* number of valid entries */
> __le16 eh_max; /* capacity of store in entries */
> - __le16 eh_depth; /* has tree real underlaying blocks? */
> + __le16 eh_depth; /* has tree real underlying blocks? */
> __le32 eh_generation; /* generation of the tree */
> };
>
> #define EXT4_EXT_MAGIC cpu_to_le16(0xf30a)
>
> /*
> - * array of ext4_ext_path contains path to some extent
> - * creation/lookup routines use it for traversal/splitting/etc
> - * truncate uses it to simulate recursive walking
> + * Array of ext4_ext_path contains path to some extent.
> + * Creation/lookup routines use it for traversal/splitting/etc.
> + * Truncate uses it to simulate recursive walking.
> */
> struct ext4_ext_path {
> ext4_fsblk_t p_block;
> --- linux-2618-rc4-ext4.orig/fs/ext4/extents.c
> +++ linux-2618-rc4-ext4/fs/ext4/extents.c
> @@ -44,7 +44,10 @@
> #include <asm/uaccess.h>
>
>
> -/* this macro combines low and hi parts of phys. blocknr into ext4_fsblk_t */
> +/*
> + * ext_pblock:
> + * combine low and high parts of physical block number into ext4_fsblk_t
> + */
> static inline ext4_fsblk_t ext_pblock(struct ext4_extent *ex)
> {
> ext4_fsblk_t block;
> @@ -55,7 +58,10 @@ static inline ext4_fsblk_t ext_pblock(st
> return block;
> }
>
> -/* this macro combines low and hi parts of phys. blocknr into ext4_fsblk_t */
> +/*
> + * idx_pblock:
> + * combine low and high parts of a leaf physical block number into ext4_fsblk_t
> + */
> static inline ext4_fsblk_t idx_pblock(struct ext4_extent_idx *ix)
> {
> ext4_fsblk_t block;
> @@ -66,7 +72,11 @@ static inline ext4_fsblk_t idx_pblock(st
> return block;
> }
>
> -/* the routine stores large phys. blocknr into extent breaking it into parts */
> +/*
> + * ext4_ext_store_pblock:
> + * stores a large physical block number into an extent struct,
> + * breaking it into parts
> + */
> static inline void ext4_ext_store_pblock(struct ext4_extent *ex, ext4_fsblk_t pb)
> {
> ex->ee_start = cpu_to_le32((unsigned long) (pb & 0xffffffff));
> @@ -74,7 +84,11 @@ static inline void ext4_ext_store_pblock
> ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 0xffff);
> }
>
> -/* the routine stores large phys. blocknr into index breaking it into parts */
> +/*
> + * ext4_idx_store_pblock:
> + * stores a large physical block number into an index struct,
> + * breaking it into parts
> + */
> static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix, ext4_fsblk_t pb)
> {
> ix->ei_leaf = cpu_to_le32((unsigned long) (pb & 0xffffffff));
> @@ -179,8 +193,8 @@ static ext4_fsblk_t ext4_ext_find_goal(s
> if ((ex = path[depth].p_ext))
> return ext_pblock(ex)+(block-le32_to_cpu(ex->ee_block));
>
> - /* it looks index is empty
> - * try to find starting from index itself */
> + /* it looks like index is empty;
> + * try to find starting block from index itself */
> if (path[depth].p_bh)
> return path[depth].p_bh->b_blocknr;
> }
> @@ -317,7 +331,8 @@ static void ext4_ext_drop_refs(struct ex
> }
>
> /*
> - * binary search for closest index by given block
> + * ext4_ext_binsearch_idx:
> + * binary search for the closest index of the given block
> */
> static void
> ext4_ext_binsearch_idx(struct inode *inode, struct ext4_ext_path *path, int block)
> @@ -375,7 +390,8 @@ ext4_ext_binsearch_idx(struct inode *ino
> }
>
> /*
> - * binary search for closest extent by given block
> + * ext4_ext_binsearch:
> + * binary search for closest extent of the given block
> */
> static void
> ext4_ext_binsearch(struct inode *inode, struct ext4_ext_path *path, int block)
> @@ -388,8 +404,8 @@ ext4_ext_binsearch(struct inode *inode,
>
> if (eh->eh_entries == 0) {
> /*
> - * this leaf is empty yet:
> - * we get such a leaf in split/add case
> + * this leaf is empty:
> + * we get such a leaf in split/add case
> */
> return;
> }
> @@ -520,8 +536,9 @@ err:
> }
>
> /*
> - * insert new index [logical;ptr] into the block at cupr
> - * it check where to insert: before curp or after curp
> + * ext4_ext_insert_index:
> + * insert new index [@logical;@ptr] into the block at @curp;
> + * check where to insert: before @curp or after @curp
> */
> static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
> struct ext4_ext_path *curp,
> @@ -574,13 +591,14 @@ static int ext4_ext_insert_index(handle_
> }
>
> /*
> - * routine inserts new subtree into the path, using free index entry
> - * at depth 'at:
> - * - allocates all needed blocks (new leaf and all intermediate index blocks)
> - * - makes decision where to split
> - * - moves remaining extens and index entries (right to the split point)
> - * into the newly allocated blocks
> - * - initialize subtree
> + * ext4_ext_split:
> + * inserts new subtree into the path, using free index entry
> + * at depth @at:
> + * - allocates all needed blocks (new leaf and all intermediate index blocks)
> + * - makes decision where to split
> + * - moves remaining extents and index entries (right to the split point)
> + * into the newly allocated blocks
> + * - initializes subtree
> */
> static int ext4_ext_split(handle_t *handle, struct inode *inode,
> struct ext4_ext_path *path,
> @@ -598,14 +616,14 @@ static int ext4_ext_split(handle_t *hand
> int err = 0;
>
> /* make decision: where to split? */
> - /* FIXME: now desicion is simplest: at current extent */
> + /* FIXME: now decision is simplest: at current extent */
>
> - /* if current leaf will be splitted, then we should use
> + /* if current leaf will be split, then we should use
> * border from split point */
> BUG_ON(path[depth].p_ext > EXT_MAX_EXTENT(path[depth].p_hdr));
> if (path[depth].p_ext != EXT_MAX_EXTENT(path[depth].p_hdr)) {
> border = path[depth].p_ext[1].ee_block;
> - ext_debug("leaf will be splitted."
> + ext_debug("leaf will be split."
> " next leaf starts at %d\n",
> le32_to_cpu(border));
> } else {
> @@ -616,16 +634,16 @@ static int ext4_ext_split(handle_t *hand
> }
>
> /*
> - * if error occurs, then we break processing
> - * and turn filesystem read-only. so, index won't
> + * If error occurs, then we break processing
> + * and mark filesystem read-only. index won't
> * be inserted and tree will be in consistent
> - * state. next mount will repair buffers too
> + * state. Next mount will repair buffers too.
> */
>
> /*
> - * get array to track all allocated blocks
> - * we need this to handle errors and free blocks
> - * upon them
> + * Get array to track all allocated blocks.
> + * We need this to handle errors and free blocks
> + * upon them.
> */
> ablocks = kmalloc(sizeof(ext4_fsblk_t) * depth, GFP_NOFS);
> if (!ablocks)
> @@ -661,7 +679,7 @@ static int ext4_ext_split(handle_t *hand
> neh->eh_depth = 0;
> ex = EXT_FIRST_EXTENT(neh);
>
> - /* move remain of path[depth] to the new leaf */
> + /* move remainder of path[depth] to the new leaf */
> BUG_ON(path[depth].p_hdr->eh_entries != path[depth].p_hdr->eh_max);
> /* start copy from next extent */
> /* TODO: we could do it by single memmove */
> @@ -813,11 +831,12 @@ cleanup:
> }
>
> /*
> - * routine implements tree growing procedure:
> - * - allocates new block
> - * - moves top-level data (index block or leaf) into the new block
> - * - initialize new top-level, creating index that points to the
> - * just created block
> + * ext4_ext_grow_indepth:
> + * implements tree growing procedure:
> + * - allocates new block
> + * - moves top-level data (index block or leaf) into the new block
> + * - initializes new top-level, creating index that points to the
> + * just created block
> */
> static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
> struct ext4_ext_path *path,
> @@ -892,8 +911,9 @@ out:
> }
>
> /*
> - * routine finds empty index and adds new leaf. if no free index found
> - * then it requests in-depth growing
> + * ext4_ext_create_new_leaf:
> + * finds empty index and adds new leaf.
> + * 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,
> struct ext4_ext_path *path,
> @@ -912,8 +932,8 @@ repeat:
> curp--;
> }
>
> - /* we use already allocated block for index block
> - * so, subsequent data blocks should be contigoues */
> + /* we use already allocated block for index block,
> + * so subsequent data blocks should be contiguous */
> 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 */
> @@ -943,12 +963,12 @@ repeat:
> }
>
> /*
> - * only first (depth 0 -> 1) produces free space
> - * in all other cases we have to split growed tree
> + * only first (depth 0 -> 1) produces free space;
> + * in all other cases we have to split the grown tree
> */
> depth = ext_depth(inode);
> if (path[depth].p_hdr->eh_entries == path[depth].p_hdr->eh_max) {
> - /* now we need split */
> + /* now we need to split */
> goto repeat;
> }
> }
> @@ -958,10 +978,11 @@ out:
> }
>
> /*
> - * returns allocated block in subsequent extent or EXT_MAX_BLOCK
> - * NOTE: it consider block number from index entry as
> - * allocated block. thus, index entries have to be consistent
> - * with leafs
> + * ext4_ext_next_allocated_block:
> + * returns allocated block in subsequent extent or EXT_MAX_BLOCK.
> + * NOTE: it considers block number from index entry as
> + * allocated block. Thus, index entries have to be consistent
> + * with leaves.
> */
> static unsigned long
> ext4_ext_next_allocated_block(struct ext4_ext_path *path)
> @@ -993,6 +1014,7 @@ ext4_ext_next_allocated_block(struct ext
> }
>
> /*
> + * ext4_ext_next_leaf_block:
> * returns first allocated block from next leaf or EXT_MAX_BLOCK
> */
> static unsigned ext4_ext_next_leaf_block(struct inode *inode,
> @@ -1021,8 +1043,9 @@ static unsigned ext4_ext_next_leaf_block
> }
>
> /*
> - * if leaf gets modified and modified extent is first in the leaf
> - * then we have to correct all indexes above
> + * ext4_ext_correct_indexes:
> + * if leaf gets modified and modified extent is first in the leaf,
> + * then we have to correct all indexes above.
> * TODO: do we need to correct tree in all cases?
> */
> int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
> @@ -1050,7 +1073,7 @@ int ext4_ext_correct_indexes(handle_t *h
> }
>
> /*
> - * TODO: we need correction if border is smaller then current one
> + * TODO: we need correction if border is smaller than current one
> */
> k = depth - 1;
> border = path[depth].p_ext->ee_block;
> @@ -1085,7 +1108,7 @@ ext4_can_extents_be_merged(struct inode
> /*
> * To allow future support for preallocated extents to be added
> * as an RO_COMPAT feature, refuse to merge to extents if
> - * can result in the top bit of ee_len being set
> + * this can result in the top bit of ee_len being set.
> */
> if (le16_to_cpu(ex1->ee_len) + le16_to_cpu(ex2->ee_len) > EXT_MAX_LEN)
> return 0;
> @@ -1100,9 +1123,10 @@ ext4_can_extents_be_merged(struct inode
> }
>
> /*
> - * this routine tries to merge requsted extent into the existing
> - * extent or inserts requested extent as new one into the tree,
> - * creating new leaf in no-space case
> + * ext4_ext_insert_extent:
> + * tries to merge requsted extent into the existing extent or
> + * inserts requested extent as new one into the tree,
> + * creating new leaf in the no-space case.
> */
> int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
> struct ext4_ext_path *path,
> @@ -1163,8 +1187,8 @@ repeat:
> }
>
> /*
> - * there is no free space in found leaf
> - * we're gonna add new leaf in the tree
> + * There is no free space in the found leaf.
> + * We're gonna add a new leaf in the tree.
> */
> err = ext4_ext_create_new_leaf(handle, inode, path, newext);
> if (err)
> @@ -1377,7 +1401,8 @@ ext4_ext_put_in_cache(struct inode *inod
> }
>
> /*
> - * this routine calculate boundaries of the gap requested block fits into
> + * ext4_ext_put_gap_in_cache:
> + * calculate boundaries of the gap that the requested block fits into
> * and cache this gap
> */
> static inline void
> @@ -1452,9 +1477,10 @@ ext4_ext_in_cache(struct inode *inode, u
> }
>
> /*
> - * routine removes index from the index block
> - * it's used in truncate case only. thus all requests are for
> - * last index in the block only
> + * ext4_ext_rm_idx:
> + * removes index from the index block.
> + * It's used in truncate case only, thus all requests are for
> + * last index in the block only.
> */
> int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
> struct ext4_ext_path *path)
> @@ -1480,11 +1506,12 @@ int ext4_ext_rm_idx(handle_t *handle, st
> }
>
> /*
> - * This routine returns max. credits extent tree can consume.
> + * ext4_ext_calc_credits_for_insert:
> + * This routine returns max. credits that the extent tree can consume.
> * It should be OK for low-performance paths like ->writepage()
> - * To allow many writing process to fit a single transaction,
> - * caller should calculate credits under truncate_mutex and
> - * pass actual path.
> + * To allow many writing processes to fit into a single transaction,
> + * the caller should calculate credits under truncate_mutex and
> + * pass the actual path.
> */
> int inline ext4_ext_calc_credits_for_insert(struct inode *inode,
> struct ext4_ext_path *path)
> @@ -1500,9 +1527,9 @@ int inline ext4_ext_calc_credits_for_ins
> }
>
> /*
> - * given 32bit logical block (4294967296 blocks), max. tree
> + * given 32-bit logical block (4294967296 blocks), max. tree
> * can be 4 levels in depth -- 4 * 340^4 == 53453440000.
> - * let's also add one more level for imbalance.
> + * Let's also add one more level for imbalance.
> */
> depth = 5;
>
> @@ -1510,13 +1537,13 @@ int inline ext4_ext_calc_credits_for_ins
> needed = 2;
>
> /*
> - * tree can be full, so it'd need to grow in depth:
> + * tree can be full, so it would need to grow in depth:
> * allocation + old root + new root
> */
> needed += 2 + 1 + 1;
>
> /*
> - * Index split can happen, we'd need:
> + * Index split can happen, we would need:
> * allocate intermediate indexes (bitmap + group)
> * + change two blocks at each level, but root (already included)
> */
> @@ -1634,7 +1661,7 @@ ext4_ext_rm_leaf(handle_t *handle, struc
> BUG_ON(b != ex_ee_block + ex_ee_len - 1);
> }
>
> - /* at present, extent can't cross block group */
> + /* at present, extent can't cross block group: */
> /* leaf + bitmap + group desc + sb + inode */
> credits = 5;
> if (ex == EXT_FIRST_EXTENT(eh)) {
> @@ -1660,7 +1687,7 @@ ext4_ext_rm_leaf(handle_t *handle, struc
> goto out;
>
> if (num == 0) {
> - /* this extent is removed entirely mark slot unused */
> + /* this extent is removed; mark slot entirely unused */
> ext4_ext_store_pblock(ex, 0);
> eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries)-1);
> }
> @@ -1692,7 +1719,8 @@ out:
> }
>
> /*
> - * returns 1 if current index have to be freed (even partial)
> + * ext4_ext_more_to_rm:
> + * returns 1 if current index has to be freed (even partial)
> */
> static int inline
> ext4_ext_more_to_rm(struct ext4_ext_path *path)
> @@ -1703,7 +1731,7 @@ ext4_ext_more_to_rm(struct ext4_ext_path
> return 0;
>
> /*
> - * if truncate on deeper level happened it it wasn't partial
> + * if truncate on deeper level happened, it wasn't partial,
> * so we have to consider current index for truncation
> */
> if (le16_to_cpu(path->p_hdr->eh_entries) == path->p_block)
> @@ -1729,8 +1757,8 @@ int ext4_ext_remove_space(struct inode *
> ext4_ext_invalidate_cache(inode);
>
> /*
> - * we start scanning from right side freeing all the blocks
> - * after i_size and walking into the deep
> + * We start scanning from right side, freeing all the blocks
> + * after i_size and walking into the tree depth-wise.
> */
> path = kmalloc(sizeof(struct ext4_ext_path) * (depth + 1), GFP_KERNEL);
> if (path == NULL) {
> @@ -1749,7 +1777,7 @@ int ext4_ext_remove_space(struct inode *
> if (i == depth) {
> /* this is leaf block */
> err = ext4_ext_rm_leaf(handle, inode, path, start);
> - /* root level have p_bh == NULL, brelse() eats this */
> + /* root level has p_bh == NULL, brelse() eats this */
> brelse(path[i].p_bh);
> path[i].p_bh = NULL;
> i--;
> @@ -1772,14 +1800,14 @@ int ext4_ext_remove_space(struct inode *
> BUG_ON(path[i].p_hdr->eh_magic != EXT4_EXT_MAGIC);
>
> if (!path[i].p_idx) {
> - /* this level hasn't touched yet */
> + /* this level hasn't been touched yet */
> path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
> path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries)+1;
> ext_debug("init index ptr: hdr 0x%p, num %d\n",
> path[i].p_hdr,
> le16_to_cpu(path[i].p_hdr->eh_entries));
> } else {
> - /* we've already was here, see at next index */
> + /* we were already here, see at next index */
> path[i].p_idx--;
> }
>
> @@ -1799,19 +1827,19 @@ int ext4_ext_remove_space(struct inode *
> break;
> }
>
> - /* put actual number of indexes to know is this
> - * number got changed at the next iteration */
> + /* save actual number of indexes since this
> + * number is changed at the next iteration */
> path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries);
> i++;
> } else {
> - /* we finish processing this index, go up */
> + /* we finished processing this index, go up */
> if (path[i].p_hdr->eh_entries == 0 && i > 0) {
> - /* index is empty, remove it
> + /* index is empty, remove it;
> * handle must be already prepared by the
> * truncatei_leaf() */
> err = ext4_ext_rm_idx(handle, inode, path + i);
> }
> - /* root level have p_bh == NULL, brelse() eats this */
> + /* root level has p_bh == NULL, brelse() eats this */
> brelse(path[i].p_bh);
> path[i].p_bh = NULL;
> i--;
> @@ -1822,8 +1850,8 @@ int ext4_ext_remove_space(struct inode *
> /* TODO: flexible tree reduction should be here */
> if (path->p_hdr->eh_entries == 0) {
> /*
> - * truncate to zero freed all the tree
> - * so, we need to correct eh_depth
> + * truncate to zero freed all the tree,
> + * so we need to correct eh_depth
> */
> err = ext4_ext_get_access(handle, inode, path);
> if (err == 0) {
> @@ -1911,7 +1939,7 @@ int ext4_ext_get_blocks(handle_t *handle
> if (goal == EXT4_EXT_CACHE_GAP) {
> if (!create) {
> /* block isn't allocated yet and
> - * user don't want to allocate it */
> + * user doesn't want to allocate it */
> goto out2;
> }
> /* we should allocate requested block */
> @@ -1920,7 +1948,7 @@ int ext4_ext_get_blocks(handle_t *handle
> newblock = iblock
> - le32_to_cpu(newex.ee_block)
> + ext_pblock(&newex);
> - /* number of remain blocks in the extent */
> + /* number of remaining blocks in the extent */
> allocated = le16_to_cpu(newex.ee_len) -
> (iblock - le32_to_cpu(newex.ee_block));
> goto out;
> @@ -1940,8 +1968,8 @@ int ext4_ext_get_blocks(handle_t *handle
> depth = ext_depth(inode);
>
> /*
> - * consistent leaf must not be empty
> - * this situations is possible, though, _during_ tree modification
> + * consistent leaf must not be empty;
> + * this situation is possible, though, _during_ tree modification;
> * this is why assert can't be put in ext4_ext_find_extent()
> */
> BUG_ON(path[depth].p_ext == NULL && depth != 0);
> @@ -1959,10 +1987,10 @@ int ext4_ext_get_blocks(handle_t *handle
> */
> if (ee_len > EXT_MAX_LEN)
> goto out2;
> - /* if found exent covers block, simple return it */
> + /* if found extent covers block, simply return it */
> if (iblock >= ee_block && iblock < ee_block + ee_len) {
> newblock = iblock - ee_block + ee_start;
> - /* number of remain blocks in the extent */
> + /* number of remaining blocks in the extent */
> allocated = ee_len - (iblock - ee_block);
> ext_debug("%d fit into %lu:%d -> "E3FSBLK"\n", (int) iblock,
> ee_block, ee_len, newblock);
> @@ -1973,17 +2001,18 @@ int ext4_ext_get_blocks(handle_t *handle
> }
>
> /*
> - * requested block isn't allocated yet
> + * requested block isn't allocated yet;
> * we couldn't try to create block if create flag is zero
> */
> if (!create) {
> - /* put just found gap into cache to speedup subsequest reqs */
> + /* put just found gap into cache to speed up
> + * subsequent requests */
> ext4_ext_put_gap_in_cache(inode, path, iblock);
> goto out2;
> }
> /*
> * Okay, we need to do block allocation. Lazily initialize the block
> - * allocation info here if necessary
> + * allocation info here if necessary.
> */
> if (S_ISREG(inode->i_mode) && (!EXT4_I(inode)->i_block_alloc_info))
> ext4_init_block_alloc_info(inode);
> @@ -2061,9 +2090,9 @@ void ext4_ext_truncate(struct inode * in
> ext4_ext_invalidate_cache(inode);
>
> /*
> - * TODO: optimization is possible here
> - * probably we need not scaning at all,
> - * because page truncation is enough
> + * TODO: optimization is possible here.
> + * Probably we need not scan at all,
> + * because page truncation is enough.
> */
> if (ext4_orphan_add(handle, inode))
> goto out_stop;
> @@ -2077,13 +2106,13 @@ void ext4_ext_truncate(struct inode * in
> err = ext4_ext_remove_space(inode, last_block);
>
> /* In a multi-transaction truncate, we only make the final
> - * transaction synchronous */
> + * transaction synchronous. */
> if (IS_SYNC(inode))
> handle->h_sync = 1;
>
> out_stop:
> /*
> - * If this was a simple ftruncate(), and the file will remain alive
> + * If this was a simple ftruncate() and the file will remain alive,
> * then we need to clear up the orphan record which we created above.
> * However, if this was a real unlink then we were called by
> * ext4_delete_inode(), and we allow that function to clean up the
> @@ -2097,7 +2126,8 @@ out_stop:
> }
>
> /*
> - * this routine calculate max number of blocks we could modify
> + * ext4_ext_writepage_trans_blocks:
> + * calculate max number of blocks we could modify
> * in order to allocate new block for an inode
> */
> int ext4_ext_writepage_trans_blocks(struct inode *inode, int num)
> @@ -2106,7 +2136,7 @@ int ext4_ext_writepage_trans_blocks(stru
>
> needed = ext4_ext_calc_credits_for_insert(inode, NULL);
>
> - /* caller want to allocate num blocks, but note it includes sb */
> + /* caller wants to allocate num blocks, but note it includes sb */
> needed = needed * num - (num - 1);
>
> #ifdef CONFIG_QUOTA
> -
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