[Ocfs2-devel] [PATCH 1/1] Ocfs2: Optimize punching-hole codes v3.
Tao Ma
tao.ma at oracle.com
Mon Mar 29 23:56:39 PDT 2010
Hi Tristan,
here comes the review.
Tristan Ye wrote:
> Changes from v2 to v3:
>
<snip>
> +/*
> + * Hepler to find the rightmost record which contains 'pos' cpos,
> + * skip the holes if any, also adjust the 'pos' accordingly.
You don't mentioned what 'pos' indicates here, so it is very hard to
read this function and I have to guess. ;) So please describe it in detail.
> + */
> +static void ocfs2_find_rec_with_pos(struct ocfs2_extent_list *el,
> + struct ocfs2_extent_rec **rec_got,
> + u32 *pos)
> +{
> + int i;
> + u32 range;
> + struct ocfs2_extent_rec *rec = NULL;
> +
> + for (i = le16_to_cpu(el->l_next_free_rec) - 1; i >= 0; i--) {
> +
> + rec = &el->l_recs[i];
> + range = le32_to_cpu(rec->e_cpos) +
> + ocfs2_rec_clusters(el, rec);
> +
> + if (le32_to_cpu(rec->e_cpos) < *pos) {
> + /*
> + * Skip a hole.
> + */
> + if (range < *pos)
> + *pos = range;
> +
> + break;
> + }
> +
> + /*
> + * Simply jump to previous record if the pos is
> + * the start of a record.
> + */
> + if (le32_to_cpu(rec->e_cpos) == *pos) {
> + i--;
> + if (i < 0) {
> + *rec_got = NULL;
> + return;
> + }
> +
> + rec = &el->l_recs[i];
> + range = le32_to_cpu(rec->e_cpos) +
> + ocfs2_rec_clusters(el, rec);
> + /*
> + * Skip a hole.
> + */
> + if (range < *pos)
> + *pos = range;
do we still need to check range < *pos? As you have already check
le32_to_cpu(rec->e_cpos) == *pos.
> +
> + break;
> + }
> + }
> +
> + *rec_got = &el->l_recs[i];
> +}
> +
> +/*
> + * Helper to calculate the punching pos and length in one run, we handle the
> + * following three cases in order:
> + *
> + * - remove the entire record
> + * - remove a partial record
> + * - no record needs to be removed (hole-punching completed)
> +*/
> +static void ocfs2_calc_trunc_pos(struct inode *inode,
> + struct ocfs2_extent_list *el,
> + struct ocfs2_extent_rec *rec,
> + u32 trunc_start, u32 *trunc_cpos,
> + u32 *trunc_len, u32 *trunc_end,
> + u64 *blkno, int *done)
> +{
> + int ret = 0;
> + u32 coff, range;
> +
> + range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
> +
> + if (le32_to_cpu(rec->e_cpos) >= trunc_start) {
> + *trunc_cpos = le32_to_cpu(rec->e_cpos);
> + *trunc_len = *trunc_end - le32_to_cpu(rec->e_cpos);
> + *blkno = le64_to_cpu(rec->e_blkno);
> + *trunc_end = le32_to_cpu(rec->e_cpos);
> + } else if (range > trunc_start) {
> + *trunc_cpos = trunc_start;
> + *trunc_len = range - trunc_start;
> + coff = trunc_start - le32_to_cpu(rec->e_cpos);
> + *blkno = le64_to_cpu(rec->e_blkno) +
> + ocfs2_clusters_to_blocks(inode->i_sb, coff);
> + *trunc_end = trunc_start;
> + } else {
> + /*
> + * It may have two following possibilities:
> + *
> + * - last record has been removed
what do you mean last record here? Sorry, I don't understand this case.
> + * - trunc_start was within a hole
> + *
> + * both two cases mean the completion of hole punching.
> + */
> + ret = 1;
> + }
> +
> + *done = ret;
> +}
> +
> static int ocfs2_remove_inode_range(struct inode *inode,
> struct buffer_head *di_bh, u64 byte_start,
> u64 byte_len)
> {
> - int ret = 0, flags = 0;
> - u32 trunc_start, trunc_len, cpos, phys_cpos, alloc_size;
> + int ret = 0, flags = 0, done = 0;
> + u32 trunc_start, trunc_len, trunc_end, trunc_cpos, phys_cpos;
> + u32 cluster_within_list;
> struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> struct ocfs2_cached_dealloc_ctxt dealloc;
> struct address_space *mapping = inode->i_mapping;
> struct ocfs2_extent_tree et;
> + struct ocfs2_path *path = NULL;
> + struct ocfs2_extent_list *el = NULL;
> + struct ocfs2_extent_rec *rec = NULL;
> struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
> - u64 refcount_loc = le64_to_cpu(di->i_refcount_loc);
> + u64 blkno, refcount_loc = le64_to_cpu(di->i_refcount_loc);
>
> ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);
> ocfs2_init_dealloc_ctxt(&dealloc);
> @@ -1482,16 +1588,13 @@ static int ocfs2_remove_inode_range(struct inode *inode,
> }
>
> trunc_start = ocfs2_clusters_for_bytes(osb->sb, byte_start);
> - trunc_len = (byte_start + byte_len) >> osb->s_clustersize_bits;
> - if (trunc_len >= trunc_start)
> - trunc_len -= trunc_start;
> - else
> - trunc_len = 0;
> + trunc_end = (byte_start + byte_len) >> osb->s_clustersize_bits;
> + cluster_within_list = trunc_end;
You said in the comments below that "we want to find a path which
contains (trunc_end - 1)". So we also need to set trunc_end -1 here?
Otherwise you may enter the wrong extent block in some case?
>
> - mlog(0, "Inode: %llu, start: %llu, len: %llu, cstart: %u, clen: %u\n",
> + mlog(0, "Inode: %llu, start: %llu, len: %llu, cstart: %u, cend: %u\n",
> (unsigned long long)OCFS2_I(inode)->ip_blkno,
> (unsigned long long)byte_start,
> - (unsigned long long)byte_len, trunc_start, trunc_len);
> + (unsigned long long)byte_len, trunc_start, trunc_end);
>
> ret = ocfs2_zero_partial_clusters(inode, byte_start, byte_len);
> if (ret) {
> @@ -1499,32 +1602,65 @@ static int ocfs2_remove_inode_range(struct inode *inode,
> goto out;
> }
>
> - cpos = trunc_start;
> - while (trunc_len) {
> - ret = ocfs2_get_clusters(inode, cpos, &phys_cpos,
> - &alloc_size, &flags);
> + path = ocfs2_new_path_from_et(&et);
> + if (!path) {
> + ret = -ENOMEM;
> + mlog_errno(ret);
> + goto out;
> + }
> +
> + while (trunc_end > 0) {
I am just curious of this check. trunc_end seems to be a cluster offset.
So how could it be 0 in case we don't punch from the 0 and where do you
set it to 0?
> + /*
> + * Unlike truncate codes, here we want to find a path which
> + * contains (trunc_end - 1) cpos, and then trunc_end will be
> + * decreased after each removal of a record range.
> + *
> + * Why not using trunc_end to search the path?
> + * The reason is simple, think about the situation of crossing
> + * the extent block, we need to find the adjacent block by
> + * decreasing one cluster, otherwise, it will run into a loop.
> + */
> + ret = ocfs2_find_path(INODE_CACHE(inode), path,
> + cluster_within_list);
> if (ret) {
> mlog_errno(ret);
> goto out;
> }
>
> - if (alloc_size > trunc_len)
> - alloc_size = trunc_len;
> + el = path_leaf_el(path);
>
> - /* Only do work for non-holes */
> - if (phys_cpos != 0) {
> - ret = ocfs2_remove_btree_range(inode, &et, cpos,
> - phys_cpos, alloc_size,
> - &dealloc, refcount_loc,
> - flags);
> - if (ret) {
> - mlog_errno(ret);
> - goto out;
> - }
> + ocfs2_find_rec_with_pos(el, &rec, &trunc_end);
> + /*
> + * Go to next extent block directly when last rec was truncated.
> + */
> + if (!rec) {
> + cluster_within_list = trunc_end - 1;
> + ocfs2_reinit_path(path, 1);
> + break;
ocfs2_find_rec_with_pos will find a rec contains trunc_end and if there
is no such rec and trunc_end < el->l_recs[0].e_cpos, rec will be set
NULL, right?
So what if the el is in the left most extent block? Your function will
iterate again and again with every time trunc_end--?
another problem is that your comments is "Go to next extent block
directly when last rec was truncated", I guess you mean 'previous'? And
you 'break' here, so how could the previous extent block get punched?
Am I wrong somehow?
> }
>
> - cpos += alloc_size;
> - trunc_len -= alloc_size;
> + ocfs2_calc_trunc_pos(inode, el, rec, trunc_start, &trunc_cpos,
> + &trunc_len, &trunc_end, &blkno, &done);
> + if (done)
> + break;
> +
> + flags = rec->e_flags;
> + phys_cpos = ocfs2_blocks_to_clusters(inode->i_sb, blkno);
> +
> + ret = ocfs2_remove_btree_range(inode, &et, trunc_cpos,
> + phys_cpos, trunc_len, &dealloc,
> + refcount_loc, flags);
> + if (ret < 0) {
> + mlog_errno(ret);
> + goto out;
> + }
> +
> + if (trunc_end > 0)
> + cluster_within_list = trunc_end - 1;
> + else
> + break;
> +
> + ocfs2_reinit_path(path, 1);
> }
>
> ocfs2_truncate_cluster_pages(inode, byte_start, byte_len);
Regards,
Tao
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