Message-ID: <CAD+ocbwgH6bHrPqB0ERM2YA703nASqRzLYCu-eJQn1uFgh1ivg@mail.gmail.com>
Date:   Wed, 16 Jan 2019 12:51:18 -0800
From:   harshad shirwadkar <harshadshirwadkar@...il.com>
To:     Alexey Lyashkov <umka@...udlinux.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: shrink directory when last block is empty

Hi Alexey,

Thanks, yes that's a good point. I'll incorporate it and send another patch.

- Harshad.


On Wed, Jan 16, 2019 at 6:28 AM Alexey Lyashkov <umka@...udlinux.com> wrote:
>
> Hi Harshad,
>
> I quickly look to the patch, but as i see you have called a count_dentries - it have called on each delete entry.
> If you have lots create/delete in loop for one block it’s costly and decrease a delete performance.
> as i see it have used just for checking against zero, so can it be replaced with more simple check like is first dir entry cover a whole block ?
>
>
> > 16 янв. 2019 г., в 1:55, harshadshirwadkar@...il.com написал(а):
> >
> > From: Harshad Shirwadkar <harshadshirwadkar@...il.com>
> >
> > This patch is the first step towards shrinking htree based directories
> > when files are deleted. We truncate directory inode when a directory
> > entry removal causes last directory block to be empty. This patch just
> > removes the last block. We may end up in a situation where many
> > intermediate dirent blocks in directory inode are empty. Removing
> > those blocks would be handled later.
> >
> > Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>
> > ---
> > fs/ext4/namei.c | 146 +++++++++++++++++++++++++++++++++++++++++-------
> > 1 file changed, 125 insertions(+), 21 deletions(-)
> >
> > diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> > index 2a4c25c4681d..bbcbd59c44ce 100644
> > --- a/fs/ext4/namei.c
> > +++ b/fs/ext4/namei.c
> > @@ -273,7 +273,8 @@ static int ext4_htree_next_block(struct inode *dir, __u32 hash,
> >                                __u32 *start_hash);
> > static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
> >               struct ext4_filename *fname,
> > -             struct ext4_dir_entry_2 **res_dir);
> > +             struct ext4_dir_entry_2 **res_dir,
> > +             struct dx_frame *dx_frame);
> > static int ext4_dx_add_entry(handle_t *handle, struct ext4_filename *fname,
> >                            struct inode *dir, struct inode *inode);
> >
> > @@ -380,6 +381,7 @@ static void ext4_dirent_csum_set(struct inode *inode,
> >                                          (void *)t - (void *)dirent);
> > }
> >
> > +
> > int ext4_handle_dirty_dirent_node(handle_t *handle,
> >                                 struct inode *inode,
> >                                 struct buffer_head *bh)
> > @@ -797,7 +799,7 @@ dx_probe(struct ext4_filename *fname, struct inode *dir,
> >       dxtrace(printk("Look up %x", hash));
> >       while (1) {
> >               count = dx_get_count(entries);
> > -             if (!count || count > dx_get_limit(entries)) {
> > +             if (count > dx_get_limit(entries)) {
> >                       ext4_warning_inode(dir,
> >                                          "dx entry: count %u beyond limit %u",
> >                                          count, dx_get_limit(entries));
> > @@ -866,6 +868,42 @@ dx_probe(struct ext4_filename *fname, struct inode *dir,
> >       return ret_err;
> > }
> >
> > +static void
> > +ext4_dx_delete_entry(handle_t *handle, struct inode *dir,
> > +                  struct dx_frame *dx_frame, __le64 block)
> > +{
> > +     struct dx_entry *entries;
> > +     unsigned int count, limit;
> > +     int err, i;
> > +
> > +     entries = dx_frame->entries;
> > +     count = dx_get_count(entries);
> > +     limit = dx_get_limit(entries);
> > +
> > +     for (i = 0; i < count; i++)
> > +             if (entries[i].block == block)
> > +                     break;
> > +
> > +     if (i >= count)
> > +             return;
> > +
> > +     err = ext4_journal_get_write_access(handle, dx_frame->bh);
> > +     if (err) {
> > +             ext4_std_error(dir->i_sb, err);
> > +             return;
> > +     }
> > +
> > +     for (; i < count - 1; i++)
> > +             entries[i] = entries[i + 1];
> > +
> > +     dx_set_count(entries, count - 1);
> > +     dx_set_limit(entries, limit);
> > +
> > +     err = ext4_handle_dirty_dx_node(handle, dir, dx_frame->bh);
> > +     if (err)
> > +             ext4_std_error(dir->i_sb, err);
> > +}
> > +
> > static void dx_release(struct dx_frame *frames)
> > {
> >       struct dx_root_info *info;
> > @@ -1309,6 +1347,28 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
> >       return 0;
> > }
> >
> > +static int count_dentries(char *search_buf, int buf_size,
> > +                       unsigned int blocksize)
> > +{
> > +     struct ext4_dir_entry_2 *de;
> > +     char *dlimit;
> > +     int de_len;
> > +     int count = 0;
> > +
> > +     de = (struct ext4_dir_entry_2 *)search_buf;
> > +     dlimit = search_buf + buf_size;
> > +     while ((char *)de < dlimit) {
> > +             de_len = ext4_rec_len_from_disk(de->rec_len, blocksize);
> > +             if (de_len <= 0)
> > +                     return count;
> > +             if (de->inode != 0)
> > +                     count++;
> > +             de = (struct ext4_dir_entry_2 *)((char *)de + de_len);
> > +     }
> > +
> > +     return count;
> > +}
> > +
> > static int is_dx_internal_node(struct inode *dir, ext4_lblk_t block,
> >                              struct ext4_dir_entry *de)
> > {
> > @@ -1339,7 +1399,8 @@ static int is_dx_internal_node(struct inode *dir, ext4_lblk_t block,
> > static struct buffer_head * ext4_find_entry (struct inode *dir,
> >                                       const struct qstr *d_name,
> >                                       struct ext4_dir_entry_2 **res_dir,
> > -                                     int *inlined)
> > +                                     int *inlined,
> > +                                     struct dx_frame *dx_frame)
> > {
> >       struct super_block *sb;
> >       struct buffer_head *bh_use[NAMEI_RA_SIZE];
> > @@ -1388,7 +1449,7 @@ static struct buffer_head * ext4_find_entry (struct inode *dir,
> >               goto restart;
> >       }
> >       if (is_dx(dir)) {
> > -             ret = ext4_dx_find_entry(dir, &fname, res_dir);
> > +             ret = ext4_dx_find_entry(dir, &fname, res_dir, dx_frame);
> >               /*
> >                * On success, or if the error was file not found,
> >                * return.  Otherwise, fall back to doing a search the
> > @@ -1486,9 +1547,10 @@ static struct buffer_head * ext4_find_entry (struct inode *dir,
> >       return ret;
> > }
> >
> > -static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
> > -                     struct ext4_filename *fname,
> > -                     struct ext4_dir_entry_2 **res_dir)
> > +static struct buffer_head *ext4_dx_find_entry(
> > +                     struct inode *dir, struct ext4_filename *fname,
> > +                     struct ext4_dir_entry_2 **res_dir,
> > +                     struct dx_frame *dx_frame)
> > {
> >       struct super_block * sb = dir->i_sb;
> >       struct dx_frame frames[EXT4_HTREE_LEVEL], *frame;
> > @@ -1502,6 +1564,10 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
> >       frame = dx_probe(fname, dir, NULL, frames);
> >       if (IS_ERR(frame))
> >               return (struct buffer_head *) frame;
> > +     if (dx_frame) {
> > +             *dx_frame = *frame;
> > +             get_bh(dx_frame->bh);
> > +     }
> >       do {
> >               block = dx_get_block(frame->at);
> >               bh = ext4_read_dirblock(dir, block, DIRENT);
> > @@ -1553,7 +1619,7 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
> >       if (dentry->d_name.len > EXT4_NAME_LEN)
> >               return ERR_PTR(-ENAMETOOLONG);
> >
> > -     bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
> > +     bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL, NULL);
> >       if (IS_ERR(bh))
> >               return (struct dentry *) bh;
> >       inode = NULL;
> > @@ -1597,7 +1663,7 @@ struct dentry *ext4_get_parent(struct dentry *child)
> >       struct ext4_dir_entry_2 * de;
> >       struct buffer_head *bh;
> >
> > -     bh = ext4_find_entry(d_inode(child), &dotdot, &de, NULL);
> > +     bh = ext4_find_entry(d_inode(child), &dotdot, &de, NULL, NULL);
> >       if (IS_ERR(bh))
> >               return (struct dentry *) bh;
> >       if (!bh)
> > @@ -2337,9 +2403,13 @@ int ext4_generic_delete_entry(handle_t *handle,
> > static int ext4_delete_entry(handle_t *handle,
> >                            struct inode *dir,
> >                            struct ext4_dir_entry_2 *de_del,
> > -                          struct buffer_head *bh)
> > +                          struct buffer_head *bh,
> > +                          struct dx_frame *dx_frame)
> > {
> > +     struct ext4_map_blocks map;
> >       int err, csum_size = 0;
> > +     int should_truncate = 0;
> > +
> >
> >       if (ext4_has_inline_data(dir)) {
> >               int has_inline_data = 1;
> > @@ -2363,11 +2433,37 @@ static int ext4_delete_entry(handle_t *handle,
> >       if (err)
> >               goto out;
> >
> > +     if (dx_frame && dx_frame->bh &&
> > +         count_dentries(bh->b_data, bh->b_size,
> > +                        dir->i_sb->s_blocksize) == 0) {
> > +
> > +             map.m_lblk = (dir->i_size - 1) >>
> > +                          (dir->i_sb->s_blocksize_bits);
> > +             map.m_len = 1;
> > +             err = ext4_map_blocks(handle, dir, &map, 0);
> > +
> > +             if ((err > 0) && (bh->b_blocknr == map.m_pblk)) {
> > +                     ext4_dx_delete_entry(handle, dir, dx_frame,
> > +                                          cpu_to_le64(map.m_lblk));
> > +                     should_truncate = 1;
> > +             }
> > +     }
> > +
> >       BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
> > +
> >       err = ext4_handle_dirty_dirent_node(handle, dir, bh);
> >       if (unlikely(err))
> >               goto out;
> >
> > +     if (should_truncate) {
> > +             dir->i_size -= dir->i_sb->s_blocksize;
> > +             ext4_truncate(dir);
> > +             if (dir->i_size == dir->i_sb->s_blocksize) {
> > +                     ext4_clear_inode_flag(dir, EXT4_INODE_INDEX);
> > +                     ext4_mark_inode_dirty(handle, dir);
> > +             }
> > +     }
> > +
> >       return 0;
> > out:
> >       if (err != -ENOENT)
> > @@ -2923,7 +3019,7 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
> >               return retval;
> >
> >       retval = -ENOENT;
> > -     bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
> > +     bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL, NULL);
> >       if (IS_ERR(bh))
> >               return PTR_ERR(bh);
> >       if (!bh)
> > @@ -2950,7 +3046,7 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
> >       if (IS_DIRSYNC(dir))
> >               ext4_handle_sync(handle);
> >
> > -     retval = ext4_delete_entry(handle, dir, de, bh);
> > +     retval = ext4_delete_entry(handle, dir, de, bh, NULL);
> >       if (retval)
> >               goto end_rmdir;
> >       if (!EXT4_DIR_LINK_EMPTY(inode))
> > @@ -2985,6 +3081,9 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
> >       struct buffer_head *bh;
> >       struct ext4_dir_entry_2 *de;
> >       handle_t *handle = NULL;
> > +     struct dx_frame dx_frame;
> > +
> > +     memset(&dx_frame, 0, sizeof(dx_frame));
> >
> >       if (unlikely(ext4_forced_shutdown(EXT4_SB(dir->i_sb))))
> >               return -EIO;
> > @@ -3000,7 +3099,7 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
> >               return retval;
> >
> >       retval = -ENOENT;
> > -     bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
> > +     bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL, &dx_frame);
> >       if (IS_ERR(bh))
> >               return PTR_ERR(bh);
> >       if (!bh)
> > @@ -3028,9 +3127,10 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
> >                                  dentry->d_name.len, dentry->d_name.name);
> >               set_nlink(inode, 1);
> >       }
> > -     retval = ext4_delete_entry(handle, dir, de, bh);
> > +     retval = ext4_delete_entry(handle, dir, de, bh, &dx_frame);
> >       if (retval)
> >               goto end_unlink;
> > +
> >       dir->i_ctime = dir->i_mtime = current_time(dir);
> >       ext4_update_dx_flag(dir);
> >       ext4_mark_inode_dirty(handle, dir);
> > @@ -3042,6 +3142,8 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
> >
> > end_unlink:
> >       brelse(bh);
> > +     if (dx_frame.bh)
> > +             brelse(dx_frame.bh);
> >       if (handle)
> >               ext4_journal_stop(handle);
> >       trace_ext4_unlink_exit(dentry, retval);
> > @@ -3362,11 +3464,11 @@ static int ext4_find_delete_entry(handle_t *handle, struct inode *dir,
> >       struct buffer_head *bh;
> >       struct ext4_dir_entry_2 *de;
> >
> > -     bh = ext4_find_entry(dir, d_name, &de, NULL);
> > +     bh = ext4_find_entry(dir, d_name, &de, NULL, NULL);
> >       if (IS_ERR(bh))
> >               return PTR_ERR(bh);
> >       if (bh) {
> > -             retval = ext4_delete_entry(handle, dir, de, bh);
> > +             retval = ext4_delete_entry(handle, dir, de, bh, NULL);
> >               brelse(bh);
> >       }
> >       return retval;
> > @@ -3390,7 +3492,8 @@ static void ext4_rename_delete(handle_t *handle, struct ext4_renament *ent,
> >               retval = ext4_find_delete_entry(handle, ent->dir,
> >                                               &ent->dentry->d_name);
> >       } else {
> > -             retval = ext4_delete_entry(handle, ent->dir, ent->de, ent->bh);
> > +             retval = ext4_delete_entry(handle, ent->dir, ent->de, ent->bh,
> > +                                        NULL);
> >               if (retval == -ENOENT) {
> >                       retval = ext4_find_delete_entry(handle, ent->dir,
> >                                                       &ent->dentry->d_name);
> > @@ -3497,7 +3600,8 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> >                       return retval;
> >       }
> >
> > -     old.bh = ext4_find_entry(old.dir, &old.dentry->d_name, &old.de, NULL);
> > +     old.bh = ext4_find_entry(old.dir, &old.dentry->d_name, &old.de, NULL,
> > +                              NULL);
> >       if (IS_ERR(old.bh))
> >               return PTR_ERR(old.bh);
> >       /*
> > @@ -3511,7 +3615,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> >               goto end_rename;
> >
> >       new.bh = ext4_find_entry(new.dir, &new.dentry->d_name,
> > -                              &new.de, &new.inlined);
> > +                              &new.de, &new.inlined, NULL);
> >       if (IS_ERR(new.bh)) {
> >               retval = PTR_ERR(new.bh);
> >               new.bh = NULL;
> > @@ -3691,7 +3795,7 @@ static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
> >               return retval;
> >
> >       old.bh = ext4_find_entry(old.dir, &old.dentry->d_name,
> > -                              &old.de, &old.inlined);
> > +                              &old.de, &old.inlined, NULL);
> >       if (IS_ERR(old.bh))
> >               return PTR_ERR(old.bh);
> >       /*
> > @@ -3705,7 +3809,7 @@ static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
> >               goto end_rename;
> >
> >       new.bh = ext4_find_entry(new.dir, &new.dentry->d_name,
> > -                              &new.de, &new.inlined);
> > +                              &new.de, &new.inlined, NULL);
> >       if (IS_ERR(new.bh)) {
> >               retval = PTR_ERR(new.bh);
> >               new.bh = NULL;
> > --
> > 2.20.1.97.g81188d93c3-goog
> >
>

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