Hi Jaegeuk,
> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaeg...@kernel.org]
> Sent: Thursday, December 24, 2015 10:15 AM
> To: linux-kernel@vger.kernel.org; linux-fsde...@vger.kernel.org;
> linux-f2fs-de...@lists.sourceforge.net
> Cc: Jaegeuk Kim
> Subject: [f2fs-dev] [PATCH 3/4] f2fs: avoid f2fs_lock_op in f2fs_write_begin
>
> If f2fs_write_begin is to update data, we can bypass calling f2fs_lock_op() in
> order to avoid the checkpoint latency in the write syscall.
>
> Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
> ---
> fs/f2fs/data.c | 43 ++++++++++++++++++++++++++++++++++---------
> 1 file changed, 34 insertions(+), 9 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 49092da..d53cf4f 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1418,10 +1418,16 @@ static int prepare_write_begin(struct f2fs_sb_info
> *sbi,
> pgoff_t index = page->index;
> struct dnode_of_data dn;
> struct page *ipage;
> + bool locked = false;
> + struct extent_info ei;
> int err = 0;
>
> - f2fs_lock_op(sbi);
> -
> + if (f2fs_has_inline_data(inode) ||
> + (pos & PAGE_CACHE_MASK) >= i_size_read(inode)) {
> + f2fs_lock_op(sbi);
> + locked = true;
> + }
> +restart:
> /* check inline_data */
> ipage = get_node_page(sbi, inode->i_ino);
> if (IS_ERR(ipage)) {
> @@ -1436,22 +1442,41 @@ static int prepare_write_begin(struct f2fs_sb_info
> *sbi,
> read_inline_data(page, ipage);
> set_inode_flag(F2FS_I(inode), FI_DATA_EXIST);
> sync_inode_page(&dn);
> - goto done;
> } else {
> err = f2fs_convert_inline_page(&dn, page);
> if (err)
> - goto err_out;
> + goto out;
> + err = f2fs_get_block(&dn, index);
Seems after f2fs_convert_inline_page, data_blkaddr and node_changed should
have been set, so f2fs_get_block could be removed here.
> + }
> + } else if (locked) {
> + err = f2fs_get_block(&dn, index);
> + } else {
> + if (f2fs_lookup_extent_cache(inode, index, &ei)) {
> + dn.data_blkaddr = ei.blk + index - ei.fofs;
> + } else {
> + bool restart = false;
> +
> + /* hole case */
> + err = get_dnode_of_data(&dn, index, LOOKUP_NODE);
Better to handle error case like -ENOMEM or -EIO.
Thanks,
> + if (err || (!err && dn.data_blkaddr == NULL_ADDR))
> + restart = true;
> + if (restart) {
> + f2fs_put_dnode(&dn);
> + f2fs_lock_op(sbi);
> + locked = true;
> + goto restart;
> + }
> }
> }
> - err = f2fs_get_block(&dn, index);
> -done:
> +
> /* convert_inline_page can make node_changed */
> *blk_addr = dn.data_blkaddr;
> *node_changed = dn.node_changed;
> -err_out:
> +out:
> f2fs_put_dnode(&dn);
> unlock_out:
> - f2fs_unlock_op(sbi);
> + if (locked)
> + f2fs_unlock_op(sbi);
> return err;
> }
>
> @@ -1488,7 +1513,7 @@ repeat:
>
> *pagep = page;
>
> - err = prepare_write_begin(sbi, page, pos + len,
> + err = prepare_write_begin(sbi, page, pos, len,
> &blkaddr, &need_balance);
> if (err)
> goto fail;
> --
> 2.5.4 (Apple Git-61)
>
>
> ------------------------------------------------------------------------------
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