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Message-ID: <62da3bfb-6d50-2eb9-1b9a-13f5287f562d@huaweicloud.com> Date: Wed, 3 Jan 2024 21:20:51 +0800 From: Zhang Yi <yi.zhang@...weicloud.com> To: Jan Kara <jack@...e.cz> Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, ritesh.list@...il.com, hch@...radead.org, djwong@...nel.org, willy@...radead.org, yi.zhang@...wei.com, chengzhihao1@...wei.com, yukuai3@...wei.com, wangkefeng.wang@...wei.com Subject: Re: [RFC PATCH v2 05/25] ext4: make ext4_map_blocks() distinguish delalloc only extent On 2024/1/3 19:31, Jan Kara wrote: > On Tue 02-01-24 20:38:58, Zhang Yi wrote: >> From: Zhang Yi <yi.zhang@...wei.com> >> >> Add a new map flag EXT4_MAP_DELAYED to indicate the mapping range is a >> delayed allocated only (not unwritten) one, and making >> ext4_map_blocks() can distinguish it, no longer mixing it with holes. >> >> Signed-off-by: Zhang Yi <yi.zhang@...wei.com> > > One small comment below. > >> --- >> fs/ext4/ext4.h | 4 +++- >> fs/ext4/extents.c | 5 +++-- >> fs/ext4/inode.c | 2 ++ >> 3 files changed, 8 insertions(+), 3 deletions(-) >> >> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h >> index a5d784872303..55195909d32f 100644 >> --- a/fs/ext4/ext4.h >> +++ b/fs/ext4/ext4.h >> @@ -252,8 +252,10 @@ struct ext4_allocation_request { >> #define EXT4_MAP_MAPPED BIT(BH_Mapped) >> #define EXT4_MAP_UNWRITTEN BIT(BH_Unwritten) >> #define EXT4_MAP_BOUNDARY BIT(BH_Boundary) >> +#define EXT4_MAP_DELAYED BIT(BH_Delay) >> #define EXT4_MAP_FLAGS (EXT4_MAP_NEW | EXT4_MAP_MAPPED |\ >> - EXT4_MAP_UNWRITTEN | EXT4_MAP_BOUNDARY) >> + EXT4_MAP_UNWRITTEN | EXT4_MAP_BOUNDARY |\ >> + EXT4_MAP_DELAYED) >> >> struct ext4_map_blocks { >> ext4_fsblk_t m_pblk; >> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c >> index 0892d0568013..fc69f13cf510 100644 >> --- a/fs/ext4/extents.c >> +++ b/fs/ext4/extents.c >> @@ -4073,9 +4073,10 @@ static void ext4_ext_determine_hole(struct inode *inode, >> } else if (in_range(map->m_lblk, es.es_lblk, es.es_len)) { >> /* >> * Straddle the beginning of the queried range, it's no >> - * longer a hole, adjust the length to the delayed extent's >> - * after map->m_lblk. >> + * longer a hole, mark it is a delalloc and adjust the >> + * length to the delayed extent's after map->m_lblk. >> */ >> + map->m_flags |= EXT4_MAP_DELAYED; > > I wouldn't set delalloc bit here. If there's delalloc extent containing > lblk now, it means the caller of ext4_map_blocks() is not holding i_rwsem > (otherwise we would have found already in ext4_map_blocks()) and thus > delalloc info is unreliable anyway. So I wouldn't bother. But it's worth a > comment here like: > > /* > * There's delalloc extent containing lblk. It must have > * been added after ext4_map_blocks() checked the extent > * status tree so we are not holding i_rwsem and delalloc > * info is only stabilized by i_data_sem we are going to > * release soon. Don't modify the extent status tree and > * report extent as a hole. > */ > Yeah, the delalloc info is still unreliable. Thanks for the advice, I will revise it in my next iteration along with your advice in patch 03. Thanks, Yi. > >> len = es.es_lblk + es.es_len - map->m_lblk; >> goto out; >> } else { >> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c >> index 1b5e6409f958..c141bf6d8db2 100644 >> --- a/fs/ext4/inode.c >> +++ b/fs/ext4/inode.c >> @@ -515,6 +515,8 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, >> map->m_len = retval; >> } else if (ext4_es_is_delayed(&es) || ext4_es_is_hole(&es)) { >> map->m_pblk = 0; >> + map->m_flags |= ext4_es_is_delayed(&es) ? >> + EXT4_MAP_DELAYED : 0; >> retval = es.es_len - (map->m_lblk - es.es_lblk); >> if (retval > map->m_len) >> retval = map->m_len; >> -- >> 2.39.2 >>
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