[PATCH 0/2] erofs: support large folio in fscache mode

[PATCH 0/2] erofs: support large folio in fscache mode

[Jingbo Xu]

Patch 1 is the main part of supporting large folio in fscache mode. It
relies on a pending patch[1] adding .prepare_ondemand_read() interface
in Cachefiles.

Patch 2 just turns the switch on and enables the feature. It enables large
folio for both fscache and the original device mode (in uncompressed
data format). And thus I think the previous patch[2] exclusively for the
device mode is not needed then.

[1] https://lore.kernel.org/all/20221124034212.81892-1-jefflexu@linux.alibaba.com/
[2] https://lore.kernel.org/all/20221110074023.8059-1-jefflexu@linux.alibaba.com/


Jingbo Xu (2):
  erofs: support large folio in fscache mode
  erofs: enable large folio support for non-compressed format

 fs/erofs/fscache.c | 117 +++++++++++++++++++--------------------------
 fs/erofs/inode.c   |   1 +
 2 files changed, 50 insertions(+), 68 deletions(-)

-- 
2.19.1.6.gb485710b

[PATCH 1/2] erofs: support large folio in fscache mode

[Jingbo Xu]

When large folio supported, one folio can be split into several slices，
each of which may be mapped to META/UNMAPPED/MAPPED, and the folio can
be unlocked as a whole only when all slices have completed.

Thus always allocate erofs_fscache_request for each .read_folio() or
.readahead(). In this case, only when all slices of the folio or folio
range have completed, the request will be marked as completed and the
folio or folio range will be unlocked then.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
---
 fs/erofs/fscache.c | 116 +++++++++++++++++++--------------------------
 1 file changed, 48 insertions(+), 68 deletions(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 3cfe1af7a46e..0643b205c7eb 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -167,32 +167,18 @@ static int erofs_fscache_meta_read_folio(struct file *data, struct folio *folio)
 	return ret;
 }
 
-/*
- * Read into page cache in the range described by (@pos, @len).
- *
- * On return, if the output @unlock is true, the caller is responsible for page
- * unlocking; otherwise the callee will take this responsibility through request
- * completion.
- *
- * The return value is the number of bytes successfully handled, or negative
- * error code on failure. The only exception is that, the length of the range
- * instead of the error code is returned on failure after request is allocated,
- * so that .readahead() could advance rac accordingly.
- */
-static int erofs_fscache_data_read(struct address_space *mapping,
-				   loff_t pos, size_t len, bool *unlock)
+static int erofs_fscache_data_read_slice(struct erofs_fscache_request *req)
 {
+	struct address_space *mapping = req->mapping;
 	struct inode *inode = mapping->host;
 	struct super_block *sb = inode->i_sb;
-	struct erofs_fscache_request *req;
+	loff_t pos = req->start + req->submitted;
 	struct erofs_map_blocks map;
 	struct erofs_map_dev mdev;
 	struct iov_iter iter;
 	size_t count;
 	int ret;
 
-	*unlock = true;
-
 	map.m_la = pos;
 	ret = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
 	if (ret)
@@ -201,36 +187,37 @@ static int erofs_fscache_data_read(struct address_space *mapping,
 	if (map.m_flags & EROFS_MAP_META) {
 		struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
 		erofs_blk_t blknr;
-		size_t offset, size;
+		size_t offset;
 		void *src;
 
 		/* For tail packing layout, the offset may be non-zero. */
 		offset = erofs_blkoff(map.m_pa);
 		blknr = erofs_blknr(map.m_pa);
-		size = map.m_llen;
+		count = map.m_llen;
 
 		src = erofs_read_metabuf(&buf, sb, blknr, EROFS_KMAP);
 		if (IS_ERR(src))
 			return PTR_ERR(src);
 
-		iov_iter_xarray(&iter, READ, &mapping->i_pages, pos, PAGE_SIZE);
-		if (copy_to_iter(src + offset, size, &iter) != size) {
+		iov_iter_xarray(&iter, READ, &mapping->i_pages, pos, count);
+		if (copy_to_iter(src + offset, count, &iter) != count) {
 			erofs_put_metabuf(&buf);
 			return -EFAULT;
 		}
-		iov_iter_zero(PAGE_SIZE - size, &iter);
 		erofs_put_metabuf(&buf);
-		return PAGE_SIZE;
+		req->submitted += count;
+		return 0;
 	}
 
+	count = req->len - req->submitted;
 	if (!(map.m_flags & EROFS_MAP_MAPPED)) {
-		count = len;
 		iov_iter_xarray(&iter, READ, &mapping->i_pages, pos, count);
 		iov_iter_zero(count, &iter);
-		return count;
+		req->submitted += count;
+		return 0;
 	}
 
-	count = min_t(size_t, map.m_llen - (pos - map.m_la), len);
+	count = min_t(size_t, map.m_llen - (pos - map.m_la), count);
 	DBG_BUGON(!count || count % PAGE_SIZE);
 
 	mdev = (struct erofs_map_dev) {
@@ -241,68 +228,61 @@ static int erofs_fscache_data_read(struct address_space *mapping,
 	if (ret)
 		return ret;
 
-	req = erofs_fscache_req_alloc(mapping, pos, count);
-	if (IS_ERR(req))
-		return PTR_ERR(req);
-
-	*unlock = false;
-	ret = erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
+	return erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
 			req, mdev.m_pa + (pos - map.m_la), count);
-	if (ret)
-		req->error = ret;
+}
 
-	erofs_fscache_req_put(req);
-	return count;
+/*
+ * Read into page cache in the range described by (req->start, req->len).
+ */
+static int erofs_fscache_data_read(struct erofs_fscache_request *req)
+{
+	int ret;
+
+	do {
+		ret = erofs_fscache_data_read_slice(req);
+		if (ret)
+			req->error = ret;
+	} while (!ret && req->submitted < req->len);
+
+	return ret;
 }
 
 static int erofs_fscache_read_folio(struct file *file, struct folio *folio)
 {
-	bool unlock;
+	struct erofs_fscache_request *req;
 	int ret;
 
-	DBG_BUGON(folio_size(folio) != EROFS_BLKSIZ);
-
-	ret = erofs_fscache_data_read(folio_mapping(folio), folio_pos(folio),
-				      folio_size(folio), &unlock);
-	if (unlock) {
-		if (ret > 0)
-			folio_mark_uptodate(folio);
+	req = erofs_fscache_req_alloc(folio_mapping(folio),
+			folio_pos(folio), folio_size(folio));
+	if (IS_ERR(req)) {
 		folio_unlock(folio);
+		return PTR_ERR(req);
 	}
-	return ret < 0 ? ret : 0;
+
+	ret = erofs_fscache_data_read(req);
+	erofs_fscache_req_put(req);
+	return ret;
 }
 
 static void erofs_fscache_readahead(struct readahead_control *rac)
 {
-	struct folio *folio;
-	size_t len, done = 0;
-	loff_t start, pos;
-	bool unlock;
-	int ret, size;
+	struct erofs_fscache_request *req;
 
 	if (!readahead_count(rac))
 		return;
 
-	start = readahead_pos(rac);
-	len = readahead_length(rac);
+	req = erofs_fscache_req_alloc(rac->mapping,
+			readahead_pos(rac), readahead_length(rac));
+	if (IS_ERR(req))
+		return;
 
-	do {
-		pos = start + done;
-		ret = erofs_fscache_data_read(rac->mapping, pos,
-					      len - done, &unlock);
-		if (ret <= 0)
-			return;
+	/* The request completion will drop refs on the folios. */
+	while (readahead_folio(rac))
+		;
 
-		size = ret;
-		while (size) {
-			folio = readahead_folio(rac);
-			size -= folio_size(folio);
-			if (unlock) {
-				folio_mark_uptodate(folio);
-				folio_unlock(folio);
-			}
-		}
-	} while ((done += ret) < len);
+	erofs_fscache_data_read(req);
+	erofs_fscache_req_put(req);
 }
 
 static const struct address_space_operations erofs_fscache_meta_aops = {
-- 
2.19.1.6.gb485710b

[PATCH 2/2] erofs: enable large folio support for non-compressed format

[Jingbo Xu]

Enable large folio in both device and fscache mode.  Then the readahead
routine will pass down large folio containing multiple pages.

Enable this feature for non-compressed format for now, until the
compression part supports large folio later.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
---
 fs/erofs/fscache.c | 1 +
 fs/erofs/inode.c   | 1 +
 2 files changed, 2 insertions(+)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 0643b205c7eb..d2dd58ce312b 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -436,6 +436,7 @@ struct erofs_fscache *erofs_fscache_acquire_cookie(struct super_block *sb,
 		inode->i_size = OFFSET_MAX;
 		inode->i_mapping->a_ops = &erofs_fscache_meta_aops;
 		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
+		mapping_set_large_folios(inode->i_mapping);
 
 		ctx->inode = inode;
 	}
diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index ad2a82f2eb4c..85932086d23f 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -295,6 +295,7 @@ static int erofs_fill_inode(struct inode *inode)
 		goto out_unlock;
 	}
 	inode->i_mapping->a_ops = &erofs_raw_access_aops;
+	mapping_set_large_folios(inode->i_mapping);
 #ifdef CONFIG_EROFS_FS_ONDEMAND
 	if (erofs_is_fscache_mode(inode->i_sb))
 		inode->i_mapping->a_ops = &erofs_fscache_access_aops;
-- 
2.19.1.6.gb485710b

Re: [PATCH 2/2] erofs: enable large folio support for non-compressed format

[Gao Xiang]

Hi Jingbo,

On Sat, Nov 26, 2022 at 08:57:56AM +0800, Jingbo Xu wrote:
> Enable large folio in both device and fscache mode.  Then the readahead

         ^ large folios in both iomap and fscache modes.

I tend to enable iomap/fscache large folios with two patches.
Also please see dev-test branch.


> routine will pass down large folio containing multiple pages.
> 
> Enable this feature for non-compressed format for now, until the
> compression part supports large folio later.

                            ^ large folios

> 
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> ---
>  fs/erofs/fscache.c | 1 +
>  fs/erofs/inode.c   | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index 0643b205c7eb..d2dd58ce312b 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -436,6 +436,7 @@ struct erofs_fscache *erofs_fscache_acquire_cookie(struct super_block *sb,
>  		inode->i_size = OFFSET_MAX;
>  		inode->i_mapping->a_ops = &erofs_fscache_meta_aops;
>  		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
> +		mapping_set_large_folios(inode->i_mapping);
>  

Meta inodes currently doesn't need large folios for now, and
we don't have readahead policy for these.

>  		ctx->inode = inode;
>  	}
> diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
> index ad2a82f2eb4c..85932086d23f 100644
> --- a/fs/erofs/inode.c
> +++ b/fs/erofs/inode.c
> @@ -295,6 +295,7 @@ static int erofs_fill_inode(struct inode *inode)
>  		goto out_unlock;
>  	}
>  	inode->i_mapping->a_ops = &erofs_raw_access_aops;
> +	mapping_set_large_folios(inode->i_mapping);
>  #ifdef CONFIG_EROFS_FS_ONDEMAND
>  	if (erofs_is_fscache_mode(inode->i_sb))
>  		inode->i_mapping->a_ops = &erofs_fscache_access_aops;
> -- 
> 2.19.1.6.gb485710b
> 

Re: [PATCH 2/2] erofs: enable large folio support for non-compressed format

[Jingbo Xu]

On 11/26/22 10:16 AM, Gao Xiang wrote:
> Hi Jingbo,
> 
> On Sat, Nov 26, 2022 at 08:57:56AM +0800, Jingbo Xu wrote:
>> Enable large folio in both device and fscache mode.  Then the readahead
> 
>          ^ large folios in both iomap and fscache modes.
> 
> I tend to enable iomap/fscache large folios with two patches.
> Also please see dev-test branch.

Got it.


> 
> 
>> routine will pass down large folio containing multiple pages.
>>
>> Enable this feature for non-compressed format for now, until the
>> compression part supports large folio later.
> 
>                             ^ large folios
> 
>>
>> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
>> ---
>>  fs/erofs/fscache.c | 1 +
>>  fs/erofs/inode.c   | 1 +
>>  2 files changed, 2 insertions(+)
>>
>> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
>> index 0643b205c7eb..d2dd58ce312b 100644
>> --- a/fs/erofs/fscache.c
>> +++ b/fs/erofs/fscache.c
>> @@ -436,6 +436,7 @@ struct erofs_fscache *erofs_fscache_acquire_cookie(struct super_block *sb,
>>  		inode->i_size = OFFSET_MAX;
>>  		inode->i_mapping->a_ops = &erofs_fscache_meta_aops;
>>  		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
>> +		mapping_set_large_folios(inode->i_mapping);
>>  
> 
> Meta inodes currently doesn't need large folios for now, and
> we don't have readahead policy for these.

Alright, I will fix this in a quick v2.

> 
>>  		ctx->inode = inode;
>>  	}
>> diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
>> index ad2a82f2eb4c..85932086d23f 100644
>> --- a/fs/erofs/inode.c
>> +++ b/fs/erofs/inode.c
>> @@ -295,6 +295,7 @@ static int erofs_fill_inode(struct inode *inode)
>>  		goto out_unlock;
>>  	}
>>  	inode->i_mapping->a_ops = &erofs_raw_access_aops;
>> +	mapping_set_large_folios(inode->i_mapping);
>>  #ifdef CONFIG_EROFS_FS_ONDEMAND
>>  	if (erofs_is_fscache_mode(inode->i_sb))
>>  		inode->i_mapping->a_ops = &erofs_fscache_access_aops;
>> -- 
>> 2.19.1.6.gb485710b
>>

-- 
Thanks,
Jingbo