On 9/17/25 13:52, Yunji Kang wrote:
> In f2fs_precache_extents(), For large files, It requires reading many
> node blocks. Instead of reading each node block with synchronous I/O,
> this patch applies readahead so that node blocks can be fetched in
> advance.
>
> It reduces the overhead of repeated sync reads and improves efficiency
> when precaching extents of large files.
>
> I created a file with the same largest extent and executed the test.
> For this experiment, I set the file's largest extent with an offset of 0
> and a size of 1GB. I configured the remaining area with 100MB extents.
>
> 5GB test file:
> dd if=/dev/urandom of=test1 bs=1m count=5120
> cp test1 test2
> fsync test1
> dd if=test1 of=test2 bs=1m skip=1024 seek=1024 count=100 conv=notrunc
> dd if=test1 of=test2 bs=1m skip=1224 seek=1224 count=100 conv=notrunc
> ...
> dd if=test1 of=test2 bs=1m skip=5024 seek=5024 count=100 conv=notrunc
> reboot
>
> I also created 10GB and 20GB files with large extents using the same
> method.
>
> ioctl(F2FS_IOC_PRECACHE_EXTENTS) test results are as follows:
> +-----------+---------+---------+-----------+
> | File size | Before | After | Reduction |
> +-----------+---------+---------+-----------+
> | 5GB | 101.8ms | 72.1ms | 29.2% |
> | 10GB | 222.9ms | 149.5ms | 32.9% |
> | 20GB | 446.2ms | 276.3ms | 38.1% |
> +-----------+---------+---------+-----------+
> Tested on a 256GB mobile device with an SM8750 chipset.
>
> Reviewed-by: Sungjong Seo <sj1557....@samsung.com>
> Reviewed-by: Sunmin Jeong <s_min.je...@samsung.com>
> Signed-off-by: Yunji Kang <yunji0.k...@samsung.com>
> ---
> fs/f2fs/data.c | 3 +++
> fs/f2fs/f2fs.h | 1 +
> fs/f2fs/node.c | 4 +++-
> 3 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 7961e0ddfca3..ab3117e3b24a 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1572,6 +1572,9 @@ int f2fs_map_blocks(struct inode *inode, struct
> f2fs_map_blocks *map, int flag)
> pgofs = (pgoff_t)map->m_lblk;
> end = pgofs + maxblocks;
>
> + if (flag == F2FS_GET_BLOCK_PRECACHE)
> + mode = LOOKUP_NODE_PRECACHE;
> +
> next_dnode:
> if (map->m_may_create) {
> if (f2fs_lfs_mode(sbi))
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 9d3bc9633c1d..3ce41528d48e 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -651,6 +651,7 @@ enum {
> * look up a node with readahead called
> * by get_data_block.
> */
> + LOOKUP_NODE_PRECACHE, /* look up a node for
> F2FS_GET_BLOCK_PRECACHE */
> };
>
> #define DEFAULT_RETRY_IO_COUNT 8 /* maximum retry read IO or
> flush count */
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 4254db453b2d..50be167e5c59 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -860,7 +860,9 @@ int f2fs_get_dnode_of_data(struct dnode_of_data *dn,
> pgoff_t index, int mode)
> set_nid(parent, offset[i - 1], nids[i], i == 1);
> f2fs_alloc_nid_done(sbi, nids[i]);
> done = true;
> - } else if (mode == LOOKUP_NODE_RA && i == level && level > 1) {
> + } else if ((mode == LOOKUP_NODE_RA ||
Does this change the logic for mode = LOOKUP_NODE_RA?
Not sure, do you mean this?
if ((i == level && level > 1) &&
(mode == LOOKUP_NODE_RA ||
(mode == LOOKUP_NODE_PRECACHE &&
offset[i - 1] % MAX_RA_NODE == 0)))
Thanks,
> + (mode == LOOKUP_NODE_PRECACHE && offset[i - 1]
> % MAX_RA_NODE == 0))
> + && i == level && level > 1) {
> nfolio[i] = f2fs_get_node_folio_ra(parent, offset[i -
> 1]);
> if (IS_ERR(nfolio[i])) {
> err = PTR_ERR(nfolio[i]);
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