Messages in this thread | | | Date | Mon, 9 Oct 2023 10:56:41 -0700 | From | Jaegeuk Kim <> | Subject | Re: [f2fs-dev] [PATCH] f2fs: stop iterating f2fs_map_block if hole exists |
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On 10/07, Chao Yu wrote: > On 2023/10/4 6:52, Jaegeuk Kim wrote: > > Let's avoid unnecessary f2fs_map_block calls to load extents. > > > > # f2fs_io fadvise willneed 0 4096 /data/local/tmp/test > > > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 386, start blkaddr = 0x34ac00, len = 0x1400, flags = 2, > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 5506, start blkaddr = 0x34c200, len = 0x1000, flags = 2, > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 9602, start blkaddr = 0x34d600, len = 0x1200, flags = 2, > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 14210, start blkaddr = 0x34ec00, len = 0x400, flags = 2, > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 15235, start blkaddr = 0x34f401, len = 0xbff, flags = 2, > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 18306, start blkaddr = 0x350200, len = 0x1200, flags = 2 > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 22915, start blkaddr = 0x351601, len = 0xa7d, flags = 2 > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 25600, start blkaddr = 0x351601, len = 0x0, flags = 0 > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 25601, start blkaddr = 0x351601, len = 0x0, flags = 0 > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 25602, start blkaddr = 0x351601, len = 0x0, flags = 0 > > ... > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 1037188, start blkaddr = 0x351601, len = 0x0, flags = 0 > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 1038206, start blkaddr = 0x351601, len = 0x0, flags = 0 > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 1039224, start blkaddr = 0x351601, len = 0x0, flags = 0 > > f2fs_map_blocks: dev = (254,51), ino = 85845, file offset = 2075548, start blkaddr = 0x351601, len = 0x0, flags = 0 > > Jaegeuk, > > Not sure, but it looks it's due to f2fs_precache_extents() will traverse file > w/ range [0, max_file_blocks), since data which exceeds EOF will always be zero, > so it's not necessary to precache its mapping info, so we'd better adjust upper > boundary to i_size rather than max_file_blocks(). > > > > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > > --- > > fs/f2fs/file.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > > index 161826c6e200..2403fd1de5a0 100644 > > --- a/fs/f2fs/file.c > > +++ b/fs/f2fs/file.c > > @@ -3270,7 +3270,7 @@ int f2fs_precache_extents(struct inode *inode) > > f2fs_down_write(&fi->i_gc_rwsem[WRITE]); > > err = f2fs_map_blocks(inode, &map, F2FS_GET_BLOCK_PRECACHE); > > f2fs_up_write(&fi->i_gc_rwsem[WRITE]); > > - if (err) > > + if (err || !map.m_len) > Well, if there is a hole in the head of file, it may break here rather > than precaching following valid map info. > > What about passing parameter offset|len from f2fs_file_fadvise() to > f2fs_precache_extents(), and then precaching mapping info on demand.
I'd rather stop reading metadata if it meets a hole within i_size, since this gives benefits when reading the entire non-hole case, FWIW. Rather than that, I think generic readahead flow can hide the metadata loading.
> > Thanks, > > > return err; > > map.m_lblk = m_next_extent;
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