linux.git/fs/erofs/data.c, branch v6.13

erofs: reference `struct erofs_device_info` for erofs_map_dev

2024-12-16T13:02:06+00:00

Record `m_sb` and `m_dif` to replace `m_fscache`, `m_daxdev`, `m_fp`
and `m_dax_part_off` in order to simplify the codebase.

Note that `m_bdev` is still left since it can be assigned from
`sb->s_bdev` directly.

Reviewed-by: Chao Yu 
Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20241212235401.2857246-1-hsiangkao@linux.alibaba.com

erofs: use `struct erofs_device_info` for the primary device

2024-12-16T13:01:59+00:00

Instead of just listing each one directly in `struct erofs_sb_info`
except that we still use `sb->s_bdev` for the primary block device.

Reviewed-by: Chao Yu 
Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20241216125310.930933-2-hsiangkao@linux.alibaba.com

erofs: clarify direct I/O support

2024-11-18T10:50:14+00:00

Currently, only filesystems backed by block devices support direct I/O.

Also remove the unnecessary strict checks that can be supported with iomap.

Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20241115074625.2520728-1-hsiangkao@linux.alibaba.com

erofs: get rid of `buf->kmap_type`

2024-11-18T10:50:14+00:00

After commit 927e5010ff5b ("erofs: use kmap_local_page() only for
erofs_bread()"), `buf->kmap_type` actually has no use at all.

Let's get rid of `buf->kmap_type` now.

Suggested-by: Al Viro 
Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20241114095813.839866-1-hsiangkao@linux.alibaba.com

erofs: fix file-backed mounts over FUSE

2024-11-18T10:50:13+00:00

syzbot reported a null-ptr-deref in fuse_read_args_fill:
 fuse_read_folio+0xb0/0x100 fs/fuse/file.c:905
 filemap_read_folio+0xc6/0x2a0 mm/filemap.c:2367
 do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3825
 read_mapping_folio include/linux/pagemap.h:1011 [inline]
 erofs_bread+0x34d/0x7e0 fs/erofs/data.c:41
 erofs_read_superblock fs/erofs/super.c:281 [inline]
 erofs_fc_fill_super+0x2b9/0x2500 fs/erofs/super.c:625

Unlike most filesystems, some network filesystems and FUSE need
unavoidable valid `file` pointers for their read I/Os [1].
Anyway, those use cases need to be supported too.

[1] https://docs.kernel.org/filesystems/vfs.html

Reported-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/6727bbdf.050a0220.3c8d68.0a7e.GAE@google.com
Fixes: fb176750266a ("erofs: add file-backed mount support")
Tested-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com
Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20241114234905.1873723-1-hsiangkao@linux.alibaba.com

erofs: add SEEK_{DATA,HOLE} support

2024-11-12T02:25:19+00:00

Many userspace programs (including erofs-utils itself) use SEEK_DATA /
SEEK_HOLE to parse hole extents in addition to FIEMAP.

Reviewed-by: Chao Yu 
Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20241011065128.2097377-1-hsiangkao@linux.alibaba.com

erofs: simplify erofs_map_blocks_flatmode()

2024-09-10T07:27:14+00:00

Get rid of redundant variables (nblocks, offset) and a dead branch
(!tailendpacking).

Signed-off-by: Hongzhen Luo 
Reviewed-by: Gao Xiang 
Reviewed-by: Chao Yu 
Link: https://lore.kernel.org/r/20240905030339.1474396-1-hongzhen@linux.alibaba.com
Signed-off-by: Gao Xiang

erofs: support unencoded inodes for fileio

2024-09-10T07:26:36+00:00

Since EROFS only needs to handle read requests in simple contexts,
Just directly use vfs_iocb_iter_read() for data I/Os.

Reviewed-by: Sandeep Dhavale 
Reviewed-by: Chao Yu 
Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20240905093031.2745929-1-hsiangkao@linux.alibaba.com

erofs: add file-backed mount support

2024-09-10T07:26:35+00:00

It actually has been around for years: For containers and other sandbox
use cases, there will be thousands (and even more) of authenticated
(sub)images running on the same host, unlike OS images.

Of course, all scenarios can use the same EROFS on-disk format, but
bdev-backed mounts just work well for OS images since golden data is
dumped into real block devices.  However, it's somewhat hard for
container runtimes to manage and isolate so many unnecessary virtual
block devices safely and efficiently [1]: they just look like a burden
to orchestrators and file-backed mounts are preferred indeed.  There
were already enough attempts such as Incremental FS, the original
ComposeFS and PuzzleFS acting in the same way for immutable fses.  As
for current EROFS users, ComposeFS, containerd and Android APEXs will
be directly benefited from it.

On the other hand, previous experimental feature "erofs over fscache"
was once also intended to provide a similar solution (inspired by
Incremental FS discussion [2]), but the following facts show file-backed
mounts will be a better approach:
 - Fscache infrastructure has recently been moved into new Netfslib
   which is an unexpected dependency to EROFS really, although it
   originally claims "it could be used for caching other things such as
   ISO9660 filesystems too." [3]

 - It takes an unexpectedly long time to upstream Fscache/Cachefiles
   enhancements.  For example, the failover feature took more than
   one year, and the deamonless feature is still far behind now;

 - Ongoing HSM "fanotify pre-content hooks" [4] together with this will
   perfectly supersede "erofs over fscache" in a simpler way since
   developers (mainly containerd folks) could leverage their existing
   caching mechanism entirely in userspace instead of strictly following
   the predefined in-kernel caching tree hierarchy.

After "fanotify pre-content hooks" lands upstream to provide the same
functionality, "erofs over fscache" will be removed then (as an EROFS
internal improvement and EROFS will not have to bother with on-demand
fetching and/or caching improvements anymore.)

[1] https://github.com/containers/storage/pull/2039
[2] https://lore.kernel.org/r/CAOQ4uxjbVxnubaPjVaGYiSwoGDTdpWbB=w_AeM6YM=zVixsUfQ@mail.gmail.com
[3] https://docs.kernel.org/filesystems/caching/fscache.html
[4] https://lore.kernel.org/r/cover.1723670362.git.josef@toxicpanda.com

Closes: https://github.com/containers/composefs/issues/144
Reviewed-by: Sandeep Dhavale 
Reviewed-by: Chao Yu 
Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20240830032840.3783206-1-hsiangkao@linux.alibaba.com

erofs: support multi-page folios for erofs_bread()

2024-07-26T10:47:57+00:00

If the requested page is part of the previous multi-page folio, there
is no need to call read_mapping_folio() again.

Also, get rid of the remaining one of page->index [1] in our codebase.

[1] https://lore.kernel.org/r/Zp8fgUSIBGQ1TN0D@casper.infradead.org

Cc: Matthew Wilcox 
Reviewed-by: Chao Yu 
Signed-off-by: Gao Xiang 
Link: https://lore.kernel.org/r/20240723073024.875290-1-hsiangkao@linux.alibaba.com