From: Sheng Yong <shengyo...@xiaomi.com>
When attempting to use an archive file, such as APEX on android,
as a file-backed mount source, it fails because EROFS image within
the archive file does not start at offset 0. As a result, a loop
device is still needed to attach the image file at an appropriate
offset first.
To address this issue, this patch parses the `source' parameter in
EROFS to accept a start offset for the file-backed mount. The format
is `/path/to/archive_file:offs', where `offs' represents the start
offset. EROFS will add this offset before performing read requests.
Signed-off-by: Sheng Yong <shengyo...@xiaomi.com>
Signed-off-by: Wang Shuai <wangshua...@xiaomi.com>
---
fs/erofs/data.c | 7 ++++++-
fs/erofs/fileio.c | 8 ++++++--
fs/erofs/internal.h | 2 ++
fs/erofs/super.c | 37 ++++++++++++++++++++++++++++++++++++-
4 files changed, 50 insertions(+), 4 deletions(-)
diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index 2409d2ab0c28..957743201ef5 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -27,9 +27,12 @@ void erofs_put_metabuf(struct erofs_buf *buf)
void *erofs_bread(struct erofs_buf *buf, erofs_off_t offset, bool need_kmap)
{
- pgoff_t index = offset >> PAGE_SHIFT;
+ pgoff_t index;
struct folio *folio = NULL;
+ offset += buf->fofs;
+ index = offset >> PAGE_SHIFT;
+
if (buf->page) {
folio = page_folio(buf->page);
if (folio_file_page(folio, index) != buf->page)
@@ -54,9 +57,11 @@ void erofs_init_metabuf(struct erofs_buf *buf, struct
super_block *sb)
struct erofs_sb_info *sbi = EROFS_SB(sb);
buf->file = NULL;
+ buf->fofs = 0;
if (erofs_is_fileio_mode(sbi)) {
buf->file = sbi->dif0.file; /* some fs like FUSE needs it */
buf->mapping = buf->file->f_mapping;
+ buf->fofs = sbi->dif0.fofs;
} else if (erofs_is_fscache_mode(sb))
buf->mapping = sbi->dif0.fscache->inode->i_mapping;
else
diff --git a/fs/erofs/fileio.c b/fs/erofs/fileio.c
index bec4b56b3826..62288ef19920 100644
--- a/fs/erofs/fileio.c
+++ b/fs/erofs/fileio.c
@@ -45,15 +45,19 @@ static void erofs_fileio_ki_complete(struct kiocb *iocb,
long ret)
static void erofs_fileio_rq_submit(struct erofs_fileio_rq *rq)
{
+ struct erofs_sb_info *sbi;
struct iov_iter iter;
int ret;
if (!rq)
return;
- rq->iocb.ki_pos = rq->bio.bi_iter.bi_sector << SECTOR_SHIFT;
+
+ sbi = EROFS_SB(rq->sb);
+ rq->iocb.ki_pos = sbi->dif0.fofs +
+ (rq->bio.bi_iter.bi_sector << SECTOR_SHIFT);
rq->iocb.ki_ioprio = get_current_ioprio();
rq->iocb.ki_complete = erofs_fileio_ki_complete;
- if (test_opt(&EROFS_SB(rq->sb)->opt, DIRECT_IO) &&
+ if (test_opt(&sbi->opt, DIRECT_IO) &&
rq->iocb.ki_filp->f_mode & FMODE_CAN_ODIRECT)
rq->iocb.ki_flags = IOCB_DIRECT;
iov_iter_bvec(&iter, ITER_DEST, rq->bvecs, rq->bio.bi_vcnt,
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 4ac188d5d894..b0a752b955f6 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -43,6 +43,7 @@ struct erofs_device_info {
char *path;
struct erofs_fscache *fscache;
struct file *file;
+ loff_t fofs;
struct dax_device *dax_dev;
u64 dax_part_off;
@@ -199,6 +200,7 @@ enum {
struct erofs_buf {
struct address_space *mapping;
struct file *file;
+ loff_t fofs;
struct page *page;
void *base;
};
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index cadec6b1b554..87ddeb327a8a 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -356,7 +356,7 @@ static void erofs_default_options(struct erofs_sb_info *sbi)
enum {
Opt_user_xattr, Opt_acl, Opt_cache_strategy, Opt_dax, Opt_dax_enum,
- Opt_device, Opt_fsid, Opt_domain_id, Opt_directio,
+ Opt_device, Opt_fsid, Opt_domain_id, Opt_directio, Opt_source,
Opt_err
};
@@ -384,6 +384,7 @@ static const struct fs_parameter_spec erofs_fs_parameters[]
= {
fsparam_string("fsid", Opt_fsid),
fsparam_string("domain_id", Opt_domain_id),
fsparam_flag_no("directio", Opt_directio),
+ fsparam_string("source", Opt_source),
{}
};
@@ -411,6 +412,31 @@ static bool erofs_fc_set_dax_mode(struct fs_context *fc,
unsigned int mode)
#endif
}
+static loff_t erofs_fc_parse_source(struct fs_context *fc,
+ struct fs_parameter *param)
+{
+ const char *devname = param->string;
+ const char *fofs_start __maybe_unused;
+ loff_t fofs = 0;
+
+ if (!devname || !*devname)
+ return invalfc(fc, "Empty source");
+
+#ifdef CONFIG_EROFS_FS_BACKED_BY_FILE
+ fofs_start = strchr(devname, ':');
+ if (!fofs_start)
+ goto out;
+ if (kstrtoll(fofs_start + 1, 0, &fofs) < 0)
+ return invalfc(fc, "Invalid filebacked offset %s", fofs_start);
+ fc->source = kstrndup(devname, fofs_start - devname, GFP_KERNEL);
+ return fofs;
+out:
+#endif
+ fc->source = devname;
+ param->string = NULL;
+ return fofs;
+}
+
static int erofs_fc_parse_param(struct fs_context *fc,
struct fs_parameter *param)
{
@@ -507,6 +533,11 @@ static int erofs_fc_parse_param(struct fs_context *fc,
errorfc(fc, "%s option not supported",
erofs_fs_parameters[opt].name);
#endif
break;
+ case Opt_source:
+ sbi->dif0.fofs = erofs_fc_parse_source(fc, param);
+ if (sbi->dif0.fofs < 0)
+ return -EINVAL;
+ break;
}
return 0;
}
@@ -697,6 +728,10 @@ static int erofs_fc_get_tree(struct fs_context *fc)
file = filp_open(fc->source, O_RDONLY | O_LARGEFILE, 0);
if (IS_ERR(file))
return PTR_ERR(file);
+ if (sbi->dif0.fofs + PAGE_SIZE >=
i_size_read(file_inode(file))) {
+ fput(file);
+ return invalf(fc, "Start offset too large");
+ }
sbi->dif0.file = file;
if (S_ISREG(file_inode(sbi->dif0.file)->i_mode) &&
--
2.43.0
