Commit 6422cde1 authored by Gao Xiang's avatar Gao Xiang
Browse files

erofs: use buffered I/O for file-backed mounts by default 



For many use cases (e.g. container images are just fetched from remote),
performance will be impacted if underlay page cache is up-to-date but
direct i/o flushes dirty pages first.

Instead, let's use buffered I/O by default to keep in sync with loop
devices and add a (re)mount option to explicitly give a try to use
direct I/O if supported by the underlying files.

The container startup time is improved as below:
[workload] docker.io/library/workpress:latest
                                     unpack        1st run  non-1st runs
EROFS snapshotter buffered I/O file  4.586404265s  0.308s   0.198s
EROFS snapshotter direct I/O file    4.581742849s  2.238s   0.222s
EROFS snapshotter loop               4.596023152s  0.346s   0.201s
Overlayfs snapshotter                5.382851037s  0.206s   0.214s

Fixes: fb176750 ("erofs: add file-backed mount support")
Cc: Derek McGowan <derek@mcg.dev>
Reviewed-by: default avatarChao Yu <chao@kernel.org>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241212134336.2059899-1-hsiangkao@linux.alibaba.com
parent f8d920a4

fs/erofs/fileio.c

+5 −2
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ struct erofs_fileio_rq { 
	struct bio_vec bvecs[BIO_MAX_VECS];

	struct bio bio;

	struct kiocb iocb;

	struct super_block *sb;

};



struct erofs_fileio {
@@ -52,8 +53,9 @@ static void erofs_fileio_rq_submit(struct erofs_fileio_rq *rq) 
	rq->iocb.ki_pos = rq->bio.bi_iter.bi_sector << SECTOR_SHIFT;

	rq->iocb.ki_ioprio = get_current_ioprio();

	rq->iocb.ki_complete = erofs_fileio_ki_complete;

	rq->iocb.ki_flags = (rq->iocb.ki_filp->f_mode & FMODE_CAN_ODIRECT) ?

				IOCB_DIRECT : 0;

	if (test_opt(&EROFS_SB(rq->sb)->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,

		      rq->bio.bi_iter.bi_size);

	ret = vfs_iocb_iter_read(rq->iocb.ki_filp, &rq->iocb, &iter);
@@ -68,6 +70,7 @@ static struct erofs_fileio_rq *erofs_fileio_rq_alloc(struct erofs_map_dev *mdev) 


	bio_init(&rq->bio, NULL, rq->bvecs, BIO_MAX_VECS, REQ_OP_READ);

	rq->iocb.ki_filp = mdev->m_dif->file;

	rq->sb = mdev->m_sb;

	return rq;

}

fs/erofs/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -176,6 +176,7 @@ struct erofs_sb_info { 
#define EROFS_MOUNT_POSIX_ACL		0x00000020

#define EROFS_MOUNT_DAX_ALWAYS		0x00000040

#define EROFS_MOUNT_DAX_NEVER		0x00000080

#define EROFS_MOUNT_DIRECT_IO		0x00000100



#define clear_opt(opt, option)	((opt)->mount_opt &= ~EROFS_MOUNT_##option)

#define set_opt(opt, option)	((opt)->mount_opt |= EROFS_MOUNT_##option)

fs/erofs/super.c

+15 −8
Original line number Diff line number Diff line
@@ -364,14 +364,8 @@ 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_user_xattr, Opt_acl, Opt_cache_strategy, Opt_dax, Opt_dax_enum,

	Opt_device, Opt_fsid, Opt_domain_id, Opt_directio,

	Opt_err

};
@@ -398,6 +392,7 @@ static const struct fs_parameter_spec erofs_fs_parameters[] = { 
	fsparam_string("device",	Opt_device),

	fsparam_string("fsid",		Opt_fsid),

	fsparam_string("domain_id",	Opt_domain_id),

	fsparam_flag_no("directio",	Opt_directio),

	{}

};
@@ -511,6 +506,16 @@ static int erofs_fc_parse_param(struct fs_context *fc, 
		errorfc(fc, "%s option not supported", erofs_fs_parameters[opt].name);

		break;

#endif

	case Opt_directio:

#ifdef CONFIG_EROFS_FS_BACKED_BY_FILE

		if (result.boolean)

			set_opt(&sbi->opt, DIRECT_IO);

		else

			clear_opt(&sbi->opt, DIRECT_IO);

#else

		errorfc(fc, "%s option not supported", erofs_fs_parameters[opt].name);

#endif

		break;

	default:

		return -ENOPARAM;

	}
@@ -948,6 +953,8 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root) 
		seq_puts(seq, ",dax=always");

	if (test_opt(opt, DAX_NEVER))

		seq_puts(seq, ",dax=never");

	if (erofs_is_fileio_mode(sbi) && test_opt(opt, DIRECT_IO))

		seq_puts(seq, ",directio");

#ifdef CONFIG_EROFS_FS_ONDEMAND

	if (sbi->fsid)

		seq_printf(seq, ",fsid=%s", sbi->fsid);