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Date: Wed, 2 Jun 2021 00:16:08 +0100 (BST)
From: Phillip Lougher <phillip@...ashfs.org.uk>
To: Vincent Whitchurch <vincent.whitchurch@...s.com>,
akpm@...ux-foundation.org
Cc: kernel@...s.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] squashfs: add option to panic on errors
> On 27/05/2021 13:50 Vincent Whitchurch <vincent.whitchurch@...s.com> wrote:
>
>
> Add an errors=panic mount option to make squashfs trigger a panic when
> errors are encountered, similar to several other filesystems. This
> allows a kernel dump to be saved using which the corruption can be
> analysed and debugged.
>
> Inspired by a pre-fs_context patch by Anton Eliasson.
This looks like a worthwhile improvement.
Signed-off-by: Phillip Lougher <phillip@...ashfs.org.uk>
Thanks
Phillip
--
Squashfs maintainer.
>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> ---
> fs/squashfs/block.c | 5 ++-
> fs/squashfs/squashfs_fs_sb.h | 1 +
> fs/squashfs/super.c | 86 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 91 insertions(+), 1 deletion(-)
>
> diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
> index b9e87ebb1060..855f0e87066d 100644
> --- a/fs/squashfs/block.c
> +++ b/fs/squashfs/block.c
> @@ -226,8 +226,11 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
> bio_free_pages(bio);
> bio_put(bio);
> out:
> - if (res < 0)
> + if (res < 0) {
> ERROR("Failed to read block 0x%llx: %d\n", index, res);
> + if (msblk->panic_on_errors)
> + panic("squashfs read failed");
> + }
>
> return res;
> }
> diff --git a/fs/squashfs/squashfs_fs_sb.h b/fs/squashfs/squashfs_fs_sb.h
> index 166e98806265..1e90c2575f9b 100644
> --- a/fs/squashfs/squashfs_fs_sb.h
> +++ b/fs/squashfs/squashfs_fs_sb.h
> @@ -65,5 +65,6 @@ struct squashfs_sb_info {
> unsigned int fragments;
> int xattr_ids;
> unsigned int ids;
> + bool panic_on_errors;
> };
> #endif
> diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
> index 88cc94be1076..60d6951915f4 100644
> --- a/fs/squashfs/super.c
> +++ b/fs/squashfs/super.c
> @@ -18,9 +18,11 @@
>
> #include <linux/fs.h>
> #include <linux/fs_context.h>
> +#include <linux/fs_parser.h>
> #include <linux/vfs.h>
> #include <linux/slab.h>
> #include <linux/mutex.h>
> +#include <linux/seq_file.h>
> #include <linux/pagemap.h>
> #include <linux/init.h>
> #include <linux/module.h>
> @@ -37,6 +39,51 @@
> static struct file_system_type squashfs_fs_type;
> static const struct super_operations squashfs_super_ops;
>
> +enum Opt_errors {
> + Opt_errors_continue,
> + Opt_errors_panic,
> +};
> +
> +enum squashfs_param {
> + Opt_errors,
> +};
> +
> +struct squashfs_mount_opts {
> + enum Opt_errors errors;
> +};
> +
> +static const struct constant_table squashfs_param_errors[] = {
> + {"continue", Opt_errors_continue },
> + {"panic", Opt_errors_panic },
> + {}
> +};
> +
> +static const struct fs_parameter_spec squashfs_fs_parameters[] = {
> + fsparam_enum("errors", Opt_errors, squashfs_param_errors),
> + {}
> +};
> +
> +static int squashfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
> +{
> + struct squashfs_mount_opts *opts = fc->fs_private;
> + struct fs_parse_result result;
> + int opt;
> +
> + opt = fs_parse(fc, squashfs_fs_parameters, param, &result);
> + if (opt < 0)
> + return opt;
> +
> + switch (opt) {
> + case Opt_errors:
> + opts->errors = result.uint_32;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> static const struct squashfs_decompressor *supported_squashfs_filesystem(
> struct fs_context *fc,
> short major, short minor, short id)
> @@ -67,6 +114,7 @@ static const struct squashfs_decompressor *supported_squashfs_filesystem(
>
> static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
> {
> + struct squashfs_mount_opts *opts = fc->fs_private;
> struct squashfs_sb_info *msblk;
> struct squashfs_super_block *sblk = NULL;
> struct inode *root;
> @@ -85,6 +133,8 @@ static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
> }
> msblk = sb->s_fs_info;
>
> + msblk->panic_on_errors = (opts->errors == Opt_errors_panic);
> +
> msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
> msblk->devblksize_log2 = ffz(~msblk->devblksize);
>
> @@ -350,18 +400,52 @@ static int squashfs_get_tree(struct fs_context *fc)
>
> static int squashfs_reconfigure(struct fs_context *fc)
> {
> + struct super_block *sb = fc->root->d_sb;
> + struct squashfs_sb_info *msblk = sb->s_fs_info;
> + struct squashfs_mount_opts *opts = fc->fs_private;
> +
> sync_filesystem(fc->root->d_sb);
> fc->sb_flags |= SB_RDONLY;
> +
> + msblk->panic_on_errors = (opts->errors == Opt_errors_panic);
> +
> return 0;
> }
>
> +static void squashfs_free_fs_context(struct fs_context *fc)
> +{
> + kfree(fc->fs_private);
> +}
> +
> static const struct fs_context_operations squashfs_context_ops = {
> .get_tree = squashfs_get_tree,
> + .free = squashfs_free_fs_context,
> + .parse_param = squashfs_parse_param,
> .reconfigure = squashfs_reconfigure,
> };
>
> +static int squashfs_show_options(struct seq_file *s, struct dentry *root)
> +{
> + struct super_block *sb = root->d_sb;
> + struct squashfs_sb_info *msblk = sb->s_fs_info;
> +
> + if (msblk->panic_on_errors)
> + seq_puts(s, ",errors=panic");
> + else
> + seq_puts(s, ",errors=continue");
> +
> + return 0;
> +}
> +
> static int squashfs_init_fs_context(struct fs_context *fc)
> {
> + struct squashfs_mount_opts *opts;
> +
> + opts = kzalloc(sizeof(*opts), GFP_KERNEL);
> + if (!opts)
> + return -ENOMEM;
> +
> + fc->fs_private = opts;
> fc->ops = &squashfs_context_ops;
> return 0;
> }
> @@ -481,6 +565,7 @@ static struct file_system_type squashfs_fs_type = {
> .owner = THIS_MODULE,
> .name = "squashfs",
> .init_fs_context = squashfs_init_fs_context,
> + .parameters = squashfs_fs_parameters,
> .kill_sb = kill_block_super,
> .fs_flags = FS_REQUIRES_DEV
> };
> @@ -491,6 +576,7 @@ static const struct super_operations squashfs_super_ops = {
> .free_inode = squashfs_free_inode,
> .statfs = squashfs_statfs,
> .put_super = squashfs_put_super,
> + .show_options = squashfs_show_options,
> };
>
> module_init(init_squashfs_fs);
> --
> 2.28.0
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