Messages in this thread | | | Date | Thu, 18 Apr 2024 15:49:22 +0800 | From | Gao Xiang <> | Subject | Re: [PATCH v2] erofs: reliably distinguish block based and fscache mode |
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Hi,
On Thu, Apr 18, 2024 at 02:12:39PM +0800, Baokun Li wrote: > On 2024/4/18 13:50, Jingbo Xu wrote: > > > > On 4/18/24 11:36 AM, Baokun Li wrote: > > > On 2024/4/18 10:16, Jingbo Xu wrote: > > > > Hi Baokun, > > > > > > > > Thanks for catching this and move forward fixing this! > > > Hi Jingbo, > > > > > > Thanks for your review! > > > > > > > On 4/17/24 2:55 PM, Baokun Li wrote: > > > > > When erofs_kill_sb() is called in block dev based mode, s_bdev may > > > > > not have > > > > > been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it > > > > > will > > > > > be mistaken for fscache mode, and then attempt to free an anon_dev > > > > > that has > > > > > never been allocated, triggering the following warning: > > > > > > > > > > ============================================ > > > > > ida_free called for id=0 which is not allocated. > > > > > WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140 > > > > > Modules linked in: > > > > > CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630 > > > > > RIP: 0010:ida_free+0x134/0x140 > > > > > Call Trace: > > > > > <TASK> > > > > > erofs_kill_sb+0x81/0x90 > > > > > deactivate_locked_super+0x35/0x80 > > > > > get_tree_bdev+0x136/0x1e0 > > > > > vfs_get_tree+0x2c/0xf0 > > > > > do_new_mount+0x190/0x2f0 > > > > > [...] > > > > > ============================================ > > > > > > > > > > Instead of allocating the erofs_sb_info in fill_super() allocate it > > > > > during erofs_get_tree() and ensure that erofs can always have the info > > > > > available during erofs_kill_sb(). > > > > I'm not sure if allocating erofs_sb_info in erofs_init_fs_context() will > > > > be better, as I see some filesystems (e.g. autofs) do this way. Maybe > > > > another potential advantage of doing this way is that erofs_fs_context > > > > is not needed anymore and we can use sbi directly. > > > Yes, except for some extra memory usage when remounting, > > > this idea sounds great. Let me send a version of v3 to get rid > > > of erofs_fs_context. > > I'm not sure if Gao Xaing also prefers this. I think it would be better > > to wait and listen for his thoughts before we sending v3. > Okay, there's no rush on this.
I checked days ago, for example, XFS is also worked in this way. And .reconfigure() needs to be carefully handled too.
> > > > > Signed-off-by: Christian Brauner <brauner@kernel.org> > > > > > Signed-off-by: Baokun Li <libaokun1@huawei.com> > > > > > --- > > > > > Changes since v1: > > > > > Allocate and initialise fc->s_fs_info in erofs_fc_get_tree() > > > > > instead of > > > > > modifying fc->sb_flags. > > > > > > > > > > V1: > > > > > https://lore.kernel.org/r/20240415121746.1207242-1-libaokun1@huawei.com/ > > > > > > > > > > fs/erofs/super.c | 51 ++++++++++++++++++++++++++---------------------- > > > > > 1 file changed, 28 insertions(+), 23 deletions(-) > > > > > > > > > > diff --git a/fs/erofs/super.c b/fs/erofs/super.c > > > > > index b21bd8f78dc1..4104280be2ea 100644 > > > > > --- a/fs/erofs/super.c > > > > > +++ b/fs/erofs/super.c > > > > > @@ -581,8 +581,7 @@ static const struct export_operations > > > > > erofs_export_ops = { > > > > > static int erofs_fc_fill_super(struct super_block *sb, struct > > > > > fs_context *fc) > > > > > { > > > > > struct inode *inode; > > > > > - struct erofs_sb_info *sbi; > > > > > - struct erofs_fs_context *ctx = fc->fs_private; > > > > > + struct erofs_sb_info *sbi = EROFS_SB(sb); > > > > > int err; > > > > > sb->s_magic = EROFS_SUPER_MAGIC; > > > > > @@ -590,19 +589,6 @@ static int erofs_fc_fill_super(struct > > > > > super_block *sb, struct fs_context *fc) > > > > > sb->s_maxbytes = MAX_LFS_FILESIZE; > > > > > sb->s_op = &erofs_sops; > > > > > - sbi = kzalloc(sizeof(*sbi), GFP_KERNEL); > > > > > - if (!sbi) > > > > > - return -ENOMEM; > > > > > - > > > > > - sb->s_fs_info = sbi; > > > > > - sbi->opt = ctx->opt; > > > > > - sbi->devs = ctx->devs; > > > > > - ctx->devs = NULL; > > > > > - sbi->fsid = ctx->fsid; > > > > > - ctx->fsid = NULL; > > > > > - sbi->domain_id = ctx->domain_id; > > > > > - ctx->domain_id = NULL; > > > > > - > > > > > sbi->blkszbits = PAGE_SHIFT; > > > > > if (erofs_is_fscache_mode(sb)) { > > > > > sb->s_blocksize = PAGE_SIZE; > > > > > @@ -704,11 +690,32 @@ static int erofs_fc_fill_super(struct > > > > > super_block *sb, struct fs_context *fc) > > > > > return 0; > > > > > } > > > > > -static int erofs_fc_get_tree(struct fs_context *fc) > > > > > +static void erofs_ctx_to_info(struct fs_context *fc) > > > > > { > > > > > struct erofs_fs_context *ctx = fc->fs_private; > > > > > + struct erofs_sb_info *sbi = fc->s_fs_info; > > > > > + > > > > > + sbi->opt = ctx->opt; > > > > > + sbi->devs = ctx->devs; > > > > > + ctx->devs = NULL; > > > > > + sbi->fsid = ctx->fsid; > > > > > + ctx->fsid = NULL; > > > > > + sbi->domain_id = ctx->domain_id; > > > > > + ctx->domain_id = NULL; > > > > > +} > > > > I'm not sure if abstracting this logic into a seperate helper really > > > > helps understanding the code as the logic itself is quite simple and > > > > easy to be understood. Usually it's a hint of over-abstraction when a > > > > simple helper has only one caller. > > > > > > > Static functions that have only one caller are compiled inline, so we > > > don't have to worry about how that affects the code. > > > > > > The reason these codes are encapsulated in a separate function is so > > > that the code reader understands that these codes are integrated > > > as a whole, and that we shouldn't have to move one or two of these > > > lines individually. > > > > > > But after we get rid of erofs_fs_context, those won't be needed > > > anymore. > > Yeah, I understand. It's only coding style concerns. > > > > > > > Okay, thanks!
I'm fine to get rid of those (erofs_fs_context) as long as the codebase is more clearer and simple. BTW, for the current codebase, I also think it's unneeded to have a separate helper called once without extra actual meaning...
Thanks, Gao Xiang
> > -- > With Best Regards, > Baokun Li
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