Messages in this thread | | | Date | Thu, 18 Apr 2024 14:12:39 +0800 | Subject | Re: [PATCH v2] erofs: reliably distinguish block based and fscache mode | From | Baokun Li <> |
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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. >>>> 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!
-- With Best Regards, Baokun Li
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