Messages in this thread | | | Date | Thu, 18 Apr 2024 13:50:30 +0800 | Subject | Re: [PATCH v2] erofs: reliably distinguish block based and fscache mode | From | Jingbo Xu <> |
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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.
>> >>> 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.
-- Thanks, Jingbo
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