Messages in this thread | | | Date | Thu, 18 Apr 2024 11:36:03 +0800 | Subject | Re: [PATCH v2] erofs: reliably distinguish block based and fscache mode | From | Baokun Li <> |
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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. > >> 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. >> >> - if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->fsid) >> +static int erofs_fc_get_tree(struct fs_context *fc) >> +{ >> + struct erofs_sb_info *sbi; >> + >> + sbi = kzalloc(sizeof(*sbi), GFP_KERNEL); >> + if (!sbi) >> + return -ENOMEM; >> + >> + fc->s_fs_info = sbi; >> + erofs_ctx_to_info(fc); >> + >> + if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid) >> return get_tree_nodev(fc, erofs_fc_fill_super); >> >> return get_tree_bdev(fc, erofs_fc_fill_super); >> @@ -767,6 +774,7 @@ static void erofs_fc_free(struct fs_context *fc) >> kfree(ctx->fsid); >> kfree(ctx->domain_id); >> kfree(ctx); >> + kfree(fc->s_fs_info); >> } >> >> static const struct fs_context_operations erofs_context_ops = { >> @@ -783,6 +791,7 @@ static int erofs_init_fs_context(struct fs_context *fc) >> ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); >> if (!ctx) >> return -ENOMEM; >> + >> ctx->devs = kzalloc(sizeof(struct erofs_dev_context), GFP_KERNEL); >> if (!ctx->devs) { >> kfree(ctx); >> @@ -799,17 +808,13 @@ static int erofs_init_fs_context(struct fs_context *fc) >> >> static void erofs_kill_sb(struct super_block *sb) >> { >> - struct erofs_sb_info *sbi; >> + struct erofs_sb_info *sbi = EROFS_SB(sb); >> >> - if (erofs_is_fscache_mode(sb)) >> + if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid) >> kill_anon_super(sb); >> else >> kill_block_super(sb); >> >> - sbi = EROFS_SB(sb); >> - if (!sbi) >> - return; >> - >> erofs_free_dev_context(sbi->devs); >> fs_put_dax(sbi->dax_dev, NULL); >> erofs_fscache_unregister_fs(sb); -- With Best Regards, Baokun Li
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