From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 460733290C9 for ; Wed, 14 Oct 2026 03:13:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791947629; cv=none; b=aRC6yPZSrQ9cKvFOpek7Ia372ypEgqgPEctmXTIxFHrwtBwvlxudhm4iTY4gd/5uxilyBOsqABx/gjmoNNvPQlBydeHQSvdhw5m/QFnBR1f0/euhlf1NqLvtN3bWYe4Q3T3kWs8U5FFmJaQASAnbiWeRdxd42PwfSxQYnXgqQho= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791947629; c=relaxed/simple; bh=HudLhD0OEw45OIUCnZ46zOrxuKohOBD1HI/TilXIe/E=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=X2ipG6jx1tZkmI/tDn0mo0rQKYhUpmDQnrrlxzeyUzf/fJifz9qK7hU8TXqu4p1+fZ5WRWcJAKfpE/113Y7jiu1oMT9cm25xfyZhEWJPOgY8m9ebAclsvjjAUbKfP55odORWFuNkO3M1gIyQ8ehNlgdanRqSGic/THMfTGKSqeo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KrNsDeVw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KrNsDeVw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8E9051F00893; Wed, 14 Oct 2026 03:13:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791947626; bh=pub0y8/eoX3u6lTe1/WCKzlMffQUWwOp2wu7xbPFAYM=; h=Date:Cc:Subject:To:References:From:In-Reply-To; b=KrNsDeVwKSwLc0W7EME5yDMHrIx7hnSaZF+nbP8ZTDLZgOjOsuhKj0tgpxHO/aQ2t tK5skJI8eEQnr51Z3qg75i/xrR48FqrEScGjAgEF7NwGVIx6aPwoKx9KhIXzKIm+ek 47cOkgEANUZUQgaxXSaj1bhafC5aN2lZp+gmnDDrrYoXh2pKyabqOaF2qnDGfq3JdX h+XixlS2teJC+xy0hC2t4A/mYCSsLKRUn/sRxkTuvvgZ3JQoXToxCKliGDiJj725iv 4bETMx+7aur7T+xtTW421Hloj+vTk0AWX73BUoFppxZcptZpXKkZsNsxo6NpGKoBz0 cIPBTCNg30y6g== Message-ID: <0aedc5af-1273-4510-a8fa-5ddf2281b699@kernel.org> Date: Wed, 14 Oct 2026 11:13:43 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, Daeho Jeong Subject: Re: [f2fs-dev] [PATCH v2 2/2] f2fs: introduce reserve_shrink mount option for filesystem shrinkage To: Daeho Jeong References: <20260911143549.909867-1-daeho43@gmail.com> <20260911143549.909867-2-daeho43@gmail.com> <3e5f2bd4-f0e6-4f79-b182-6cb8ac331580@kernel.org> Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/14/26 07:27, Daeho Jeong wrote: > On Tue, Oct 13, 2026 at 8:36 AM Daeho Jeong wrote: >> >> On Mon, Oct 12, 2026 at 7:15 PM Daeho Jeong wrote: >>> >>> On Mon, Oct 12, 2026 at 6:27 PM Chao Yu wrote: >>>> >>>> On 9/15/26 00:24, Daeho Jeong wrote: >>>>> On Mon, Sep 14, 2026 at 12:15 AM Chao Yu wrote: >>>>>> >>>>>> On 9/11/26 22:35, Daeho Jeong wrote: >>>>>>> From: Daeho Jeong >>>>>>> >>>>>>> When preparing for subsequent online filesystem shrinkage (e.g., during >>>>>>> partition resizing or FOTA updates), sufficient free space must be >>>>>>> preserved so that valid data blocks can be evacuated and the filesystem >>>>>>> can safely shrink. >>>>>>> >>>>>>> Existing reserve_root cannot prevent space exhaustion by privileged root >>>>>>> processes (such as OTA updaters, package managers, and system daemons >>>>>>> running with CAP_SYS_RESOURCE), which can allocate blocks from the root >>>>>>> reserve and lead to resize failures due to lack of space. Moreover, >>>>>> >>>>>> I'm thinking about reusing existing mount option AMAP, is there any problem >>>>>> to use "reserve_root=" w/ 128mb+shrunk_size_mb when we execute online filesyste >>>>>> shrinkage? once it is done, recover w/ reserve_root=128mb. >>>>>> >>>>>>> runtime configurable reserved_blocks represents permanent GC and metadata >>>>>>> headroom that must persist after resize, which would cause double-counting >>>>>>> if inflated for shrinkage. >>>>>> >>>>>> I didn't get it, can you please explain a bit more about this issue? >>>>>> >>>>>> Thanks, >>>>> >>>>> Hi Chao, >>>>> >>>>> There are three main reasons why reserve_root cannot be reused: >>>>> >>>>> 1. Double-counting in f2fs_resize_fs(): >>>>> f2fs_resize_fs() checks: >>>>> shrunk_blocks + valid_user_blocks + root_reserved_blocks + ... > >>>>> user_block_count >>>>> Since root_reserved_blocks must persist after >>>>> resize, inflating it by shrunk_size causes shrunk_size to be counted twice, >>>>> requiring 2x free space and triggering false -ENOSPC. Resetting it right before >>>>> resize also introduces a race window where concurrent writes can >>>>> consume the space. >>>>> 2. Root can allocate from reserve_root: >>>>> reserve_root allows root/CAP_SYS_RESOURCE processes to allocate. During OTA, >>>>> system daemons and updaters can eat into the reserved blocks. >>>>> reserve_shrink strictly blocks all callers, including root. >>>> >>>> Daeho, sorry for the delay. >>>> >>>> Thanks for the explanation, I see, it's not appropriate to reuse >>>> "reserve_root=" option for your requirement. >>>> >>>> May I ask that do you need to keep the reservation for a long time before resize, >>>> e.g. from OTA starts till shrink happens? or is it enough to make it reserved >>>> during f2fs_resize_fs()? >>>> >>>> If the latter, can we just reserve shrunk_blocks in f2fs_resize_fs() >>>> directly, w/ the same way we did for f2fs_ioc_reserve_dev_alias()? Then >>>> we don't need a new mount option. Something like: >>>> >>>> f2fs_resize_fs() >>>> spin_lock(&sbi->stat_lock); >>>> if (shrunk_blocks + valid_user_blocks(sbi) + ... > sbi->user_block_count) >>>> err = -ENOSPC; >>>> else >>>> sbi->resize_reserved_blocks += shrunk_blocks; >>>> spin_unlock(&sbi->stat_lock); >>>> >>>> free_segment_range(sbi, secs, true); >>>> ... >>>> freeze_super(); >>>> ... >>>> spin_lock(&sbi->stat_lock); >>>> sbi->user_block_count -= shrunk_blocks; >>>> sbi->resize_reserved_blocks -= shrunk_blocks; >>>> spin_unlock(&sbi->stat_lock); >>>> ... >>>> /* error path: sbi->resize_reserved_blocks -= shrunk_blocks */ >>>> >>>> and in get_available_block_count(), deduct resize_reserved_blocks as we did for >>>> alias_reserved_blocks, so that no one, including root, can allocate from the >>>> reserved space during resize. >>>> >>>> Thanks, >>> >>> Hi Chao, >>> >>> Thanks for the suggestion. >>> >>> Unfortunately, reserving only inside f2fs_resize_fs() is not enough for >>> our use case. We need the reservation to be in place for a long time >>> before the resize, i.e. from the moment we decide to shrink (mount time) >>> until F2FS_IOC_RESIZE_FS is actually issued. During that window, >>> privileged processes (OTA updater, package manager, system daemons) keep >>> writing to the filesystem. If they consume the free space, the ENOSPC >>> check at the entry of f2fs_resize_fs() fails right away, so there is no >>> chance to reserve anything inside the ioctl. Also, statfs would keep >>> reporting space that is going to be cut off. >>> >>> That's why it's a mount option: the reservation is applied before any >>> userspace write can happen, it's honored for all callers including root, >>> it's reflected in statfs, and it's released automatically once the >>> shrink succeeds. >>> >>> Thanks, >> >> Plus, >> >> Please think about the FOTA scenario below: >> >> 1) The device downloads the FOTA image. At this point, we check that >> there is enough free space for the shrink. >> 2) The device reboots to apply the update. >> 3) After the reboot, /data is mounted and F2FS_IOC_RESIZE_FS is issued >> to shrink the filesystem. >> >> Between 1) and 3), there is a long window that also spans a reboot. >> >> Thanks, > > Hi Chao, > > Sorry for the confusion. Our scenario has recently changed. > > Now the shrink is triggered at OTA install time, before the reboot: the > updater figures out how much space the new partitions need, and issues > F2FS_IOC_RESIZE_FS on the mounted /data right away. So we don't need to > keep the reservation for a long time before the resize anymore. What we > need is to protect the space during f2fs_resize_fs(), between the > dry-run GC and freeze_super(), where other processes (including root) > can consume it. > > So your suggestion fits the new scenario better. I'll drop the > reserve_shrink mount option, and send a new patch that reserves > shrunk_blocks inside f2fs_resize_fs() and deducts it in > get_available_block_count() for all callers. Hi Daeho, I see, thanks for the sync-up. BTW, could you please add above background information into commit message? I think it can help developer/reviewer to know more background info. Thanks, > > Thanks for the review, > >> >>> >>>> >>>>> >>>>> Thanks, >>>>> Daeho >>>>> >>>>>> >>>>>>> >>>>>>> To resolve this, introduce a dedicated reserve_shrink= >>>>>>> mount option: >>>>>>> 1. Symmetrically mirrors reserve_root= in block units to >>>>>>> pre-reserve space specifically for subsequent filesystem shrinkage. >>>>>>> 2. In get_available_block_count(), unconditionally deducts >>>>>>> reserve_shrink_blocks for all callers, strictly rejecting all >>>>>>> allocations (including root / CAP_SYS_RESOURCE) once available blocks >>>>>>> are exhausted. >>>>>>> 3. In f2fs_statfs(), deducts reserve_shrink_blocks from f_bfree (and >>>>>>> f_bavail) so that filesystem statistics accurately reflect usable space. >>>>>>> 4. In f2fs_resize_fs(), automatically resets reserve_shrink_blocks to 0 >>>>>>> and clears F2FS_MOUNT_RESERVE_SHRINK upon successful shrink completion, >>>>>>> releasing any remaining reservation. >>>>>>> 5. In sysfs: reserved_blocks, subtracts reserve_shrink_blocks when >>>>>>> validating the upper limit of configurable reserved blocks. >>>>>>> >>>>>>> Signed-off-by: Daeho Jeong >>>>>>> --- >>>>>>> v2: >>>>>>> - Split out mount option bitmask expansion (BIT_ULL) into a separate >>>>>>> prerequisite patch (Patch 1/2). >>>>>>> --- >>>>>>> Documentation/filesystems/f2fs.rst | 7 +++++ >>>>>>> fs/f2fs/f2fs.h | 9 ++++++ >>>>>>> fs/f2fs/gc.c | 5 ++++ >>>>>>> fs/f2fs/super.c | 47 ++++++++++++++++++++++++++++++ >>>>>>> fs/f2fs/sysfs.c | 13 +++++++-- >>>>>>> 5 files changed, 79 insertions(+), 2 deletions(-) >>>>>>> >>>>>>> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst >>>>>>> index 771216f45207..dbdc5d5a83ad 100644 >>>>>>> --- a/Documentation/filesystems/f2fs.rst >>>>>>> +++ b/Documentation/filesystems/f2fs.rst >>>>>>> @@ -191,6 +191,13 @@ reserve_node=%d Support configuring reserved nodes which are used for >>>>>>> gid, the default limit is 12.5% of all nodes. >>>>>>> resuid=%d The user ID which may use the reserved blocks and nodes. >>>>>>> resgid=%d The group ID which may use the reserved blocks and nodes. >>>>>>> +reserve_shrink=%d Support pre-reserving space for subsequent filesystem >>>>>>> + shrinkage (e.g. during partition resizing or FOTA), >>>>>>> + unit: blocks. Unlike reserve_root, allocations from >>>>>>> + this reserved space strictly reject all callers >>>>>>> + (including root / CAP_SYS_RESOURCE). Once the >>>>>>> + filesystem is successfully shrunk via resize, this >>>>>>> + value is automatically reset to 0. >>>>>>> fault_injection=%d Enable fault injection in all supported types with >>>>>>> specified injection rate. >>>>>>> fault_type=%d Support configuring fault injection type, should be >>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h >>>>>>> index 4aaf29de3f6f..48a91771be95 100644 >>>>>>> --- a/fs/f2fs/f2fs.h >>>>>>> +++ b/fs/f2fs/f2fs.h >>>>>>> @@ -145,6 +145,7 @@ enum f2fs_mount_opt { >>>>>>> */ >>>>>>> F2FS_MOUNT_LAZYTIME, >>>>>>> F2FS_MOUNT_RESERVE_NODE, >>>>>>> + F2FS_MOUNT_RESERVE_SHRINK, >>>>>>> }; >>>>>>> >>>>>>> #define F2FS_OPTION(sbi) ((sbi)->mount_opt) >>>>>>> @@ -226,6 +227,7 @@ struct f2fs_mount_info { >>>>>>> unsigned long long opt; >>>>>>> block_t root_reserved_blocks; /* root reserved blocks */ >>>>>>> block_t root_reserved_nodes; /* root reserved nodes */ >>>>>>> + block_t reserve_shrink_blocks; /* reserve blocks for shrink */ >>>>>>> kuid_t s_resuid; /* reserved blocks for uid */ >>>>>>> kgid_t s_resgid; /* reserved blocks for gid */ >>>>>>> int active_logs; /* # of active logs */ >>>>>>> @@ -2658,6 +2660,13 @@ static inline unsigned int get_available_block_count(struct f2fs_sb_info *sbi, >>>>>>> if (test_opt(sbi, RESERVE_ROOT) && !__allow_reserved_root(sbi, inode, cap)) >>>>>>> avail_user_block_count -= F2FS_OPTION(sbi).root_reserved_blocks; >>>>>>> >>>>>>> + if (test_opt(sbi, RESERVE_SHRINK)) { >>>>>>> + if (avail_user_block_count > F2FS_OPTION(sbi).reserve_shrink_blocks) >>>>>>> + avail_user_block_count -= F2FS_OPTION(sbi).reserve_shrink_blocks; >>>>>>> + else >>>>>>> + avail_user_block_count = 0; >>>>>>> + } >>>>>>> + >>>>>>> if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) { >>>>>>> if (avail_user_block_count > sbi->unusable_block_count) >>>>>>> avail_user_block_count -= sbi->unusable_block_count; >>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>>>>>> index bc22dde1cb30..556c4793478d 100644 >>>>>>> --- a/fs/f2fs/gc.c >>>>>>> +++ b/fs/f2fs/gc.c >>>>>>> @@ -2492,6 +2492,11 @@ int f2fs_resize_fs(struct file *filp, __u64 block_count) >>>>>>> spin_lock(&sbi->stat_lock); >>>>>>> sbi->user_block_count += shrunk_blocks; >>>>>>> spin_unlock(&sbi->stat_lock); >>>>>>> + } else if (test_opt(sbi, RESERVE_SHRINK)) { >>>>>>> + spin_lock(&sbi->stat_lock); >>>>>>> + F2FS_OPTION(sbi).reserve_shrink_blocks = 0; >>>>>>> + clear_opt(sbi, RESERVE_SHRINK); >>>>>>> + spin_unlock(&sbi->stat_lock); >>>>>>> } >>>>>>> out_err: >>>>>>> f2fs_up_write_trace(&sbi->cp_global_sem, &clc); >>>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c >>>>>>> index a5e109bdcebc..58f33750b2a8 100644 >>>>>>> --- a/fs/f2fs/super.c >>>>>>> +++ b/fs/f2fs/super.c >>>>>>> @@ -196,6 +196,7 @@ enum { >>>>>>> Opt_data_flush, >>>>>>> Opt_reserve_root, >>>>>>> Opt_reserve_node, >>>>>>> + Opt_reserve_shrink, >>>>>>> Opt_resgid, >>>>>>> Opt_resuid, >>>>>>> Opt_mode, >>>>>>> @@ -328,6 +329,7 @@ static const struct fs_parameter_spec f2fs_param_specs[] = { >>>>>>> fsparam_flag("data_flush", Opt_data_flush), >>>>>>> fsparam_u32("reserve_root", Opt_reserve_root), >>>>>>> fsparam_u32("reserve_node", Opt_reserve_node), >>>>>>> + fsparam_u32("reserve_shrink", Opt_reserve_shrink), >>>>>>> fsparam_gid("resgid", Opt_resgid), >>>>>>> fsparam_uid("resuid", Opt_resuid), >>>>>>> fsparam_enum("mode", Opt_mode, f2fs_param_mode), >>>>>>> @@ -407,6 +409,7 @@ static match_table_t f2fs_checkpoint_tokens = { >>>>>>> #define F2FS_SPEC_lookup_mode (1 << 24) >>>>>>> #define F2FS_SPEC_reserve_node (1 << 25) >>>>>>> #define F2FS_SPEC_resizable_tail_secno (1 << 26) >>>>>>> +#define F2FS_SPEC_reserve_shrink (1 << 27) >>>>>>> >>>>>>> struct f2fs_fs_context { >>>>>>> struct f2fs_mount_info info; >>>>>>> @@ -550,6 +553,27 @@ static inline void limit_reserve_root(struct f2fs_sb_info *sbi) >>>>>>> F2FS_OPTION(sbi).s_resgid)); >>>>>>> } >>>>>>> >>>>>>> +static inline void limit_reserve_shrink(struct f2fs_sb_info *sbi) >>>>>>> +{ >>>>>>> + block_t block_limit; >>>>>>> + >>>>>>> + if (!test_opt(sbi, RESERVE_SHRINK)) >>>>>>> + return; >>>>>>> + >>>>>>> + block_limit = sbi->user_block_count - sbi->reserved_blocks; >>>>>>> + if (test_opt(sbi, RESERVE_ROOT)) { >>>>>>> + if (block_limit > F2FS_OPTION(sbi).root_reserved_blocks) >>>>>>> + block_limit -= F2FS_OPTION(sbi).root_reserved_blocks; >>>>>>> + else >>>>>>> + block_limit = 0; >>>>>>> + } >>>>>>> + if (F2FS_OPTION(sbi).reserve_shrink_blocks > block_limit) { >>>>>>> + F2FS_OPTION(sbi).reserve_shrink_blocks = block_limit; >>>>>>> + f2fs_info(sbi, "Reduce reserved blocks for shrink = %u", >>>>>>> + F2FS_OPTION(sbi).reserve_shrink_blocks); >>>>>>> + } >>>>>>> +} >>>>>>> + >>>>>>> static inline void adjust_unusable_cap_perc(struct f2fs_sb_info *sbi) >>>>>>> { >>>>>>> if (!F2FS_OPTION(sbi).unusable_cap_perc) >>>>>>> @@ -953,6 +977,14 @@ static int f2fs_parse_param(struct fs_context *fc, struct fs_parameter *param) >>>>>>> F2FS_CTX_INFO(ctx).root_reserved_nodes = result.uint_32; >>>>>>> ctx->spec_mask |= F2FS_SPEC_reserve_node; >>>>>>> break; >>>>>>> + case Opt_reserve_shrink: >>>>>>> + if (result.uint_32) >>>>>>> + ctx_set_opt(ctx, F2FS_MOUNT_RESERVE_SHRINK); >>>>>>> + else >>>>>>> + ctx_clear_opt(ctx, F2FS_MOUNT_RESERVE_SHRINK); >>>>>>> + F2FS_CTX_INFO(ctx).reserve_shrink_blocks = result.uint_32; >>>>>>> + ctx->spec_mask |= F2FS_SPEC_reserve_shrink; >>>>>>> + break; >>>>>>> case Opt_resuid: >>>>>>> F2FS_CTX_INFO(ctx).s_resuid = result.uid; >>>>>>> ctx->spec_mask |= F2FS_SPEC_resuid; >>>>>>> @@ -1775,6 +1807,9 @@ static void f2fs_apply_options(struct fs_context *fc, struct super_block *sb) >>>>>>> if (ctx->spec_mask & F2FS_SPEC_reserve_node) >>>>>>> F2FS_OPTION(sbi).root_reserved_nodes = >>>>>>> F2FS_CTX_INFO(ctx).root_reserved_nodes; >>>>>>> + if (ctx->spec_mask & F2FS_SPEC_reserve_shrink) >>>>>>> + F2FS_OPTION(sbi).reserve_shrink_blocks = >>>>>>> + F2FS_CTX_INFO(ctx).reserve_shrink_blocks; >>>>>>> if (ctx->spec_mask & F2FS_SPEC_resgid) >>>>>>> F2FS_OPTION(sbi).s_resgid = F2FS_CTX_INFO(ctx).s_resgid; >>>>>>> if (ctx->spec_mask & F2FS_SPEC_resuid) >>>>>>> @@ -2300,6 +2335,13 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) >>>>>>> buf->f_bfree = user_block_count - valid_user_blocks(sbi) - >>>>>>> sbi->current_reserved_blocks; >>>>>>> >>>>>>> + if (test_opt(sbi, RESERVE_SHRINK)) { >>>>>>> + if (buf->f_bfree > F2FS_OPTION(sbi).reserve_shrink_blocks) >>>>>>> + buf->f_bfree -= F2FS_OPTION(sbi).reserve_shrink_blocks; >>>>>>> + else >>>>>>> + buf->f_bfree = 0; >>>>>>> + } >>>>>>> + >>>>>>> if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) >>>>>>> buf->f_bfree = 0; >>>>>>> else >>>>>>> @@ -2524,6 +2566,9 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root) >>>>>>> F2FS_OPTION(sbi).s_resuid), >>>>>>> from_kgid_munged(&init_user_ns, >>>>>>> F2FS_OPTION(sbi).s_resgid)); >>>>>>> + if (test_opt(sbi, RESERVE_SHRINK)) >>>>>>> + seq_printf(seq, ",reserve_shrink=%u", >>>>>>> + F2FS_OPTION(sbi).reserve_shrink_blocks); >>>>>>> #ifdef CONFIG_F2FS_FAULT_INJECTION >>>>>>> if (test_opt(sbi, FAULT_INJECTION)) { >>>>>>> seq_printf(seq, ",fault_injection=%u", >>>>>>> @@ -3105,6 +3150,7 @@ static int __f2fs_remount(struct fs_context *fc, struct super_block *sb) >>>>>>> >>>>>>> adjust_pinned_area_boundary(sbi); >>>>>>> limit_reserve_root(sbi); >>>>>>> + limit_reserve_shrink(sbi); >>>>>>> fc->sb_flags = (flags & ~SB_LAZYTIME) | (sb->s_flags & SB_LAZYTIME); >>>>>>> >>>>>>> sbi->umount_lock_holder = NULL; >>>>>>> @@ -5322,6 +5368,7 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc) >>>>>>> sbi->current_reserved_blocks = 0; >>>>>>> sbi->alias_reserved_blocks = 0; >>>>>>> limit_reserve_root(sbi); >>>>>>> + limit_reserve_shrink(sbi); >>>>>>> adjust_unusable_cap_perc(sbi); >>>>>>> >>>>>>> f2fs_init_extent_cache_info(sbi); >>>>>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c >>>>>>> index aaca9ed9b169..d61940d095b4 100644 >>>>>>> --- a/fs/f2fs/sysfs.c >>>>>>> +++ b/fs/f2fs/sysfs.c >>>>>>> @@ -591,9 +591,18 @@ static ssize_t __sbi_store(struct f2fs_attr *a, >>>>>>> } >>>>>>> #endif >>>>>>> if (a->struct_type == RESERVED_BLOCKS) { >>>>>>> + unsigned long limit; >>>>>>> + >>>>>>> spin_lock(&sbi->stat_lock); >>>>>>> - if (t > (unsigned long)(sbi->user_block_count - >>>>>>> - F2FS_OPTION(sbi).root_reserved_blocks)) { >>>>>>> + limit = sbi->user_block_count - >>>>>>> + F2FS_OPTION(sbi).root_reserved_blocks; >>>>>>> + if (test_opt(sbi, RESERVE_SHRINK)) { >>>>>>> + if (limit > F2FS_OPTION(sbi).reserve_shrink_blocks) >>>>>>> + limit -= F2FS_OPTION(sbi).reserve_shrink_blocks; >>>>>>> + else >>>>>>> + limit = 0; >>>>>>> + } >>>>>>> + if (t > limit) { >>>>>>> spin_unlock(&sbi->stat_lock); >>>>>>> return -EINVAL; >>>>>>> } >>>>>> >>>>