linux-ext4 - Re: [PATCH] ext4: limit the number of blocks in one ADD

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Date:   Thu, 9 Sep 2021 09:51:00 -0700
From:   harshad shirwadkar <harshadshirwadkar@...il.com>
To:     Hou Tao <houtao1@...wei.com>
Cc:     "Theodore Y. Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: limit the number of blocks in one ADD_RANGE TLV

Sorry Hou for getting back to you late. This looks good to me.

Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>


On Tue, Sep 7, 2021 at 4:21 AM Hou Tao <houtao1@...wei.com> wrote:
>
> ping ?
>
> On 8/30/2021 3:52 PM, Hou Tao wrote:
> > ping ?
> >
> > On 8/20/2021 12:45 PM, Hou Tao wrote:
> >> Now EXT4_FC_TAG_ADD_RANGE uses ext4_extent to track the
> >> newly-added blocks, but the limit on the max value of
> >> ee_len field is ignored, and it can lead to BUG_ON as
> >> shown below when running command "fallocate -l 128M file"
> >> on a fast_commit-enabled fs:
> >>
> >>   kernel BUG at fs/ext4/ext4_extents.h:199!
> >>   invalid opcode: 0000 [#1] SMP PTI
> >>   CPU: 3 PID: 624 Comm: fallocate Not tainted 5.14.0-rc6+ #1
> >>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
> >>   RIP: 0010:ext4_fc_write_inode_data+0x1f3/0x200
> >>   Call Trace:
> >>    ? ext4_fc_write_inode+0xf2/0x150
> >>    ext4_fc_commit+0x93b/0xa00
> >>    ? ext4_fallocate+0x1ad/0x10d0
> >>    ext4_sync_file+0x157/0x340
> >>    ? ext4_sync_file+0x157/0x340
> >>    vfs_fsync_range+0x49/0x80
> >>    do_fsync+0x3d/0x70
> >>    __x64_sys_fsync+0x14/0x20
> >>    do_syscall_64+0x3b/0xc0
> >>    entry_SYSCALL_64_after_hwframe+0x44/0xae
> >>
> >> Simply fixing it by limiting the number of blocks
> >> in one EXT4_FC_TAG_ADD_RANGE TLV.
> >>
> >> Fixes: aa75f4d3daae ("ext4: main fast-commit commit path")
> >> Signed-off-by: Hou Tao <houtao1@...wei.com>
> >> ---
> >>  fs/ext4/fast_commit.c | 6 ++++++
> >>  1 file changed, 6 insertions(+)
> >>
> >> diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
> >> index e8195229c252..782d05a3f97a 100644
> >> --- a/fs/ext4/fast_commit.c
> >> +++ b/fs/ext4/fast_commit.c
> >> @@ -893,6 +893,12 @@ static int ext4_fc_write_inode_data(struct inode *inode, u32 *crc)
> >>                                          sizeof(lrange), (u8 *)&lrange, crc))
> >>                              return -ENOSPC;
> >>              } else {
> >> +                    unsigned int max = (map.m_flags & EXT4_MAP_UNWRITTEN) ?
> >> +                            EXT_UNWRITTEN_MAX_LEN : EXT_INIT_MAX_LEN;
> >> +
> >> +                    /* Limit the number of blocks in one extent */
> >> +                    map.m_len = min(max, map.m_len);
> >> +
> >>                      fc_ext.fc_ino = cpu_to_le32(inode->i_ino);
> >>                      ex = (struct ext4_extent *)&fc_ext.fc_ex;
> >>                      ex->ee_block = cpu_to_le32(map.m_lblk);
> > .