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SubjectRe: [PATCH v4] Revert "f2fs crypto: avoid unneeded memory allocation in ->readdir"
On 02/28, Chao Yu wrote:
> Hi Jaegeuk,
>
> On 2018/2/28 13:48, Jaegeuk Kim wrote:
> > Hi Yunlong,
> >
> > As Eric pointed out, how do you think using nohighmem for directory likewise
>
> I'd like to ask, at the beginning, why we choose to use highmem for dentry page?
> any history reason there?

There was no huge preference on it based on performance. I just wanted not to
abuse lowmem.

Thanks,

>
> > ext4, which looks like more efficient? Actually, we don't need to do this in
> > most of recent kernels, right?
>
> It's OK to me to keep a line with ext4.
>
> Thanks,
>
> >
> > Thanks,
> >
> > On 02/28, Yunlong Song wrote:
> >> This reverts commit e06f86e61d7a67fe6e826010f57aa39c674f4b1b.
> >>
> >> Conflicts:
> >> fs/f2fs/dir.c
> >>
> >> In some platforms (such as arm), high memory is used, then the
> >> decrypting filename will cause panic, the reason see commit
> >> 569cf1876a32e574ba8a7fb825cd91bafd003882 ("f2fs crypto: allocate buffer
> >> for decrypting filename"):
> >>
> >> We got dentry pages from high_mem, and its address space directly goes into the
> >> decryption path via f2fs_fname_disk_to_usr.
> >> But, sg_init_one assumes the address is not from high_mem, so we can get this
> >> panic since it doesn't call kmap_high but kunmap_high is triggered at the end.
> >>
> >> kernel BUG at ../../../../../../kernel/mm/highmem.c:290!
> >> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
> >> ...
> >> (kunmap_high+0xb0/0xb8) from [<c0114534>] (__kunmap_atomic+0xa0/0xa4)
> >> (__kunmap_atomic+0xa0/0xa4) from [<c035f028>] (blkcipher_walk_done+0x128/0x1ec)
> >> (blkcipher_walk_done+0x128/0x1ec) from [<c0366c24>] (crypto_cbc_decrypt+0xc0/0x170)
> >> (crypto_cbc_decrypt+0xc0/0x170) from [<c0367148>] (crypto_cts_decrypt+0xc0/0x114)
> >> (crypto_cts_decrypt+0xc0/0x114) from [<c035ea98>] (async_decrypt+0x40/0x48)
> >> (async_decrypt+0x40/0x48) from [<c032ca34>] (f2fs_fname_disk_to_usr+0x124/0x304)
> >> (f2fs_fname_disk_to_usr+0x124/0x304) from [<c03056fc>] (f2fs_fill_dentries+0xac/0x188)
> >> (f2fs_fill_dentries+0xac/0x188) from [<c03059c8>] (f2fs_readdir+0x1f0/0x300)
> >> (f2fs_readdir+0x1f0/0x300) from [<c0218054>] (vfs_readdir+0x90/0xb4)
> >> (vfs_readdir+0x90/0xb4) from [<c0218418>] (SyS_getdents64+0x64/0xcc)
> >> (SyS_getdents64+0x64/0xcc) from [<c0105ba0>] (ret_fast_syscall+0x0/0x30)
> >>
> >> Howerver, later patch:
> >> commit e06f86e61d7a ("f2fs crypto: avoid unneeded memory allocation in ->readdir")
> >> reverts the codes, which causes panic again in arm, so fix it back to the old version.
> >>
> >> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> >> Reviewed-by: Chao Yu <yuchao0@huawei.com>
> >> ---
> >> fs/f2fs/dir.c | 7 +++++++
> >> 1 file changed, 7 insertions(+)
> >>
> >> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> >> index f00b5ed..de2e295 100644
> >> --- a/fs/f2fs/dir.c
> >> +++ b/fs/f2fs/dir.c
> >> @@ -825,9 +825,16 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
> >> int save_len = fstr->len;
> >> int err;
> >>
> >> + de_name.name = f2fs_kmalloc(sbi, de_name.len, GFP_NOFS);
> >> + if (!de_name.name)
> >> + return -ENOMEM;
> >> +
> >> + memcpy(de_name.name, d->filename[bit_pos], de_name.len);
> >> +
> >> err = fscrypt_fname_disk_to_usr(d->inode,
> >> (u32)de->hash_code, 0,
> >> &de_name, fstr);
> >> + kfree(de_name.name);
> >> if (err)
> >> return err;
> >>
> >> --
> >> 1.8.5.2
> >
> > .
> >

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