I agree that we need to deciede which inode numbers to use for special
system file. Anyway, I will use the first way in the next version of
patch.
On Tue, Apr 21, 2015 at 8:35 PM, Jan Kara <jack@xxxxxxx> wrote:
> On Mon 20-04-15 17:27:20, Andreas Dilger wrote:
>> On Apr 19, 2015, at 7:39 PM, Li Xi <pkuelelixi@xxxxxxxxx> wrote:
> ...
>> > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> > index 1446c4f..a7acf10 100644
>> > --- a/fs/ext4/ext4.h
>> > +++ b/fs/ext4/ext4.h
>> > @@ -1169,7 +1169,8 @@ struct ext4_super_block {
>> > __le32 s_overhead_clusters; /* overhead blocks/clusters in fs */
>> > __le32 s_backup_bgs[2]; /* groups with sparse_super2 SBs */
>> > __u8 s_encrypt_algos[4]; /* Encryption algorithms in use */
>> > - __le32 s_reserved[105]; /* Padding to the end of the block */
>> > + __le32 s_prj_quota_inum; /* inode for tracking project quota */
>> > + __le32 s_reserved[104]; /* Padding to the end of the block */
>> > __le32 s_checksum; /* crc32c(superblock) */
>> > };
>> >
>> > @@ -1184,7 +1185,7 @@ struct ext4_super_block {
>> > #define EXT4_MF_FS_ABORTED 0x0002 /* Fatal error detected */
>> >
>> > /* Number of quota types we support */
>> > -#define EXT4_MAXQUOTAS 2
>> > +#define EXT4_MAXQUOTAS 3
>> >
>> > /*
>> > * fourth extended-fs super-block data in memory
>> > @@ -1376,6 +1377,7 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
>> > ino == EXT4_BOOT_LOADER_INO ||
>> > ino == EXT4_JOURNAL_INO ||
>> > ino == EXT4_RESIZE_INO ||
>> > + ino == le32_to_cpu(EXT4_SB(sb)->s_es->s_prj_quota_inum) ||
>>
>> This extra check isn't needed, since s_proj_quota_inum will be a regular
>> inode number and handled by the checks below.
> So I think this needs a final decision from Ted how we handle new system
> files and use it consistently among all features - project quotas, orphan
> file, etc. Ted, can you share your thoughts please? Options are:
>
> 1) We allocate inodes from normal inode pool and just store their inode
> numbers in superblock.
> + no need to increase number of special inodes
> - slightly less robust since inode can be anywhere
> - needs special treatment from fsck to know inode isn't just some lost inode
> - consumes space in sb for inode numbers
>
> 2) Like 1) but also create special "system" directory and attach system
> inodes there
> + fsck just needs to know about the system directory, not about every
> special file
> + no wasted space in sb for every special inode
> - more code in kernel to implement this
> - even less robust than 1) - when system directory gets corrupt, we are in
> trouble
>
> 3) Increase number of special inodes
> + consistent with what we did upto now
> + somewhat more robust since inode is in fixed place
> - tune2fs needs to do quite some work to reserve more inodes
> - wastes unused special inodes
>
> Honza
> --
> Jan Kara <jack@xxxxxxx>
> SUSE Labs, CR
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