On Wed 06-04-22 16:45:03, Zhang Yi wrote: > Symlink's external data block is one kind of metadata block, and now > that almost all ext4 metadata block's page cache (e.g. directory blocks, > quota blocks...) belongs to bdev backing inode except the symlink. It > is essentially worked in data=journal mode like other regular file's > data block because probably in order to make it simple for generic VFS > code handling symlinks or some other historical reasons, but the logic > of creating external data block in ext4_symlink() is complicated. and it > also make things confused if user do not want to let the filesystem > worked in data=journal mode. This patch convert the final exceptional > case and make things clean, move the mapping of the symlink's external > data block to bdev like any other metadata block does. > > Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx> > --- > This RFC patch follow the talking of whether if we could unify the > journal mode of ext4 metadata blocks[1], it stop using the data=journal > mode for the final exception case of symlink's external data block. Any > comments are welcome, thanks. > > [1]. https://lore.kernel.org/linux-ext4/20220321151141.hypnhr6o4vng2sa6@xxxxxxxxxx/T/#m84b942a6bb838ba60ae8afd906ebbb987a577488 > > fs/ext4/inode.c | 9 +--- > fs/ext4/namei.c | 123 +++++++++++++++++++++------------------------- > fs/ext4/symlink.c | 44 ++++++++++++++--- > 3 files changed, 93 insertions(+), 83 deletions(-) Hum, we don't save on code but I'd say the result is somewhat more standard. So I guess this makes some sense. Let's see what Ted thinks... Otherwise I've found just one small bug below. > @@ -3270,26 +3296,8 @@ static int ext4_symlink(struct user_namespace *mnt_userns, struct inode *dir, > if (err) > return err; > > - if ((disk_link.len > EXT4_N_BLOCKS * 4)) { > - /* > - * For non-fast symlinks, we just allocate inode and put it on > - * orphan list in the first transaction => we need bitmap, > - * group descriptor, sb, inode block, quota blocks, and > - * possibly selinux xattr blocks. > - */ > - credits = 4 + EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) + > - EXT4_XATTR_TRANS_BLOCKS; > - } else { > - /* > - * Fast symlink. We have to add entry to directory > - * (EXT4_DATA_TRANS_BLOCKS + EXT4_INDEX_EXTRA_TRANS_BLOCKS), > - * allocate new inode (bitmap, group descriptor, inode block, > - * quota blocks, sb is already counted in previous macros). > - */ > - credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) + > - EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3; > - } > - > + credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) + > + EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3; This does not seem like enough credits - we may need to allocate inode, add entry to directory, allocate & initialize symlink block. So I think you need to add 4 for block allocation + init in case of non-fast symlink. And please keep the comment explaining what is actually counted in the number of credits... Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
