On Wed 15-04-15 11:55:37, Ted Tso wrote: > It looks to me like EXT4_MAXQUOTAS_INIT_BLOCKS includes the credits > neede to set up the quota records. So if we move the call to > dquot_initialize(inode) outside of the normal transaction (which we > should probably do in all cases), that means that we shouldn't ever > need to use EXT4_MAX_QUOTAS_INIT_BLOCKS. Is that right? Correct. EXT4_MAX_QUOTAS_INIT_BLOCKS is only needed if we create the first file for a user. So chown / chgrp may need this and inode creation may need this. As you say, if dquot_init() is in a separate transaction, then inode creation has to account only for a standard quota operation. > The reason why I ask is the following is a easy way to trigger a file > system problem: > > mke2fs -Fq -t ext4 -b 4096 /dev/vdc 50M > mount -t ext4 -o usrquota,grpquota /dev/vdc > l8=12345678 > l16=$l8$l8 > l32=$l16$l16 > l64=$l32$l32 > dmesg -n 7 > ln -s $l64 /vdc/link > > This will result in: > > [ 5.229165] JBD2: ln wants too many credits (156 > 128) > [ 5.230194] EXT4-fs error (device vdc) in __ext4_new_inode:843: error 28 > > In other places where we are allocating a new inode (such as mknod), > we're doing the following: > > credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) + > EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3; > > Which is 37 blocks, and I suspect that's still too darned much. But > if we don't need to use EXT4_MAXQUOTAS_INIT_BLOCKS in ext4_mknod(), we > shouldn't be needing it in ext4_symlink(), either. > > Am I missing anything? Yeah, the credit estimate in ext4_symlink(): credits = 4 + EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) + EXT4_XATTR_TRANS_BLOCKS; is just too pessimistic. Actually what we need for long symlinks is only credits for inode creation + addition to orphan list (so 4 + EXT4_MAXQUOTAS_TRANS_BLOCKS -- sb, gdt, bitmap, inode). Then we stop the transaction and add block to the symlink in a separate transaction. And then we link symlink into a directory in yet another transaction. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
