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When the lazy_itable_init extended option is passed to mke2fs, it considerably speeds up filesystem creation because inode tables are not zeroed out. The fact that parts of the inode table are uninitialized is not a problem so long as the block group descriptors, which contain information regarding how much of the inode table has been initialized, has not been corrupted However, if the block group checksums are not valid, e2fsck must scan the entire inode table, and the the old, uninitialized data could potentially cause e2fsck to report false problems. Hence, it is important for the inode tables to be initialized as soon as possble. This commit adds this feature so that mke2fs can safely use the lazy inode table initialization feature to speed up formatting file systems. This is done via a new new kernel thread called ext4lazyinit, which is created on demand and destroyed, when it is no longer needed. There is only one thread for all ext4 filesystems in the system. When the first filesystem with inititable mount option is mounted, ext4lazyinit thread is created, then the filesystem can register its request in the request list. This thread then walks through the list of requests picking up scheduled requests and invoking ext4_init_inode_table(). Next schedule time for the request is computed by multiplying the time it took to zero out last inode table with wait multiplier, which can be set with the (init_itable=n) mount option (default is 10). We are doing this so we do not take the whole I/O bandwidth. When the thread is no longer necessary (request list is empty) it frees the appropriate structures and exits (and can be created later later by another filesystem). We do not disturb regular inode allocations in any way, it just do not care whether the inode table is, or is not zeroed. But when zeroing, we have to skip used inodes, obviously. Also we should prevent new inode allocations from the group, while zeroing is on the way. For that we take write alloc_sem lock in ext4_init_inode_table() and read alloc_sem in the ext4_claim_inode, so when we are unlucky and allocator hits the group which is currently being zeroed, it just has to wait. This can be suppresed using the mount option no_init_itable. Signed-off-by: Lukas Czerner <lczerner@redhat.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> |
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| .. | ||
| caching | ||
| configfs | ||
| nfs | ||
| pohmelfs | ||
| 9p.txt | ||
| 00-INDEX | ||
| adfs.txt | ||
| affs.txt | ||
| afs.txt | ||
| autofs4-mount-control.txt | ||
| automount-support.txt | ||
| befs.txt | ||
| bfs.txt | ||
| btrfs.txt | ||
| ceph.txt | ||
| cifs.txt | ||
| coda.txt | ||
| cramfs.txt | ||
| debugfs.txt | ||
| dentry-locking.txt | ||
| devpts.txt | ||
| directory-locking | ||
| dlmfs.txt | ||
| dnotify_test.c | ||
| dnotify.txt | ||
| ecryptfs.txt | ||
| exofs.txt | ||
| ext2.txt | ||
| ext3.txt | ||
| ext4.txt | ||
| fiemap.txt | ||
| files.txt | ||
| fuse.txt | ||
| gfs2-glocks.txt | ||
| gfs2-uevents.txt | ||
| gfs2.txt | ||
| hfs.txt | ||
| hfsplus.txt | ||
| hpfs.txt | ||
| inotify.txt | ||
| isofs.txt | ||
| jfs.txt | ||
| Locking | ||
| locks.txt | ||
| logfs.txt | ||
| Makefile | ||
| mandatory-locking.txt | ||
| ncpfs.txt | ||
| nilfs2.txt | ||
| ntfs.txt | ||
| ocfs2.txt | ||
| omfs.txt | ||
| porting | ||
| proc.txt | ||
| quota.txt | ||
| ramfs-rootfs-initramfs.txt | ||
| relay.txt | ||
| romfs.txt | ||
| seq_file.txt | ||
| sharedsubtree.txt | ||
| smbfs.txt | ||
| spufs.txt | ||
| squashfs.txt | ||
| sysfs-pci.txt | ||
| sysfs-tagging.txt | ||
| sysfs.txt | ||
| sysv-fs.txt | ||
| tmpfs.txt | ||
| ubifs.txt | ||
| udf.txt | ||
| ufs.txt | ||
| vfat.txt | ||
| vfs.txt | ||
| xfs-delayed-logging-design.txt | ||
| xfs.txt | ||
| xip.txt | ||