mirror of
https://github.com/fail0verflow/switch-linux.git
synced 2025-05-04 02:34:21 -04:00
84e710da2a
We'll need to verify that there's neither a hashed nor in-lookup dentry with desired parent/name before adding to in-lookup set. One possible solution would be to hold the parent's ->d_lock through both checks, but while the in-lookup set is relatively small at any time, dcache is not. And holding the parent's ->d_lock through something like __d_lookup_rcu() would suck too badly. So we leave the parent's ->d_lock alone, which means that we watch out for the following scenario: * we verify that there's no hashed match * existing in-lookup match gets hashed by another process * we verify that there's no in-lookup matches and decide that everything's fine. Solution: per-directory kinda-sorta seqlock, bumped around the times we hash something that used to be in-lookup or move (and hash) something in place of in-lookup. Then the above would turn into * read the counter * do dcache lookup * if no matches found, check for in-lookup matches * if there had been none of those either, check if the counter has changed; repeat if it has. The "kinda-sorta" part is due to the fact that we don't have much spare space in inode. There is a spare word (shared with i_bdev/i_cdev/i_pipe), so the counter part is not a problem, but spinlock is a different story. We could use the parent's ->d_lock, and it would be less painful in terms of contention, for __d_add() it would be rather inconvenient to grab; we could do that (using lock_parent()), but... Fortunately, we can get serialization on the counter itself, and it might be a good idea in general; we can use cmpxchg() in a loop to get from even to odd and smp_store_release() from odd to even. This commit adds the counter and updating logics; the readers will be added in the next commit. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
||
|---|---|---|
| .. | ||
| caching | ||
| cifs | ||
| configfs | ||
| nfs | ||
| pohmelfs | ||
| .gitignore | ||
| 00-INDEX | ||
| 9p.txt | ||
| adfs.txt | ||
| affs.txt | ||
| afs.txt | ||
| autofs4-mount-control.txt | ||
| autofs4.txt | ||
| automount-support.txt | ||
| befs.txt | ||
| bfs.txt | ||
| btrfs.txt | ||
| ceph.txt | ||
| coda.txt | ||
| cramfs.txt | ||
| dax.txt | ||
| debugfs.txt | ||
| devpts.txt | ||
| directory-locking | ||
| dlmfs.txt | ||
| dnotify.txt | ||
| dnotify_test.c | ||
| ecryptfs.txt | ||
| efivarfs.txt | ||
| exofs.txt | ||
| ext2.txt | ||
| ext3.txt | ||
| ext4.txt | ||
| f2fs.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-online-filecheck.txt | ||
| ocfs2.txt | ||
| omfs.txt | ||
| orangefs.txt | ||
| overlayfs.txt | ||
| path-lookup.md | ||
| path-lookup.txt | ||
| porting | ||
| proc.txt | ||
| qnx6.txt | ||
| quota.txt | ||
| ramfs-rootfs-initramfs.txt | ||
| relay.txt | ||
| romfs.txt | ||
| seq_file.txt | ||
| sharedsubtree.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-self-describing-metadata.txt | ||
| xfs.txt | ||