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2105c2820d
AFS directories are retained locally as a structured file, with lookup
being effected by a local search of the file contents. When a modification
(such as mkdir) happens, the dir file content is modified locally rather
than redownloading the directory.
The directory contents are accessed in a number of ways, with a number of
different locks schemes:
(1) Download of contents - dvnode->validate_lock/write in afs_read_dir().
(2) Lookup and readdir - dvnode->validate_lock/read in afs_dir_iterate(),
downgrading from (1) if necessary.
(3) d_revalidate of child dentry - dvnode->validate_lock/read in
afs_do_lookup_one() downgrading from (1) if necessary.
(4) Edit of dir after modification - page locks on individual dir pages.
Unfortunately, because (4) uses different locking scheme to (1) - (3),
nothing protects against the page being scanned whilst the edit is
underway. Even download is not safe as it doesn't lock the pages - relying
instead on the validate_lock to serialise as a whole (the theory being that
directory contents are treated as a block and always downloaded as a
block).
Fix this by write-locking dvnode->validate_lock around the edits. Care
must be taken in the rename case as there may be two different dirs - but
they need not be locked at the same time. In any case, once the lock is
taken, the directory version must be rechecked, and the edit skipped if a
later version has been downloaded by revalidation (there can't have been
any local changes because the VFS holds the inode lock, but there can have
been remote changes).
Fixes:
|
||
|---|---|---|
| .. | ||
| addr_list.c | ||
| afs_cm.h | ||
| afs_fs.h | ||
| afs_vl.h | ||
| afs.h | ||
| cache.c | ||
| callback.c | ||
| cell.c | ||
| cmservice.c | ||
| dir_edit.c | ||
| dir_silly.c | ||
| dir.c | ||
| dynroot.c | ||
| file.c | ||
| flock.c | ||
| fs_probe.c | ||
| fsclient.c | ||
| inode.c | ||
| internal.h | ||
| Kconfig | ||
| main.c | ||
| Makefile | ||
| misc.c | ||
| mntpt.c | ||
| proc.c | ||
| protocol_uae.h | ||
| protocol_yfs.h | ||
| rotate.c | ||
| rxrpc.c | ||
| security.c | ||
| server_list.c | ||
| server.c | ||
| super.c | ||
| vl_list.c | ||
| vl_probe.c | ||
| vl_rotate.c | ||
| vlclient.c | ||
| volume.c | ||
| write.c | ||
| xattr.c | ||
| xdr_fs.h | ||
| yfsclient.c | ||