fa0726854c
This patch fixed a race between ext3_discard_reservation() and ext3_try_to_allocate_with_rsv(). There is a window where ext3_discard_reservation will remove an already unlinked reservation window node from the filesystem reservation tree: It thinks the reservation is still linked in the filesystem reservation tree, but it is actually temperately removed from the tree by allocate_new_reservation() when it failed to make a new reservation from the current group and try to make a new reservation from next block group. Here is how it could happen: CPU 1 try to allocate a block in group1 with given reservation window my_rsv ext3_try_to_allocate_with_rsv(group ----copy reservation window my_rsv into local rsv_copy ext3_try_to_allocate(...rsv_copy) ----no free block in existing reservation window, ----need a new reservation window spin_lock(&rsv_lock); CPU 2 ext3_discard_reservation if (!rsv_is_empty() ----this is true spin_lock(&rsv_lock) ----waiting for thread 1 CPU 1: allocate_new_reservation failed to reserve blocks in this group remove the window from the tree rsv_window_remove(my_rsv) ----window node is unlinked from the tree here return -1 spin_unlock(&rsv_lock) ext3_try_to_allocate_with_rsv() failed in this group group++ CPU 2 spin_lock(&rsv_lock) succeed rsv_remove_window () ---------------break, trying to remove a unlinked node from the tree .... CPU 1: ext3_try_to_allocate_with_rsv(group, my_rsv) rsv_is_empty is true, need a new reservation window spin_lock(&rsv_lock); ^--------------- spinning forever We need to re-check whether the reservation window is still linked to the tree after grab the rsv_lock spin lock in ext3_discard_reservation, to prevent panic in rsv_remove_window->rb_erase. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Chris Wright <chrisw@osdl.org> |
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| .. | ||
| Makefile | ||
| acl.c | ||
| acl.h | ||
| balloc.c | ||
| bitmap.c | ||
| dir.c | ||
| file.c | ||
| fsync.c | ||
| hash.c | ||
| ialloc.c | ||
| inode.c | ||
| ioctl.c | ||
| namei.c | ||
| resize.c | ||
| super.c | ||
| symlink.c | ||
| xattr.c | ||
| xattr.h | ||
| xattr_security.c | ||
| xattr_trusted.c | ||
| xattr_user.c | ||