Hello, This is v3 of kernfs self-removal patchset. v2 posting mistakenly sent out slightly old set of patches, so the v3. Sorry about the noise. Changes from the first take[L] are,
* Patches reordered so that more trivial ones are in the front. * Deactivation split into a separate stage instead of being part of unlinking. Deactivation is now exposed as kernfs API via four new functions - kernfs_{de|re}activate[_self](). These functions can nest and allow implementation of "deactivate, lock subsys, try removal, unlock subsys, reactivate" sequence where removal may or may not succeed. This will be used to convert cgroup to kernfs. (prototype seems happy with this API) * As this means that deactivation can be temporary, kernfs_get_active() is updated to block if the node is deactivated but not removed. * kernfs_remove_self() is now implemented using the new deactivation API. Its behavior remains the same. Original patch description follows. kernfs / sysfs implement the "sever" semantic for userland accesses. When a node is removed, no further userland operations are allowed and the in-flight ones are drained before removal is finished. This makes policing post-mortem userland accesses trivial for its users; unfortunately, this comes with a drawback - a node which tries to delete oneself through one of its userland operations deadlocks. Removal wants to drain the active access that the operation itself is running on top of. This currently is worked around in the sysfs layer using sysfs_schedule_callback() which punts the actual removal to a work item. While making the operation asynchronous kinda works, it's a bit cumbersome to use and its behavior isn't quite correct as the caller has no way of telling when or even whether the operation is actually complete. If such self-removal is followed by another operation which expects the removed name to be available, there's no way to make the second operation reliable - e.g. something like "echo 1 > asdf/delete; echo asdf > create_new_child" can't work properly. This patchset improves kernfs removal path and implements kernfs_remove_self() which is to be called from an on-going kernfs operation and removes the self node. The function can be called concurrently and only one will return %true and all others will wait until the winner's file operation is complete (not the kernfs_remove_self() call itself but the enclosing file operation which invoked the function). This ensures that if there are multiple concurrent "echo 1 > asdf/delete", all of them would finish only after the whole store_delete() method is complete. kernfs_remove_self() is exposed to upper layers through sysfs_remove_file_self() and device_remove_file_self(). The existing users of device_schedule_callback() are converted to use remove_self and the unused async mechanism is removed. This patchset contains the following 14 patches. 0001-kernfs-fix-get_active-failure-handling-in-kernfs_seq.patch 0002-kernfs-replace-kernfs_node-u.completion-with-kernfs_.patch 0003-kernfs-remove-KERNFS_ACTIVE_REF-and-add-kernfs_lockd.patch 0004-kernfs-remove-KERNFS_REMOVED.patch 0005-kernfs-restructure-removal-path-to-fix-possible-prem.patch 0006-kernfs-invoke-kernfs_unmap_bin_file-directly-from-__.patch 0007-kernfs-remove-kernfs_addrm_cxt.patch 0008-kernfs-make-kernfs_get_active-block-if-the-node-is-d.patch 0009-kernfs-implement-kernfs_-de-re-activate-_self.patch 0010-kernfs-sysfs-driver-core-implement-kernfs_remove_sel.patch 0011-pci-use-device_remove_file_self-instead-of-device_sc.patch 0012-scsi-use-device_remove_file_self-instead-of-device_s.patch 0013-s390-use-device_remove_file_self-instead-of-device_s.patch 0014-sysfs-driver-core-remove-unused-sysfs-device-_schedu.patch 0001 fixes -ENODEV failure handling in kernfs. I *think* this could be the fix for the issue Sasha reported with trinity fuzzying. Sasha, would it be possible to confirm whether the issue is reproducible with this patch applied? 0002 replaces kernfs_node->u.completion with a hierarchy-wide wait_queue_head. This will be used to fix concurrent removal behavior. 0003-0004 simplifies removal path to prepare for restructuring. 0005 fixes premature completion of node removal when multiple removers are competing. This shouldn't matter for the existing sysfs users. 0006-0007 cleans up removal path. The size of kernfs_node gets reduced by one pointer. 0008-0010 implement kernfs_{de|re}activate[_self](), kernfs_remove_self() and friends. 0011-0014 convert the existing users of device_schedule_callback() to device_remove_file_self() and remove now unused async mechanism. After the changes, kernfs_node is shrunken by a pointer. Unfortunately, the addition of deactivation API makes LOC go up by above a hundred lines. Oh well.... The patchset is on top of the current driver-core-next eb4c69033fd1 ("Revert "kobject: introduce kobj_completion"") and also available in the following git branch. git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git review-kernfs-suicide diffstat follows. arch/s390/include/asm/ccwgroup.h | 1 arch/s390/pci/pci_sysfs.c | 18 - drivers/base/core.c | 50 +-- drivers/pci/pci-sysfs.c | 24 - drivers/s390/block/dcssblk.c | 14 drivers/s390/cio/ccwgroup.c | 26 + drivers/scsi/scsi_sysfs.c | 15 - fs/kernfs/dir.c | 585 ++++++++++++++++++++++++++------------- fs/kernfs/file.c | 62 +++- fs/kernfs/kernfs-internal.h | 17 - fs/kernfs/symlink.c | 6 fs/sysfs/file.c | 115 +------ include/linux/device.h | 13 include/linux/kernfs.h | 24 + include/linux/sysfs.h | 16 - 15 files changed, 555 insertions(+), 431 deletions(-) Thanks. -- tejun [L] git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git review-kernfs-suicide -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/