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/** |
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* This file is part of the CernVM File System. |
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*/ |
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#ifndef CVMFS_FUSE_REMOUNT_H_ |
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#define CVMFS_FUSE_REMOUNT_H_ |
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#include <pthread.h> |
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#include <ctime> |
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#include "crypto/hash.h" |
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#include "duplex_fuse.h" |
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#include "fence.h" |
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#include "fuse_evict.h" |
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#include "util/atomic.h" |
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#include "util/single_copy.h" |
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namespace cvmfs { |
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struct InodeGenerationInfo; |
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} |
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class MountPoint; |
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/** |
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* Orchestrates an orderly remount of a new snapshot revision in the Fuse |
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* module. Remounting always happens as a result of calling Check() followed |
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* by a call to TryFinish(). The Check() method is either called from the |
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* remount trigger or from the TalkManager. The TryFinish() method is either |
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* called from a fuse callback function or from CheckSynchronously(). If a new |
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* root file catalog is available online and the kernel caches got flushed, the |
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* actual heavy-lifting of applying the new catalog takes place in TryFinish(); |
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* |
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* Remounting is inherently asynchronous because the kernel caches need to be |
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* flushed. We do this through the FuseInvalidator. Once the FuseInvalidor |
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* is ready (either by waiting or by active eviction), we flush all user-level |
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* caches and reload a new root catalog. |
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*/ |
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class FuseRemounter : SingleCopy { |
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public: |
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enum Status { |
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kStatusUp2Date = 0, |
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kStatusDraining, |
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kStatusMaintenance, |
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kStatusFailGeneral, |
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kStatusFailNoSpace, |
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}; |
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FuseRemounter(MountPoint *mountpoint, |
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cvmfs::InodeGenerationInfo *inode_generation_info, |
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void **fuse_channel_or_session, |
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bool fuse_notify_invalidation); |
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~FuseRemounter(); |
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void Spawn(); |
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Status Check(); |
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Status CheckSynchronously(); |
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Status ChangeRoot(const shash::Any &root_hash); |
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void TryFinish(const shash::Any &root_hash = shash::Any()); |
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void EnterMaintenanceMode(); |
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bool IsCaching() { |
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return (atomic_read32(&maintenance_mode_) == 0) |
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&& (atomic_read32(&drainout_mode_) == 0); |
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} |
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bool IsInDrainoutMode() { return atomic_read32(&drainout_mode_) == 2; } |
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bool IsInMaintenanceMode() { return atomic_read32(&maintenance_mode_) == 1; } |
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Fence *fence() { return fence_; } |
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time_t catalogs_valid_until() { return catalogs_valid_until_; } |
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void InvalidateDentry(uint64_t parent_ino, const NameString &name) { |
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invalidator_->InvalidateDentry(parent_ino, name); |
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} |
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private: |
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static void *MainRemountTrigger(void *data); |
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bool HasRemountTrigger() { return pipe_remount_trigger_[0] >= 0; } |
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void SetAlarm(int timeout); |
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bool EnterCriticalSection() { return atomic_cas32(&critical_section_, 0, 1); } |
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void LeaveCriticalSection() { atomic_dec32(&critical_section_); /* 1 -> 0 */ } |
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void SetOfflineMode(bool value); |
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MountPoint *mountpoint_; ///< Not owned |
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cvmfs::InodeGenerationInfo *inode_generation_info_; ///< Not owned |
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FuseInvalidator *invalidator_; |
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/** |
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* Used to query whether the kernel cache invalidation is done. |
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*/ |
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FuseInvalidator::Handle invalidator_handle_; |
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/** |
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* Ensures that within a fuse callback all operations take place on the same |
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* catalog revision. |
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*/ |
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Fence *fence_; |
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/** |
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* This fence makes sure that Check() and TryFinish() have been left after |
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* the maintenance mode flag was set. |
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*/ |
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Fence fence_maintenance_; |
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pthread_t thread_remount_trigger_; |
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/** |
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* The thread that triggers the reload of the root catalog is controlled |
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* through this pipe. |
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*/ |
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int pipe_remount_trigger_[2]; |
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/** |
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* Indicates whether the last reload attempt failed. If so, the short term |
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* TTL is active. |
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*/ |
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bool offline_mode_; |
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/** |
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* Stores the deadline after which the remount trigger will look again for |
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* an updated version. Can be MountPoint::kIndefiniteDeadline if a fixed root |
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* catalog is used. Only for information purposes ('expires' xattr). |
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* TODO(jblomer): access to this field should be locked |
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*/ |
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time_t catalogs_valid_until_; |
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/** |
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* In drainout mode, the fuse module sets the timeout of meta data replies to |
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* zero. If supported by Fuse, the FuseInvalidator will evict all active |
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* entries from the kernel cache. Drainout mode is left only once the new |
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* root catalog is active (after TryFinish()). |
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* |
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* Moving into drainout mode is a two-steps procedure. Going from zero to one |
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* the handle of the FuseInvalidator is prepared, from one to two is the |
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* actual move into drainout mode. |
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*/ |
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atomic_int32 drainout_mode_; |
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/** |
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* in maintenance mode, cache timeout is 0 and catalogs are not reloaded. |
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* Maintenance mode is entered when the fuse module gets reloaded. |
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*/ |
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atomic_int32 maintenance_mode_; |
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/** |
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* Only one thread must perform the actual remount (stopping user-level |
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* caches, loading new catalog, etc.). This is used to protect TyrFinish() |
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* from concurrent execution. |
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*/ |
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atomic_int32 critical_section_; |
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}; // class FuseRemounter |
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#endif // CVMFS_FUSE_REMOUNT_H_ |
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