scst_vdisk: Add zero-copy file I/O readsupport

Speeds up reading from a RAM disk via ib_srpt by about 30%.
Tested with iSCSI-SCST, ib_srpt and scst_local.

Signed-off-by: Bart Van Assche <[email protected]>

In it:

- Fixed NULLIO, which the original patch breaks

- Changed on all fast paths sBUG_ON() on EXTRACHECKS_BUG_ON()

- Fixed errors path in non_fileio_exec() and fileio_alloc_data_buf().

- Renamed zero_copy_read to just zero_copy.

- Docs and change log updated

- Some cleanups

iscsi-scst/ChangeLog

@@ -1,7 +1,7 @@
 Summary of changes between versions 2.1.0 and 3.0
 -------------------------------------------------
 
- - Update to kernels up to 3.1
+ - Update to kernels up to 3.3
 
  - Bug fixes and other improvements
 

qla2x00t/qla2x00-target/ChangeLog

@@ -1,7 +1,7 @@
 Summary of changes between versions 2.1.0 and 3.0
 -------------------------------------------------
 
- - Update to kernels up to 3.1
+ - Update to kernels up to 3.3
 
  - Bug fixes and other improvements
 

scst/ChangeLog

@@ -1,7 +1,9 @@
 Summary of changes between versions 2.1.0 and 3.0
 -------------------------------------------------
 
- - Update to kernels up to 3.1
+ - Update to kernels up to 3.3
+
+ - Zero copy read side FILEIO implemented
 
  - New initialization scripts implemented
 

scst/README

@@ -886,6 +886,9 @@ cache. The following parameters possible for vdisk_fileio:
  - rotational - if set, this device reported as rotational. Otherwise,
    it is reported as non-rotational (SSD, etc.)
 
+ - zero_copy - if set, then this device uses zero copy access to the
+   page cache. At the moment, only read side zero copy is implemented.
+
 Handler vdisk_blockio provides BLOCKIO mode to create virtual devices.
 This mode performs direct block I/O with a block device, bypassing the
 page cache for all operations. This mode works ideally with high-end

scst/README_in-tree

@@ -750,6 +750,9 @@ cache. The following parameters possible for vdisk_fileio:
  - rotational - if set, this device reported as rotational. Otherwise,
    it is reported as non-rotational (SSD, etc.)
 
+ - zero_copy - if set, then this device uses zero copy access to the
+   page cache. At the moment, only read side zero copy is implemented.
+
 Handler vdisk_blockio provides BLOCKIO mode to create virtual devices.
 This mode performs direct block I/O with a block device, bypassing the
 page cache for all operations. This mode works ideally with high-end

scst/include/scst.h

@@ -2420,18 +2420,6 @@ struct scst_device {
 #endif
 };
 
-/*
- * Used to store threads local tgt_dev specific data
- */
-struct scst_thr_data_hdr {
-	/* List entry in tgt_dev->thr_data_list */
-	struct list_head thr_data_list_entry;
-	struct task_struct *owner_thr; /* the owner thread */
-	atomic_t ref;
-	/* Function that will be called on the tgt_dev destruction */
-	void (*free_fn) (struct scst_thr_data_hdr *data);
-};
-
 /*
  * Used to clearly dispose async io_context
  */
@@ -2473,10 +2461,6 @@ struct scst_tgt_dev {
 	struct scst_order_data *curr_order_data;
 	struct scst_order_data tgt_dev_order_data;
 
-	/* List of scst_thr_data_hdr and lock */
-	spinlock_t thr_data_lock;
-	struct list_head thr_data_list;
-
 	/* Pointer to lists of commands with the lock */
 	struct scst_cmd_threads *active_cmd_threads;
 
@@ -3974,7 +3958,8 @@ static inline int scst_check_local_events(struct scst_cmd *cmd)
 	return __scst_check_local_events(cmd, true);
 }
 
-int scst_set_cmd_abnormal_done_state(struct scst_cmd *cmd);
+int scst_get_cmd_abnormal_done_state(const struct scst_cmd *cmd);
+void scst_set_cmd_abnormal_done_state(struct scst_cmd *cmd);
 
 struct scst_trace_log {
 	unsigned int val;
@@ -4129,34 +4114,6 @@ void scst_cmd_put(struct scst_cmd *cmd);
 struct scatterlist *scst_alloc(int size, gfp_t gfp_mask, int *count);
 void scst_free(struct scatterlist *sg, int count);
 
-void scst_add_thr_data(struct scst_tgt_dev *tgt_dev,
-	struct scst_thr_data_hdr *data,
-	void (*free_fn) (struct scst_thr_data_hdr *data));
-void scst_del_all_thr_data(struct scst_tgt_dev *tgt_dev);
-void scst_dev_del_all_thr_data(struct scst_device *dev);
-struct scst_thr_data_hdr *__scst_find_thr_data(struct scst_tgt_dev *tgt_dev,
-	struct task_struct *tsk);
-
-/* Finds local to the current thread data. Returns NULL, if they not found. */
-static inline struct scst_thr_data_hdr *scst_find_thr_data(
-	struct scst_tgt_dev *tgt_dev)
-{
-	return __scst_find_thr_data(tgt_dev, current);
-}
-
-/* Increase ref counter for the thread data */
-static inline void scst_thr_data_get(struct scst_thr_data_hdr *data)
-{
-	atomic_inc(&data->ref);
-}
-
-/* Decrease ref counter for the thread data */
-static inline void scst_thr_data_put(struct scst_thr_data_hdr *data)
-{
-	if (atomic_dec_and_test(&data->ref))
-		data->free_fn(data);
-}
-
 int scst_calc_block_shift(int sector_size);
 int scst_sbc_generic_parse(struct scst_cmd *cmd,
 	int (*get_block_shift)(struct scst_cmd *cmd));

scst/src/dev_handlers/scst_user.c

@@ -677,7 +677,7 @@ static int dev_user_alloc_space(struct scst_user_cmd *ucmd)
 		goto out;
 	else if (rc < 0) {
 		scst_set_busy(cmd);
-		res = scst_set_cmd_abnormal_done_state(cmd);
+		res = scst_get_cmd_abnormal_done_state(cmd);
 		goto out;
 	}
 
@@ -860,7 +860,7 @@ static int dev_user_parse(struct scst_cmd *cmd)
 	scst_set_cmd_error(cmd, SCST_LOAD_SENSE(scst_sense_invalid_opcode));
 
 out_error:
-	res = scst_set_cmd_abnormal_done_state(cmd);
+	res = scst_get_cmd_abnormal_done_state(cmd);
 	goto out;
 }