Revision 020ac5b6bef15785f9dde9de89d2734ff97da733 authored by Artem Bityutskiy on 31 May 2012, 23:26:12 UTC, committed by Linus Torvalds on 01 June 2012, 00:49:27 UTC
This is patchset makes fatfs stop using the VFS '->write_super()' method for writing out the FSINFO block. The final goal is to get rid of the 'sync_supers()' kernel thread. This kernel thread wakes up every 5 seconds (by default) and calls '->write_super()' for all mounted file-systems. And the bad thing is that this is done even if all the superblocks are clean. Moreover, some file-systems do not even need this end they do not register the '->write_super()' method at all (e.g., btrfs). So 'sync_supers()' most often just generates useless wake-ups and wastes power. I am trying to make all file-systems independent of '->write_super()' and plan to remove 'sync_supers()' and '->write_super' completely once there are no more users. The '->write_supers()' method is mostly used by baroque file-systems like hfs, udf, etc. Modern file-systems like btrfs and xfs do not use it. This justifies removing this stuff from VFS completely and make every FS self-manage own superblock. Tested with xfstests. This patch: Preparation for further changes. It introduces a special inode ('fsinfo_inode') in FAT file-system which we'll later use for managing the FSINFO block. Note, this there is already one special inode ('fat_inode') which is used for managing the FAT tables. Introduce new 'MSDOS_FSINFO_INO' constant for this special inode. It is safe to do because FAT file-system does not store inode numbers on the media but generates them run-time. I've also cleaned up the comment to existing 'MSDOS_ROOT_INO' constant, while on it. Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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iso-resources.c
/*
* isochronous resources helper functions
*
* Copyright (c) Clemens Ladisch <clemens@ladisch.de>
* Licensed under the terms of the GNU General Public License, version 2.
*/
#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/export.h>
#include <linux/jiffies.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include "iso-resources.h"
/**
* fw_iso_resources_init - initializes a &struct fw_iso_resources
* @r: the resource manager to initialize
* @unit: the device unit for which the resources will be needed
*
* If the device does not support all channel numbers, change @r->channels_mask
* after calling this function.
*/
int fw_iso_resources_init(struct fw_iso_resources *r, struct fw_unit *unit)
{
r->channels_mask = ~0uLL;
r->unit = fw_unit_get(unit);
mutex_init(&r->mutex);
r->allocated = false;
return 0;
}
EXPORT_SYMBOL(fw_iso_resources_init);
/**
* fw_iso_resources_destroy - destroy a resource manager
* @r: the resource manager that is no longer needed
*/
void fw_iso_resources_destroy(struct fw_iso_resources *r)
{
WARN_ON(r->allocated);
mutex_destroy(&r->mutex);
fw_unit_put(r->unit);
}
EXPORT_SYMBOL(fw_iso_resources_destroy);
static unsigned int packet_bandwidth(unsigned int max_payload_bytes, int speed)
{
unsigned int bytes, s400_bytes;
/* iso packets have three header quadlets and quadlet-aligned payload */
bytes = 3 * 4 + ALIGN(max_payload_bytes, 4);
/* convert to bandwidth units (quadlets at S1600 = bytes at S400) */
if (speed <= SCODE_400)
s400_bytes = bytes * (1 << (SCODE_400 - speed));
else
s400_bytes = DIV_ROUND_UP(bytes, 1 << (speed - SCODE_400));
return s400_bytes;
}
static int current_bandwidth_overhead(struct fw_card *card)
{
/*
* Under the usual pessimistic assumption (cable length 4.5 m), the
* isochronous overhead for N cables is 1.797 µs + N * 0.494 µs, or
* 88.3 + N * 24.3 in bandwidth units.
*
* The calculation below tries to deduce N from the current gap count.
* If the gap count has been optimized by measuring the actual packet
* transmission time, this derived overhead should be near the actual
* overhead as well.
*/
return card->gap_count < 63 ? card->gap_count * 97 / 10 + 89 : 512;
}
static int wait_isoch_resource_delay_after_bus_reset(struct fw_card *card)
{
for (;;) {
s64 delay = (card->reset_jiffies + HZ) - get_jiffies_64();
if (delay <= 0)
return 0;
if (schedule_timeout_interruptible(delay) > 0)
return -ERESTARTSYS;
}
}
/**
* fw_iso_resources_allocate - allocate isochronous channel and bandwidth
* @r: the resource manager
* @max_payload_bytes: the amount of data (including CIP headers) per packet
* @speed: the speed (e.g., SCODE_400) at which the packets will be sent
*
* This function allocates one isochronous channel and enough bandwidth for the
* specified packet size.
*
* Returns the channel number that the caller must use for streaming, or
* a negative error code. Due to potentionally long delays, this function is
* interruptible and can return -ERESTARTSYS. On success, the caller is
* responsible for calling fw_iso_resources_update() on bus resets, and
* fw_iso_resources_free() when the resources are not longer needed.
*/
int fw_iso_resources_allocate(struct fw_iso_resources *r,
unsigned int max_payload_bytes, int speed)
{
struct fw_card *card = fw_parent_device(r->unit)->card;
int bandwidth, channel, err;
if (WARN_ON(r->allocated))
return -EBADFD;
r->bandwidth = packet_bandwidth(max_payload_bytes, speed);
retry_after_bus_reset:
spin_lock_irq(&card->lock);
r->generation = card->generation;
r->bandwidth_overhead = current_bandwidth_overhead(card);
spin_unlock_irq(&card->lock);
err = wait_isoch_resource_delay_after_bus_reset(card);
if (err < 0)
return err;
mutex_lock(&r->mutex);
bandwidth = r->bandwidth + r->bandwidth_overhead;
fw_iso_resource_manage(card, r->generation, r->channels_mask,
&channel, &bandwidth, true);
if (channel == -EAGAIN) {
mutex_unlock(&r->mutex);
goto retry_after_bus_reset;
}
if (channel >= 0) {
r->channel = channel;
r->allocated = true;
} else {
if (channel == -EBUSY)
dev_err(&r->unit->device,
"isochronous resources exhausted\n");
else
dev_err(&r->unit->device,
"isochronous resource allocation failed\n");
}
mutex_unlock(&r->mutex);
return channel;
}
EXPORT_SYMBOL(fw_iso_resources_allocate);
/**
* fw_iso_resources_update - update resource allocations after a bus reset
* @r: the resource manager
*
* This function must be called from the driver's .update handler to reallocate
* any resources that were allocated before the bus reset. It is safe to call
* this function if no resources are currently allocated.
*
* Returns a negative error code on failure. If this happens, the caller must
* stop streaming.
*/
int fw_iso_resources_update(struct fw_iso_resources *r)
{
struct fw_card *card = fw_parent_device(r->unit)->card;
int bandwidth, channel;
mutex_lock(&r->mutex);
if (!r->allocated) {
mutex_unlock(&r->mutex);
return 0;
}
spin_lock_irq(&card->lock);
r->generation = card->generation;
r->bandwidth_overhead = current_bandwidth_overhead(card);
spin_unlock_irq(&card->lock);
bandwidth = r->bandwidth + r->bandwidth_overhead;
fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
&channel, &bandwidth, true);
/*
* When another bus reset happens, pretend that the allocation
* succeeded; we will try again for the new generation later.
*/
if (channel < 0 && channel != -EAGAIN) {
r->allocated = false;
if (channel == -EBUSY)
dev_err(&r->unit->device,
"isochronous resources exhausted\n");
else
dev_err(&r->unit->device,
"isochronous resource allocation failed\n");
}
mutex_unlock(&r->mutex);
return channel;
}
EXPORT_SYMBOL(fw_iso_resources_update);
/**
* fw_iso_resources_free - frees allocated resources
* @r: the resource manager
*
* This function deallocates the channel and bandwidth, if allocated.
*/
void fw_iso_resources_free(struct fw_iso_resources *r)
{
struct fw_card *card = fw_parent_device(r->unit)->card;
int bandwidth, channel;
mutex_lock(&r->mutex);
if (r->allocated) {
bandwidth = r->bandwidth + r->bandwidth_overhead;
fw_iso_resource_manage(card, r->generation, 1uLL << r->channel,
&channel, &bandwidth, false);
if (channel < 0)
dev_err(&r->unit->device,
"isochronous resource deallocation failed\n");
r->allocated = false;
}
mutex_unlock(&r->mutex);
}
EXPORT_SYMBOL(fw_iso_resources_free);
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