linux/fs/xfs/xfs_buf.c
Julia Lawall 89be677b6b xfs: xfs_buf: drop useless LIST_HEAD
Drop LIST_HEAD where the variable it declares has never
been used.

The semantic patch that fixes this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
identifier x;
@@
- LIST_HEAD(x);
  ... when != x
// </smpl>

Fixes: 26f1fe858f ("xfs: reduce lock hold times in buffer writeback")
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-12-29 10:47:34 -08:00

2197 lines
52 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2000-2006 Silicon Graphics, Inc.
* All Rights Reserved.
*/
#include "xfs.h"
#include <linux/stddef.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/vmalloc.h>
#include <linux/bio.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/workqueue.h>
#include <linux/percpu.h>
#include <linux/blkdev.h>
#include <linux/hash.h>
#include <linux/kthread.h>
#include <linux/migrate.h>
#include <linux/backing-dev.h>
#include <linux/freezer.h>
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_errortag.h"
#include "xfs_error.h"
static kmem_zone_t *xfs_buf_zone;
#define xb_to_gfp(flags) \
((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)
/*
* Locking orders
*
* xfs_buf_ioacct_inc:
* xfs_buf_ioacct_dec:
* b_sema (caller holds)
* b_lock
*
* xfs_buf_stale:
* b_sema (caller holds)
* b_lock
* lru_lock
*
* xfs_buf_rele:
* b_lock
* pag_buf_lock
* lru_lock
*
* xfs_buftarg_wait_rele
* lru_lock
* b_lock (trylock due to inversion)
*
* xfs_buftarg_isolate
* lru_lock
* b_lock (trylock due to inversion)
*/
static inline int
xfs_buf_is_vmapped(
struct xfs_buf *bp)
{
/*
* Return true if the buffer is vmapped.
*
* b_addr is null if the buffer is not mapped, but the code is clever
* enough to know it doesn't have to map a single page, so the check has
* to be both for b_addr and bp->b_page_count > 1.
*/
return bp->b_addr && bp->b_page_count > 1;
}
static inline int
xfs_buf_vmap_len(
struct xfs_buf *bp)
{
return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
}
/*
* Bump the I/O in flight count on the buftarg if we haven't yet done so for
* this buffer. The count is incremented once per buffer (per hold cycle)
* because the corresponding decrement is deferred to buffer release. Buffers
* can undergo I/O multiple times in a hold-release cycle and per buffer I/O
* tracking adds unnecessary overhead. This is used for sychronization purposes
* with unmount (see xfs_wait_buftarg()), so all we really need is a count of
* in-flight buffers.
*
* Buffers that are never released (e.g., superblock, iclog buffers) must set
* the XBF_NO_IOACCT flag before I/O submission. Otherwise, the buftarg count
* never reaches zero and unmount hangs indefinitely.
*/
static inline void
xfs_buf_ioacct_inc(
struct xfs_buf *bp)
{
if (bp->b_flags & XBF_NO_IOACCT)
return;
ASSERT(bp->b_flags & XBF_ASYNC);
spin_lock(&bp->b_lock);
if (!(bp->b_state & XFS_BSTATE_IN_FLIGHT)) {
bp->b_state |= XFS_BSTATE_IN_FLIGHT;
percpu_counter_inc(&bp->b_target->bt_io_count);
}
spin_unlock(&bp->b_lock);
}
/*
* Clear the in-flight state on a buffer about to be released to the LRU or
* freed and unaccount from the buftarg.
*/
static inline void
__xfs_buf_ioacct_dec(
struct xfs_buf *bp)
{
lockdep_assert_held(&bp->b_lock);
if (bp->b_state & XFS_BSTATE_IN_FLIGHT) {
bp->b_state &= ~XFS_BSTATE_IN_FLIGHT;
percpu_counter_dec(&bp->b_target->bt_io_count);
}
}
static inline void
xfs_buf_ioacct_dec(
struct xfs_buf *bp)
{
spin_lock(&bp->b_lock);
__xfs_buf_ioacct_dec(bp);
spin_unlock(&bp->b_lock);
}
/*
* When we mark a buffer stale, we remove the buffer from the LRU and clear the
* b_lru_ref count so that the buffer is freed immediately when the buffer
* reference count falls to zero. If the buffer is already on the LRU, we need
* to remove the reference that LRU holds on the buffer.
*
* This prevents build-up of stale buffers on the LRU.
*/
void
xfs_buf_stale(
struct xfs_buf *bp)
{
ASSERT(xfs_buf_islocked(bp));
bp->b_flags |= XBF_STALE;
/*
* Clear the delwri status so that a delwri queue walker will not
* flush this buffer to disk now that it is stale. The delwri queue has
* a reference to the buffer, so this is safe to do.
*/
bp->b_flags &= ~_XBF_DELWRI_Q;
/*
* Once the buffer is marked stale and unlocked, a subsequent lookup
* could reset b_flags. There is no guarantee that the buffer is
* unaccounted (released to LRU) before that occurs. Drop in-flight
* status now to preserve accounting consistency.
*/
spin_lock(&bp->b_lock);
__xfs_buf_ioacct_dec(bp);
atomic_set(&bp->b_lru_ref, 0);
if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
(list_lru_del(&bp->b_target->bt_lru, &bp->b_lru)))
atomic_dec(&bp->b_hold);
ASSERT(atomic_read(&bp->b_hold) >= 1);
spin_unlock(&bp->b_lock);
}
static int
xfs_buf_get_maps(
struct xfs_buf *bp,
int map_count)
{
ASSERT(bp->b_maps == NULL);
bp->b_map_count = map_count;
if (map_count == 1) {
bp->b_maps = &bp->__b_map;
return 0;
}
bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
KM_NOFS);
if (!bp->b_maps)
return -ENOMEM;
return 0;
}
/*
* Frees b_pages if it was allocated.
*/
static void
xfs_buf_free_maps(
struct xfs_buf *bp)
{
if (bp->b_maps != &bp->__b_map) {
kmem_free(bp->b_maps);
bp->b_maps = NULL;
}
}
struct xfs_buf *
_xfs_buf_alloc(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags)
{
struct xfs_buf *bp;
int error;
int i;
bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
if (unlikely(!bp))
return NULL;
/*
* We don't want certain flags to appear in b_flags unless they are
* specifically set by later operations on the buffer.
*/
flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
atomic_set(&bp->b_hold, 1);
atomic_set(&bp->b_lru_ref, 1);
init_completion(&bp->b_iowait);
INIT_LIST_HEAD(&bp->b_lru);
INIT_LIST_HEAD(&bp->b_list);
INIT_LIST_HEAD(&bp->b_li_list);
sema_init(&bp->b_sema, 0); /* held, no waiters */
spin_lock_init(&bp->b_lock);
bp->b_target = target;
bp->b_flags = flags;
/*
* Set length and io_length to the same value initially.
* I/O routines should use io_length, which will be the same in
* most cases but may be reset (e.g. XFS recovery).
*/
error = xfs_buf_get_maps(bp, nmaps);
if (error) {
kmem_zone_free(xfs_buf_zone, bp);
return NULL;
}
bp->b_bn = map[0].bm_bn;
bp->b_length = 0;
for (i = 0; i < nmaps; i++) {
bp->b_maps[i].bm_bn = map[i].bm_bn;
bp->b_maps[i].bm_len = map[i].bm_len;
bp->b_length += map[i].bm_len;
}
bp->b_io_length = bp->b_length;
atomic_set(&bp->b_pin_count, 0);
init_waitqueue_head(&bp->b_waiters);
XFS_STATS_INC(target->bt_mount, xb_create);
trace_xfs_buf_init(bp, _RET_IP_);
return bp;
}
/*
* Allocate a page array capable of holding a specified number
* of pages, and point the page buf at it.
*/
STATIC int
_xfs_buf_get_pages(
xfs_buf_t *bp,
int page_count)
{
/* Make sure that we have a page list */
if (bp->b_pages == NULL) {
bp->b_page_count = page_count;
if (page_count <= XB_PAGES) {
bp->b_pages = bp->b_page_array;
} else {
bp->b_pages = kmem_alloc(sizeof(struct page *) *
page_count, KM_NOFS);
if (bp->b_pages == NULL)
return -ENOMEM;
}
memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
}
return 0;
}
/*
* Frees b_pages if it was allocated.
*/
STATIC void
_xfs_buf_free_pages(
xfs_buf_t *bp)
{
if (bp->b_pages != bp->b_page_array) {
kmem_free(bp->b_pages);
bp->b_pages = NULL;
}
}
/*
* Releases the specified buffer.
*
* The modification state of any associated pages is left unchanged.
* The buffer must not be on any hash - use xfs_buf_rele instead for
* hashed and refcounted buffers
*/
void
xfs_buf_free(
xfs_buf_t *bp)
{
trace_xfs_buf_free(bp, _RET_IP_);
ASSERT(list_empty(&bp->b_lru));
if (bp->b_flags & _XBF_PAGES) {
uint i;
if (xfs_buf_is_vmapped(bp))
vm_unmap_ram(bp->b_addr - bp->b_offset,
bp->b_page_count);
for (i = 0; i < bp->b_page_count; i++) {
struct page *page = bp->b_pages[i];
__free_page(page);
}
} else if (bp->b_flags & _XBF_KMEM)
kmem_free(bp->b_addr);
_xfs_buf_free_pages(bp);
xfs_buf_free_maps(bp);
kmem_zone_free(xfs_buf_zone, bp);
}
/*
* Allocates all the pages for buffer in question and builds it's page list.
*/
STATIC int
xfs_buf_allocate_memory(
xfs_buf_t *bp,
uint flags)
{
size_t size;
size_t nbytes, offset;
gfp_t gfp_mask = xb_to_gfp(flags);
unsigned short page_count, i;
xfs_off_t start, end;
int error;
/*
* for buffers that are contained within a single page, just allocate
* the memory from the heap - there's no need for the complexity of
* page arrays to keep allocation down to order 0.
*/
size = BBTOB(bp->b_length);
if (size < PAGE_SIZE) {
bp->b_addr = kmem_alloc(size, KM_NOFS);
if (!bp->b_addr) {
/* low memory - use alloc_page loop instead */
goto use_alloc_page;
}
if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
((unsigned long)bp->b_addr & PAGE_MASK)) {
/* b_addr spans two pages - use alloc_page instead */
kmem_free(bp->b_addr);
bp->b_addr = NULL;
goto use_alloc_page;
}
bp->b_offset = offset_in_page(bp->b_addr);
bp->b_pages = bp->b_page_array;
bp->b_pages[0] = virt_to_page(bp->b_addr);
bp->b_page_count = 1;
bp->b_flags |= _XBF_KMEM;
return 0;
}
use_alloc_page:
start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
>> PAGE_SHIFT;
page_count = end - start;
error = _xfs_buf_get_pages(bp, page_count);
if (unlikely(error))
return error;
offset = bp->b_offset;
bp->b_flags |= _XBF_PAGES;
for (i = 0; i < bp->b_page_count; i++) {
struct page *page;
uint retries = 0;
retry:
page = alloc_page(gfp_mask);
if (unlikely(page == NULL)) {
if (flags & XBF_READ_AHEAD) {
bp->b_page_count = i;
error = -ENOMEM;
goto out_free_pages;
}
/*
* This could deadlock.
*
* But until all the XFS lowlevel code is revamped to
* handle buffer allocation failures we can't do much.
*/
if (!(++retries % 100))
xfs_err(NULL,
"%s(%u) possible memory allocation deadlock in %s (mode:0x%x)",
current->comm, current->pid,
__func__, gfp_mask);
XFS_STATS_INC(bp->b_target->bt_mount, xb_page_retries);
congestion_wait(BLK_RW_ASYNC, HZ/50);
goto retry;
}
XFS_STATS_INC(bp->b_target->bt_mount, xb_page_found);
nbytes = min_t(size_t, size, PAGE_SIZE - offset);
size -= nbytes;
bp->b_pages[i] = page;
offset = 0;
}
return 0;
out_free_pages:
for (i = 0; i < bp->b_page_count; i++)
__free_page(bp->b_pages[i]);
bp->b_flags &= ~_XBF_PAGES;
return error;
}
/*
* Map buffer into kernel address-space if necessary.
*/
STATIC int
_xfs_buf_map_pages(
xfs_buf_t *bp,
uint flags)
{
ASSERT(bp->b_flags & _XBF_PAGES);
if (bp->b_page_count == 1) {
/* A single page buffer is always mappable */
bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
} else if (flags & XBF_UNMAPPED) {
bp->b_addr = NULL;
} else {
int retried = 0;
unsigned nofs_flag;
/*
* vm_map_ram() will allocate auxillary structures (e.g.
* pagetables) with GFP_KERNEL, yet we are likely to be under
* GFP_NOFS context here. Hence we need to tell memory reclaim
* that we are in such a context via PF_MEMALLOC_NOFS to prevent
* memory reclaim re-entering the filesystem here and
* potentially deadlocking.
*/
nofs_flag = memalloc_nofs_save();
do {
bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
-1, PAGE_KERNEL);
if (bp->b_addr)
break;
vm_unmap_aliases();
} while (retried++ <= 1);
memalloc_nofs_restore(nofs_flag);
if (!bp->b_addr)
return -ENOMEM;
bp->b_addr += bp->b_offset;
}
return 0;
}
/*
* Finding and Reading Buffers
*/
static int
_xfs_buf_obj_cmp(
struct rhashtable_compare_arg *arg,
const void *obj)
{
const struct xfs_buf_map *map = arg->key;
const struct xfs_buf *bp = obj;
/*
* The key hashing in the lookup path depends on the key being the
* first element of the compare_arg, make sure to assert this.
*/
BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
if (bp->b_bn != map->bm_bn)
return 1;
if (unlikely(bp->b_length != map->bm_len)) {
/*
* found a block number match. If the range doesn't
* match, the only way this is allowed is if the buffer
* in the cache is stale and the transaction that made
* it stale has not yet committed. i.e. we are
* reallocating a busy extent. Skip this buffer and
* continue searching for an exact match.
*/
ASSERT(bp->b_flags & XBF_STALE);
return 1;
}
return 0;
}
static const struct rhashtable_params xfs_buf_hash_params = {
.min_size = 32, /* empty AGs have minimal footprint */
.nelem_hint = 16,
.key_len = sizeof(xfs_daddr_t),
.key_offset = offsetof(struct xfs_buf, b_bn),
.head_offset = offsetof(struct xfs_buf, b_rhash_head),
.automatic_shrinking = true,
.obj_cmpfn = _xfs_buf_obj_cmp,
};
int
xfs_buf_hash_init(
struct xfs_perag *pag)
{
spin_lock_init(&pag->pag_buf_lock);
return rhashtable_init(&pag->pag_buf_hash, &xfs_buf_hash_params);
}
void
xfs_buf_hash_destroy(
struct xfs_perag *pag)
{
rhashtable_destroy(&pag->pag_buf_hash);
}
/*
* Look up a buffer in the buffer cache and return it referenced and locked
* in @found_bp.
*
* If @new_bp is supplied and we have a lookup miss, insert @new_bp into the
* cache.
*
* If XBF_TRYLOCK is set in @flags, only try to lock the buffer and return
* -EAGAIN if we fail to lock it.
*
* Return values are:
* -EFSCORRUPTED if have been supplied with an invalid address
* -EAGAIN on trylock failure
* -ENOENT if we fail to find a match and @new_bp was NULL
* 0, with @found_bp:
* - @new_bp if we inserted it into the cache
* - the buffer we found and locked.
*/
static int
xfs_buf_find(
struct xfs_buftarg *btp,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
struct xfs_buf *new_bp,
struct xfs_buf **found_bp)
{
struct xfs_perag *pag;
xfs_buf_t *bp;
struct xfs_buf_map cmap = { .bm_bn = map[0].bm_bn };
xfs_daddr_t eofs;
int i;
*found_bp = NULL;
for (i = 0; i < nmaps; i++)
cmap.bm_len += map[i].bm_len;
/* Check for IOs smaller than the sector size / not sector aligned */
ASSERT(!(BBTOB(cmap.bm_len) < btp->bt_meta_sectorsize));
ASSERT(!(BBTOB(cmap.bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
/*
* Corrupted block numbers can get through to here, unfortunately, so we
* have to check that the buffer falls within the filesystem bounds.
*/
eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
if (cmap.bm_bn < 0 || cmap.bm_bn >= eofs) {
xfs_alert(btp->bt_mount,
"%s: daddr 0x%llx out of range, EOFS 0x%llx",
__func__, cmap.bm_bn, eofs);
WARN_ON(1);
return -EFSCORRUPTED;
}
pag = xfs_perag_get(btp->bt_mount,
xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
spin_lock(&pag->pag_buf_lock);
bp = rhashtable_lookup_fast(&pag->pag_buf_hash, &cmap,
xfs_buf_hash_params);
if (bp) {
atomic_inc(&bp->b_hold);
goto found;
}
/* No match found */
if (!new_bp) {
XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
spin_unlock(&pag->pag_buf_lock);
xfs_perag_put(pag);
return -ENOENT;
}
/* the buffer keeps the perag reference until it is freed */
new_bp->b_pag = pag;
rhashtable_insert_fast(&pag->pag_buf_hash, &new_bp->b_rhash_head,
xfs_buf_hash_params);
spin_unlock(&pag->pag_buf_lock);
*found_bp = new_bp;
return 0;
found:
spin_unlock(&pag->pag_buf_lock);
xfs_perag_put(pag);
if (!xfs_buf_trylock(bp)) {
if (flags & XBF_TRYLOCK) {
xfs_buf_rele(bp);
XFS_STATS_INC(btp->bt_mount, xb_busy_locked);
return -EAGAIN;
}
xfs_buf_lock(bp);
XFS_STATS_INC(btp->bt_mount, xb_get_locked_waited);
}
/*
* if the buffer is stale, clear all the external state associated with
* it. We need to keep flags such as how we allocated the buffer memory
* intact here.
*/
if (bp->b_flags & XBF_STALE) {
ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
ASSERT(bp->b_iodone == NULL);
bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
bp->b_ops = NULL;
}
trace_xfs_buf_find(bp, flags, _RET_IP_);
XFS_STATS_INC(btp->bt_mount, xb_get_locked);
*found_bp = bp;
return 0;
}
struct xfs_buf *
xfs_buf_incore(
struct xfs_buftarg *target,
xfs_daddr_t blkno,
size_t numblks,
xfs_buf_flags_t flags)
{
struct xfs_buf *bp;
int error;
DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
error = xfs_buf_find(target, &map, 1, flags, NULL, &bp);
if (error)
return NULL;
return bp;
}
/*
* Assembles a buffer covering the specified range. The code is optimised for
* cache hits, as metadata intensive workloads will see 3 orders of magnitude
* more hits than misses.
*/
struct xfs_buf *
xfs_buf_get_map(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags)
{
struct xfs_buf *bp;
struct xfs_buf *new_bp;
int error = 0;
error = xfs_buf_find(target, map, nmaps, flags, NULL, &bp);
switch (error) {
case 0:
/* cache hit */
goto found;
case -EAGAIN:
/* cache hit, trylock failure, caller handles failure */
ASSERT(flags & XBF_TRYLOCK);
return NULL;
case -ENOENT:
/* cache miss, go for insert */
break;
case -EFSCORRUPTED:
default:
/*
* None of the higher layers understand failure types
* yet, so return NULL to signal a fatal lookup error.
*/
return NULL;
}
new_bp = _xfs_buf_alloc(target, map, nmaps, flags);
if (unlikely(!new_bp))
return NULL;
error = xfs_buf_allocate_memory(new_bp, flags);
if (error) {
xfs_buf_free(new_bp);
return NULL;
}
error = xfs_buf_find(target, map, nmaps, flags, new_bp, &bp);
if (error) {
xfs_buf_free(new_bp);
return NULL;
}
if (bp != new_bp)
xfs_buf_free(new_bp);
found:
if (!bp->b_addr) {
error = _xfs_buf_map_pages(bp, flags);
if (unlikely(error)) {
xfs_warn(target->bt_mount,
"%s: failed to map pagesn", __func__);
xfs_buf_relse(bp);
return NULL;
}
}
/*
* Clear b_error if this is a lookup from a caller that doesn't expect
* valid data to be found in the buffer.
*/
if (!(flags & XBF_READ))
xfs_buf_ioerror(bp, 0);
XFS_STATS_INC(target->bt_mount, xb_get);
trace_xfs_buf_get(bp, flags, _RET_IP_);
return bp;
}
STATIC int
_xfs_buf_read(
xfs_buf_t *bp,
xfs_buf_flags_t flags)
{
ASSERT(!(flags & XBF_WRITE));
ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
return xfs_buf_submit(bp);
}
/*
* If the caller passed in an ops structure and the buffer doesn't have ops
* assigned, set the ops and use them to verify the contents. If the contents
* cannot be verified, we'll clear XBF_DONE. We assume the buffer has no
* recorded errors and is already in XBF_DONE state.
*/
int
xfs_buf_ensure_ops(
struct xfs_buf *bp,
const struct xfs_buf_ops *ops)
{
ASSERT(bp->b_flags & XBF_DONE);
ASSERT(bp->b_error == 0);
if (!ops || bp->b_ops)
return 0;
bp->b_ops = ops;
bp->b_ops->verify_read(bp);
if (bp->b_error)
bp->b_flags &= ~XBF_DONE;
return bp->b_error;
}
xfs_buf_t *
xfs_buf_read_map(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
const struct xfs_buf_ops *ops)
{
struct xfs_buf *bp;
flags |= XBF_READ;
bp = xfs_buf_get_map(target, map, nmaps, flags);
if (!bp)
return NULL;
trace_xfs_buf_read(bp, flags, _RET_IP_);
if (!(bp->b_flags & XBF_DONE)) {
XFS_STATS_INC(target->bt_mount, xb_get_read);
bp->b_ops = ops;
_xfs_buf_read(bp, flags);
return bp;
}
xfs_buf_ensure_ops(bp, ops);
if (flags & XBF_ASYNC) {
/*
* Read ahead call which is already satisfied,
* drop the buffer
*/
xfs_buf_relse(bp);
return NULL;
}
/* We do not want read in the flags */
bp->b_flags &= ~XBF_READ;
ASSERT(bp->b_ops != NULL || ops == NULL);
return bp;
}
/*
* If we are not low on memory then do the readahead in a deadlock
* safe manner.
*/
void
xfs_buf_readahead_map(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
const struct xfs_buf_ops *ops)
{
if (bdi_read_congested(target->bt_bdev->bd_bdi))
return;
xfs_buf_read_map(target, map, nmaps,
XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD, ops);
}
/*
* Read an uncached buffer from disk. Allocates and returns a locked
* buffer containing the disk contents or nothing.
*/
int
xfs_buf_read_uncached(
struct xfs_buftarg *target,
xfs_daddr_t daddr,
size_t numblks,
int flags,
struct xfs_buf **bpp,
const struct xfs_buf_ops *ops)
{
struct xfs_buf *bp;
*bpp = NULL;
bp = xfs_buf_get_uncached(target, numblks, flags);
if (!bp)
return -ENOMEM;
/* set up the buffer for a read IO */
ASSERT(bp->b_map_count == 1);
bp->b_bn = XFS_BUF_DADDR_NULL; /* always null for uncached buffers */
bp->b_maps[0].bm_bn = daddr;
bp->b_flags |= XBF_READ;
bp->b_ops = ops;
xfs_buf_submit(bp);
if (bp->b_error) {
int error = bp->b_error;
xfs_buf_relse(bp);
return error;
}
*bpp = bp;
return 0;
}
/*
* Return a buffer allocated as an empty buffer and associated to external
* memory via xfs_buf_associate_memory() back to it's empty state.
*/
void
xfs_buf_set_empty(
struct xfs_buf *bp,
size_t numblks)
{
if (bp->b_pages)
_xfs_buf_free_pages(bp);
bp->b_pages = NULL;
bp->b_page_count = 0;
bp->b_addr = NULL;
bp->b_length = numblks;
bp->b_io_length = numblks;
ASSERT(bp->b_map_count == 1);
bp->b_bn = XFS_BUF_DADDR_NULL;
bp->b_maps[0].bm_bn = XFS_BUF_DADDR_NULL;
bp->b_maps[0].bm_len = bp->b_length;
}
static inline struct page *
mem_to_page(
void *addr)
{
if ((!is_vmalloc_addr(addr))) {
return virt_to_page(addr);
} else {
return vmalloc_to_page(addr);
}
}
int
xfs_buf_associate_memory(
xfs_buf_t *bp,
void *mem,
size_t len)
{
int rval;
int i = 0;
unsigned long pageaddr;
unsigned long offset;
size_t buflen;
int page_count;
pageaddr = (unsigned long)mem & PAGE_MASK;
offset = (unsigned long)mem - pageaddr;
buflen = PAGE_ALIGN(len + offset);
page_count = buflen >> PAGE_SHIFT;
/* Free any previous set of page pointers */
if (bp->b_pages)
_xfs_buf_free_pages(bp);
bp->b_pages = NULL;
bp->b_addr = mem;
rval = _xfs_buf_get_pages(bp, page_count);
if (rval)
return rval;
bp->b_offset = offset;
for (i = 0; i < bp->b_page_count; i++) {
bp->b_pages[i] = mem_to_page((void *)pageaddr);
pageaddr += PAGE_SIZE;
}
bp->b_io_length = BTOBB(len);
bp->b_length = BTOBB(buflen);
return 0;
}
xfs_buf_t *
xfs_buf_get_uncached(
struct xfs_buftarg *target,
size_t numblks,
int flags)
{
unsigned long page_count;
int error, i;
struct xfs_buf *bp;
DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
/* flags might contain irrelevant bits, pass only what we care about */
bp = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT);
if (unlikely(bp == NULL))
goto fail;
page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
error = _xfs_buf_get_pages(bp, page_count);
if (error)
goto fail_free_buf;
for (i = 0; i < page_count; i++) {
bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
if (!bp->b_pages[i])
goto fail_free_mem;
}
bp->b_flags |= _XBF_PAGES;
error = _xfs_buf_map_pages(bp, 0);
if (unlikely(error)) {
xfs_warn(target->bt_mount,
"%s: failed to map pages", __func__);
goto fail_free_mem;
}
trace_xfs_buf_get_uncached(bp, _RET_IP_);
return bp;
fail_free_mem:
while (--i >= 0)
__free_page(bp->b_pages[i]);
_xfs_buf_free_pages(bp);
fail_free_buf:
xfs_buf_free_maps(bp);
kmem_zone_free(xfs_buf_zone, bp);
fail:
return NULL;
}
/*
* Increment reference count on buffer, to hold the buffer concurrently
* with another thread which may release (free) the buffer asynchronously.
* Must hold the buffer already to call this function.
*/
void
xfs_buf_hold(
xfs_buf_t *bp)
{
trace_xfs_buf_hold(bp, _RET_IP_);
atomic_inc(&bp->b_hold);
}
/*
* Release a hold on the specified buffer. If the hold count is 1, the buffer is
* placed on LRU or freed (depending on b_lru_ref).
*/
void
xfs_buf_rele(
xfs_buf_t *bp)
{
struct xfs_perag *pag = bp->b_pag;
bool release;
bool freebuf = false;
trace_xfs_buf_rele(bp, _RET_IP_);
if (!pag) {
ASSERT(list_empty(&bp->b_lru));
if (atomic_dec_and_test(&bp->b_hold)) {
xfs_buf_ioacct_dec(bp);
xfs_buf_free(bp);
}
return;
}
ASSERT(atomic_read(&bp->b_hold) > 0);
/*
* We grab the b_lock here first to serialise racing xfs_buf_rele()
* calls. The pag_buf_lock being taken on the last reference only
* serialises against racing lookups in xfs_buf_find(). IOWs, the second
* to last reference we drop here is not serialised against the last
* reference until we take bp->b_lock. Hence if we don't grab b_lock
* first, the last "release" reference can win the race to the lock and
* free the buffer before the second-to-last reference is processed,
* leading to a use-after-free scenario.
*/
spin_lock(&bp->b_lock);
release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
if (!release) {
/*
* Drop the in-flight state if the buffer is already on the LRU
* and it holds the only reference. This is racy because we
* haven't acquired the pag lock, but the use of _XBF_IN_FLIGHT
* ensures the decrement occurs only once per-buf.
*/
if ((atomic_read(&bp->b_hold) == 1) && !list_empty(&bp->b_lru))
__xfs_buf_ioacct_dec(bp);
goto out_unlock;
}
/* the last reference has been dropped ... */
__xfs_buf_ioacct_dec(bp);
if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
/*
* If the buffer is added to the LRU take a new reference to the
* buffer for the LRU and clear the (now stale) dispose list
* state flag
*/
if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
bp->b_state &= ~XFS_BSTATE_DISPOSE;
atomic_inc(&bp->b_hold);
}
spin_unlock(&pag->pag_buf_lock);
} else {
/*
* most of the time buffers will already be removed from the
* LRU, so optimise that case by checking for the
* XFS_BSTATE_DISPOSE flag indicating the last list the buffer
* was on was the disposal list
*/
if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
} else {
ASSERT(list_empty(&bp->b_lru));
}
ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
rhashtable_remove_fast(&pag->pag_buf_hash, &bp->b_rhash_head,
xfs_buf_hash_params);
spin_unlock(&pag->pag_buf_lock);
xfs_perag_put(pag);
freebuf = true;
}
out_unlock:
spin_unlock(&bp->b_lock);
if (freebuf)
xfs_buf_free(bp);
}
/*
* Lock a buffer object, if it is not already locked.
*
* If we come across a stale, pinned, locked buffer, we know that we are
* being asked to lock a buffer that has been reallocated. Because it is
* pinned, we know that the log has not been pushed to disk and hence it
* will still be locked. Rather than continuing to have trylock attempts
* fail until someone else pushes the log, push it ourselves before
* returning. This means that the xfsaild will not get stuck trying
* to push on stale inode buffers.
*/
int
xfs_buf_trylock(
struct xfs_buf *bp)
{
int locked;
locked = down_trylock(&bp->b_sema) == 0;
if (locked)
trace_xfs_buf_trylock(bp, _RET_IP_);
else
trace_xfs_buf_trylock_fail(bp, _RET_IP_);
return locked;
}
/*
* Lock a buffer object.
*
* If we come across a stale, pinned, locked buffer, we know that we
* are being asked to lock a buffer that has been reallocated. Because
* it is pinned, we know that the log has not been pushed to disk and
* hence it will still be locked. Rather than sleeping until someone
* else pushes the log, push it ourselves before trying to get the lock.
*/
void
xfs_buf_lock(
struct xfs_buf *bp)
{
trace_xfs_buf_lock(bp, _RET_IP_);
if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
xfs_log_force(bp->b_target->bt_mount, 0);
down(&bp->b_sema);
trace_xfs_buf_lock_done(bp, _RET_IP_);
}
void
xfs_buf_unlock(
struct xfs_buf *bp)
{
ASSERT(xfs_buf_islocked(bp));
up(&bp->b_sema);
trace_xfs_buf_unlock(bp, _RET_IP_);
}
STATIC void
xfs_buf_wait_unpin(
xfs_buf_t *bp)
{
DECLARE_WAITQUEUE (wait, current);
if (atomic_read(&bp->b_pin_count) == 0)
return;
add_wait_queue(&bp->b_waiters, &wait);
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (atomic_read(&bp->b_pin_count) == 0)
break;
io_schedule();
}
remove_wait_queue(&bp->b_waiters, &wait);
set_current_state(TASK_RUNNING);
}
/*
* Buffer Utility Routines
*/
void
xfs_buf_ioend(
struct xfs_buf *bp)
{
bool read = bp->b_flags & XBF_READ;
trace_xfs_buf_iodone(bp, _RET_IP_);
bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
/*
* Pull in IO completion errors now. We are guaranteed to be running
* single threaded, so we don't need the lock to read b_io_error.
*/
if (!bp->b_error && bp->b_io_error)
xfs_buf_ioerror(bp, bp->b_io_error);
/* Only validate buffers that were read without errors */
if (read && !bp->b_error && bp->b_ops) {
ASSERT(!bp->b_iodone);
bp->b_ops->verify_read(bp);
}
if (!bp->b_error)
bp->b_flags |= XBF_DONE;
if (bp->b_iodone)
(*(bp->b_iodone))(bp);
else if (bp->b_flags & XBF_ASYNC)
xfs_buf_relse(bp);
else
complete(&bp->b_iowait);
}
static void
xfs_buf_ioend_work(
struct work_struct *work)
{
struct xfs_buf *bp =
container_of(work, xfs_buf_t, b_ioend_work);
xfs_buf_ioend(bp);
}
static void
xfs_buf_ioend_async(
struct xfs_buf *bp)
{
INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);
queue_work(bp->b_ioend_wq, &bp->b_ioend_work);
}
void
__xfs_buf_ioerror(
xfs_buf_t *bp,
int error,
xfs_failaddr_t failaddr)
{
ASSERT(error <= 0 && error >= -1000);
bp->b_error = error;
trace_xfs_buf_ioerror(bp, error, failaddr);
}
void
xfs_buf_ioerror_alert(
struct xfs_buf *bp,
const char *func)
{
xfs_alert(bp->b_target->bt_mount,
"metadata I/O error in \"%s\" at daddr 0x%llx len %d error %d",
func, (uint64_t)XFS_BUF_ADDR(bp), bp->b_length,
-bp->b_error);
}
int
xfs_bwrite(
struct xfs_buf *bp)
{
int error;
ASSERT(xfs_buf_islocked(bp));
bp->b_flags |= XBF_WRITE;
bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
XBF_WRITE_FAIL | XBF_DONE);
error = xfs_buf_submit(bp);
if (error) {
xfs_force_shutdown(bp->b_target->bt_mount,
SHUTDOWN_META_IO_ERROR);
}
return error;
}
static void
xfs_buf_bio_end_io(
struct bio *bio)
{
struct xfs_buf *bp = (struct xfs_buf *)bio->bi_private;
/*
* don't overwrite existing errors - otherwise we can lose errors on
* buffers that require multiple bios to complete.
*/
if (bio->bi_status) {
int error = blk_status_to_errno(bio->bi_status);
cmpxchg(&bp->b_io_error, 0, error);
}
if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
xfs_buf_ioend_async(bp);
bio_put(bio);
}
static void
xfs_buf_ioapply_map(
struct xfs_buf *bp,
int map,
int *buf_offset,
int *count,
int op,
int op_flags)
{
int page_index;
int total_nr_pages = bp->b_page_count;
int nr_pages;
struct bio *bio;
sector_t sector = bp->b_maps[map].bm_bn;
int size;
int offset;
/* skip the pages in the buffer before the start offset */
page_index = 0;
offset = *buf_offset;
while (offset >= PAGE_SIZE) {
page_index++;
offset -= PAGE_SIZE;
}
/*
* Limit the IO size to the length of the current vector, and update the
* remaining IO count for the next time around.
*/
size = min_t(int, BBTOB(bp->b_maps[map].bm_len), *count);
*count -= size;
*buf_offset += size;
next_chunk:
atomic_inc(&bp->b_io_remaining);
nr_pages = min(total_nr_pages, BIO_MAX_PAGES);
bio = bio_alloc(GFP_NOIO, nr_pages);
bio_set_dev(bio, bp->b_target->bt_bdev);
bio->bi_iter.bi_sector = sector;
bio->bi_end_io = xfs_buf_bio_end_io;
bio->bi_private = bp;
bio_set_op_attrs(bio, op, op_flags);
for (; size && nr_pages; nr_pages--, page_index++) {
int rbytes, nbytes = PAGE_SIZE - offset;
if (nbytes > size)
nbytes = size;
rbytes = bio_add_page(bio, bp->b_pages[page_index], nbytes,
offset);
if (rbytes < nbytes)
break;
offset = 0;
sector += BTOBB(nbytes);
size -= nbytes;
total_nr_pages--;
}
if (likely(bio->bi_iter.bi_size)) {
if (xfs_buf_is_vmapped(bp)) {
flush_kernel_vmap_range(bp->b_addr,
xfs_buf_vmap_len(bp));
}
submit_bio(bio);
if (size)
goto next_chunk;
} else {
/*
* This is guaranteed not to be the last io reference count
* because the caller (xfs_buf_submit) holds a count itself.
*/
atomic_dec(&bp->b_io_remaining);
xfs_buf_ioerror(bp, -EIO);
bio_put(bio);
}
}
STATIC void
_xfs_buf_ioapply(
struct xfs_buf *bp)
{
struct blk_plug plug;
int op;
int op_flags = 0;
int offset;
int size;
int i;
/*
* Make sure we capture only current IO errors rather than stale errors
* left over from previous use of the buffer (e.g. failed readahead).
*/
bp->b_error = 0;
/*
* Initialize the I/O completion workqueue if we haven't yet or the
* submitter has not opted to specify a custom one.
*/
if (!bp->b_ioend_wq)
bp->b_ioend_wq = bp->b_target->bt_mount->m_buf_workqueue;
if (bp->b_flags & XBF_WRITE) {
op = REQ_OP_WRITE;
if (bp->b_flags & XBF_SYNCIO)
op_flags = REQ_SYNC;
if (bp->b_flags & XBF_FUA)
op_flags |= REQ_FUA;
if (bp->b_flags & XBF_FLUSH)
op_flags |= REQ_PREFLUSH;
/*
* Run the write verifier callback function if it exists. If
* this function fails it will mark the buffer with an error and
* the IO should not be dispatched.
*/
if (bp->b_ops) {
bp->b_ops->verify_write(bp);
if (bp->b_error) {
xfs_force_shutdown(bp->b_target->bt_mount,
SHUTDOWN_CORRUPT_INCORE);
return;
}
} else if (bp->b_bn != XFS_BUF_DADDR_NULL) {
struct xfs_mount *mp = bp->b_target->bt_mount;
/*
* non-crc filesystems don't attach verifiers during
* log recovery, so don't warn for such filesystems.
*/
if (xfs_sb_version_hascrc(&mp->m_sb)) {
xfs_warn(mp,
"%s: no buf ops on daddr 0x%llx len %d",
__func__, bp->b_bn, bp->b_length);
xfs_hex_dump(bp->b_addr,
XFS_CORRUPTION_DUMP_LEN);
dump_stack();
}
}
} else if (bp->b_flags & XBF_READ_AHEAD) {
op = REQ_OP_READ;
op_flags = REQ_RAHEAD;
} else {
op = REQ_OP_READ;
}
/* we only use the buffer cache for meta-data */
op_flags |= REQ_META;
/*
* Walk all the vectors issuing IO on them. Set up the initial offset
* into the buffer and the desired IO size before we start -
* _xfs_buf_ioapply_vec() will modify them appropriately for each
* subsequent call.
*/
offset = bp->b_offset;
size = BBTOB(bp->b_io_length);
blk_start_plug(&plug);
for (i = 0; i < bp->b_map_count; i++) {
xfs_buf_ioapply_map(bp, i, &offset, &size, op, op_flags);
if (bp->b_error)
break;
if (size <= 0)
break; /* all done */
}
blk_finish_plug(&plug);
}
/*
* Wait for I/O completion of a sync buffer and return the I/O error code.
*/
static int
xfs_buf_iowait(
struct xfs_buf *bp)
{
ASSERT(!(bp->b_flags & XBF_ASYNC));
trace_xfs_buf_iowait(bp, _RET_IP_);
wait_for_completion(&bp->b_iowait);
trace_xfs_buf_iowait_done(bp, _RET_IP_);
return bp->b_error;
}
/*
* Buffer I/O submission path, read or write. Asynchronous submission transfers
* the buffer lock ownership and the current reference to the IO. It is not
* safe to reference the buffer after a call to this function unless the caller
* holds an additional reference itself.
*/
int
__xfs_buf_submit(
struct xfs_buf *bp,
bool wait)
{
int error = 0;
trace_xfs_buf_submit(bp, _RET_IP_);
ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
/* on shutdown we stale and complete the buffer immediately */
if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
xfs_buf_ioerror(bp, -EIO);
bp->b_flags &= ~XBF_DONE;
xfs_buf_stale(bp);
if (bp->b_flags & XBF_ASYNC)
xfs_buf_ioend(bp);
return -EIO;
}
/*
* Grab a reference so the buffer does not go away underneath us. For
* async buffers, I/O completion drops the callers reference, which
* could occur before submission returns.
*/
xfs_buf_hold(bp);
if (bp->b_flags & XBF_WRITE)
xfs_buf_wait_unpin(bp);
/* clear the internal error state to avoid spurious errors */
bp->b_io_error = 0;
/*
* Set the count to 1 initially, this will stop an I/O completion
* callout which happens before we have started all the I/O from calling
* xfs_buf_ioend too early.
*/
atomic_set(&bp->b_io_remaining, 1);
if (bp->b_flags & XBF_ASYNC)
xfs_buf_ioacct_inc(bp);
_xfs_buf_ioapply(bp);
/*
* If _xfs_buf_ioapply failed, we can get back here with only the IO
* reference we took above. If we drop it to zero, run completion so
* that we don't return to the caller with completion still pending.
*/
if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
xfs_buf_ioend(bp);
else
xfs_buf_ioend_async(bp);
}
if (wait)
error = xfs_buf_iowait(bp);
/*
* Release the hold that keeps the buffer referenced for the entire
* I/O. Note that if the buffer is async, it is not safe to reference
* after this release.
*/
xfs_buf_rele(bp);
return error;
}
void *
xfs_buf_offset(
struct xfs_buf *bp,
size_t offset)
{
struct page *page;
if (bp->b_addr)
return bp->b_addr + offset;
offset += bp->b_offset;
page = bp->b_pages[offset >> PAGE_SHIFT];
return page_address(page) + (offset & (PAGE_SIZE-1));
}
/*
* Move data into or out of a buffer.
*/
void
xfs_buf_iomove(
xfs_buf_t *bp, /* buffer to process */
size_t boff, /* starting buffer offset */
size_t bsize, /* length to copy */
void *data, /* data address */
xfs_buf_rw_t mode) /* read/write/zero flag */
{
size_t bend;
bend = boff + bsize;
while (boff < bend) {
struct page *page;
int page_index, page_offset, csize;
page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
page = bp->b_pages[page_index];
csize = min_t(size_t, PAGE_SIZE - page_offset,
BBTOB(bp->b_io_length) - boff);
ASSERT((csize + page_offset) <= PAGE_SIZE);
switch (mode) {
case XBRW_ZERO:
memset(page_address(page) + page_offset, 0, csize);
break;
case XBRW_READ:
memcpy(data, page_address(page) + page_offset, csize);
break;
case XBRW_WRITE:
memcpy(page_address(page) + page_offset, data, csize);
}
boff += csize;
data += csize;
}
}
/*
* Handling of buffer targets (buftargs).
*/
/*
* Wait for any bufs with callbacks that have been submitted but have not yet
* returned. These buffers will have an elevated hold count, so wait on those
* while freeing all the buffers only held by the LRU.
*/
static enum lru_status
xfs_buftarg_wait_rele(
struct list_head *item,
struct list_lru_one *lru,
spinlock_t *lru_lock,
void *arg)
{
struct xfs_buf *bp = container_of(item, struct xfs_buf, b_lru);
struct list_head *dispose = arg;
if (atomic_read(&bp->b_hold) > 1) {
/* need to wait, so skip it this pass */
trace_xfs_buf_wait_buftarg(bp, _RET_IP_);
return LRU_SKIP;
}
if (!spin_trylock(&bp->b_lock))
return LRU_SKIP;
/*
* clear the LRU reference count so the buffer doesn't get
* ignored in xfs_buf_rele().
*/
atomic_set(&bp->b_lru_ref, 0);
bp->b_state |= XFS_BSTATE_DISPOSE;
list_lru_isolate_move(lru, item, dispose);
spin_unlock(&bp->b_lock);
return LRU_REMOVED;
}
void
xfs_wait_buftarg(
struct xfs_buftarg *btp)
{
LIST_HEAD(dispose);
int loop = 0;
/*
* First wait on the buftarg I/O count for all in-flight buffers to be
* released. This is critical as new buffers do not make the LRU until
* they are released.
*
* Next, flush the buffer workqueue to ensure all completion processing
* has finished. Just waiting on buffer locks is not sufficient for
* async IO as the reference count held over IO is not released until
* after the buffer lock is dropped. Hence we need to ensure here that
* all reference counts have been dropped before we start walking the
* LRU list.
*/
while (percpu_counter_sum(&btp->bt_io_count))
delay(100);
flush_workqueue(btp->bt_mount->m_buf_workqueue);
/* loop until there is nothing left on the lru list. */
while (list_lru_count(&btp->bt_lru)) {
list_lru_walk(&btp->bt_lru, xfs_buftarg_wait_rele,
&dispose, LONG_MAX);
while (!list_empty(&dispose)) {
struct xfs_buf *bp;
bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
list_del_init(&bp->b_lru);
if (bp->b_flags & XBF_WRITE_FAIL) {
xfs_alert(btp->bt_mount,
"Corruption Alert: Buffer at daddr 0x%llx had permanent write failures!",
(long long)bp->b_bn);
xfs_alert(btp->bt_mount,
"Please run xfs_repair to determine the extent of the problem.");
}
xfs_buf_rele(bp);
}
if (loop++ != 0)
delay(100);
}
}
static enum lru_status
xfs_buftarg_isolate(
struct list_head *item,
struct list_lru_one *lru,
spinlock_t *lru_lock,
void *arg)
{
struct xfs_buf *bp = container_of(item, struct xfs_buf, b_lru);
struct list_head *dispose = arg;
/*
* we are inverting the lru lock/bp->b_lock here, so use a trylock.
* If we fail to get the lock, just skip it.
*/
if (!spin_trylock(&bp->b_lock))
return LRU_SKIP;
/*
* Decrement the b_lru_ref count unless the value is already
* zero. If the value is already zero, we need to reclaim the
* buffer, otherwise it gets another trip through the LRU.
*/
if (atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
spin_unlock(&bp->b_lock);
return LRU_ROTATE;
}
bp->b_state |= XFS_BSTATE_DISPOSE;
list_lru_isolate_move(lru, item, dispose);
spin_unlock(&bp->b_lock);
return LRU_REMOVED;
}
static unsigned long
xfs_buftarg_shrink_scan(
struct shrinker *shrink,
struct shrink_control *sc)
{
struct xfs_buftarg *btp = container_of(shrink,
struct xfs_buftarg, bt_shrinker);
LIST_HEAD(dispose);
unsigned long freed;
freed = list_lru_shrink_walk(&btp->bt_lru, sc,
xfs_buftarg_isolate, &dispose);
while (!list_empty(&dispose)) {
struct xfs_buf *bp;
bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
list_del_init(&bp->b_lru);
xfs_buf_rele(bp);
}
return freed;
}
static unsigned long
xfs_buftarg_shrink_count(
struct shrinker *shrink,
struct shrink_control *sc)
{
struct xfs_buftarg *btp = container_of(shrink,
struct xfs_buftarg, bt_shrinker);
return list_lru_shrink_count(&btp->bt_lru, sc);
}
void
xfs_free_buftarg(
struct xfs_buftarg *btp)
{
unregister_shrinker(&btp->bt_shrinker);
ASSERT(percpu_counter_sum(&btp->bt_io_count) == 0);
percpu_counter_destroy(&btp->bt_io_count);
list_lru_destroy(&btp->bt_lru);
xfs_blkdev_issue_flush(btp);
kmem_free(btp);
}
int
xfs_setsize_buftarg(
xfs_buftarg_t *btp,
unsigned int sectorsize)
{
/* Set up metadata sector size info */
btp->bt_meta_sectorsize = sectorsize;
btp->bt_meta_sectormask = sectorsize - 1;
if (set_blocksize(btp->bt_bdev, sectorsize)) {
xfs_warn(btp->bt_mount,
"Cannot set_blocksize to %u on device %pg",
sectorsize, btp->bt_bdev);
return -EINVAL;
}
/* Set up device logical sector size mask */
btp->bt_logical_sectorsize = bdev_logical_block_size(btp->bt_bdev);
btp->bt_logical_sectormask = bdev_logical_block_size(btp->bt_bdev) - 1;
return 0;
}
/*
* When allocating the initial buffer target we have not yet
* read in the superblock, so don't know what sized sectors
* are being used at this early stage. Play safe.
*/
STATIC int
xfs_setsize_buftarg_early(
xfs_buftarg_t *btp,
struct block_device *bdev)
{
return xfs_setsize_buftarg(btp, bdev_logical_block_size(bdev));
}
xfs_buftarg_t *
xfs_alloc_buftarg(
struct xfs_mount *mp,
struct block_device *bdev,
struct dax_device *dax_dev)
{
xfs_buftarg_t *btp;
btp = kmem_zalloc(sizeof(*btp), KM_SLEEP | KM_NOFS);
btp->bt_mount = mp;
btp->bt_dev = bdev->bd_dev;
btp->bt_bdev = bdev;
btp->bt_daxdev = dax_dev;
if (xfs_setsize_buftarg_early(btp, bdev))
goto error_free;
if (list_lru_init(&btp->bt_lru))
goto error_free;
if (percpu_counter_init(&btp->bt_io_count, 0, GFP_KERNEL))
goto error_lru;
btp->bt_shrinker.count_objects = xfs_buftarg_shrink_count;
btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
btp->bt_shrinker.seeks = DEFAULT_SEEKS;
btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
if (register_shrinker(&btp->bt_shrinker))
goto error_pcpu;
return btp;
error_pcpu:
percpu_counter_destroy(&btp->bt_io_count);
error_lru:
list_lru_destroy(&btp->bt_lru);
error_free:
kmem_free(btp);
return NULL;
}
/*
* Cancel a delayed write list.
*
* Remove each buffer from the list, clear the delwri queue flag and drop the
* associated buffer reference.
*/
void
xfs_buf_delwri_cancel(
struct list_head *list)
{
struct xfs_buf *bp;
while (!list_empty(list)) {
bp = list_first_entry(list, struct xfs_buf, b_list);
xfs_buf_lock(bp);
bp->b_flags &= ~_XBF_DELWRI_Q;
list_del_init(&bp->b_list);
xfs_buf_relse(bp);
}
}
/*
* Add a buffer to the delayed write list.
*
* This queues a buffer for writeout if it hasn't already been. Note that
* neither this routine nor the buffer list submission functions perform
* any internal synchronization. It is expected that the lists are thread-local
* to the callers.
*
* Returns true if we queued up the buffer, or false if it already had
* been on the buffer list.
*/
bool
xfs_buf_delwri_queue(
struct xfs_buf *bp,
struct list_head *list)
{
ASSERT(xfs_buf_islocked(bp));
ASSERT(!(bp->b_flags & XBF_READ));
/*
* If the buffer is already marked delwri it already is queued up
* by someone else for imediate writeout. Just ignore it in that
* case.
*/
if (bp->b_flags & _XBF_DELWRI_Q) {
trace_xfs_buf_delwri_queued(bp, _RET_IP_);
return false;
}
trace_xfs_buf_delwri_queue(bp, _RET_IP_);
/*
* If a buffer gets written out synchronously or marked stale while it
* is on a delwri list we lazily remove it. To do this, the other party
* clears the _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
* It remains referenced and on the list. In a rare corner case it
* might get readded to a delwri list after the synchronous writeout, in
* which case we need just need to re-add the flag here.
*/
bp->b_flags |= _XBF_DELWRI_Q;
if (list_empty(&bp->b_list)) {
atomic_inc(&bp->b_hold);
list_add_tail(&bp->b_list, list);
}
return true;
}
/*
* Compare function is more complex than it needs to be because
* the return value is only 32 bits and we are doing comparisons
* on 64 bit values
*/
static int
xfs_buf_cmp(
void *priv,
struct list_head *a,
struct list_head *b)
{
struct xfs_buf *ap = container_of(a, struct xfs_buf, b_list);
struct xfs_buf *bp = container_of(b, struct xfs_buf, b_list);
xfs_daddr_t diff;
diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
if (diff < 0)
return -1;
if (diff > 0)
return 1;
return 0;
}
/*
* Submit buffers for write. If wait_list is specified, the buffers are
* submitted using sync I/O and placed on the wait list such that the caller can
* iowait each buffer. Otherwise async I/O is used and the buffers are released
* at I/O completion time. In either case, buffers remain locked until I/O
* completes and the buffer is released from the queue.
*/
static int
xfs_buf_delwri_submit_buffers(
struct list_head *buffer_list,
struct list_head *wait_list)
{
struct xfs_buf *bp, *n;
int pinned = 0;
struct blk_plug plug;
list_sort(NULL, buffer_list, xfs_buf_cmp);
blk_start_plug(&plug);
list_for_each_entry_safe(bp, n, buffer_list, b_list) {
if (!wait_list) {
if (xfs_buf_ispinned(bp)) {
pinned++;
continue;
}
if (!xfs_buf_trylock(bp))
continue;
} else {
xfs_buf_lock(bp);
}
/*
* Someone else might have written the buffer synchronously or
* marked it stale in the meantime. In that case only the
* _XBF_DELWRI_Q flag got cleared, and we have to drop the
* reference and remove it from the list here.
*/
if (!(bp->b_flags & _XBF_DELWRI_Q)) {
list_del_init(&bp->b_list);
xfs_buf_relse(bp);
continue;
}
trace_xfs_buf_delwri_split(bp, _RET_IP_);
/*
* If we have a wait list, each buffer (and associated delwri
* queue reference) transfers to it and is submitted
* synchronously. Otherwise, drop the buffer from the delwri
* queue and submit async.
*/
bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_WRITE_FAIL);
bp->b_flags |= XBF_WRITE;
if (wait_list) {
bp->b_flags &= ~XBF_ASYNC;
list_move_tail(&bp->b_list, wait_list);
} else {
bp->b_flags |= XBF_ASYNC;
list_del_init(&bp->b_list);
}
__xfs_buf_submit(bp, false);
}
blk_finish_plug(&plug);
return pinned;
}
/*
* Write out a buffer list asynchronously.
*
* This will take the @buffer_list, write all non-locked and non-pinned buffers
* out and not wait for I/O completion on any of the buffers. This interface
* is only safely useable for callers that can track I/O completion by higher
* level means, e.g. AIL pushing as the @buffer_list is consumed in this
* function.
*
* Note: this function will skip buffers it would block on, and in doing so
* leaves them on @buffer_list so they can be retried on a later pass. As such,
* it is up to the caller to ensure that the buffer list is fully submitted or
* cancelled appropriately when they are finished with the list. Failure to
* cancel or resubmit the list until it is empty will result in leaked buffers
* at unmount time.
*/
int
xfs_buf_delwri_submit_nowait(
struct list_head *buffer_list)
{
return xfs_buf_delwri_submit_buffers(buffer_list, NULL);
}
/*
* Write out a buffer list synchronously.
*
* This will take the @buffer_list, write all buffers out and wait for I/O
* completion on all of the buffers. @buffer_list is consumed by the function,
* so callers must have some other way of tracking buffers if they require such
* functionality.
*/
int
xfs_buf_delwri_submit(
struct list_head *buffer_list)
{
LIST_HEAD (wait_list);
int error = 0, error2;
struct xfs_buf *bp;
xfs_buf_delwri_submit_buffers(buffer_list, &wait_list);
/* Wait for IO to complete. */
while (!list_empty(&wait_list)) {
bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
list_del_init(&bp->b_list);
/*
* Wait on the locked buffer, check for errors and unlock and
* release the delwri queue reference.
*/
error2 = xfs_buf_iowait(bp);
xfs_buf_relse(bp);
if (!error)
error = error2;
}
return error;
}
/*
* Push a single buffer on a delwri queue.
*
* The purpose of this function is to submit a single buffer of a delwri queue
* and return with the buffer still on the original queue. The waiting delwri
* buffer submission infrastructure guarantees transfer of the delwri queue
* buffer reference to a temporary wait list. We reuse this infrastructure to
* transfer the buffer back to the original queue.
*
* Note the buffer transitions from the queued state, to the submitted and wait
* listed state and back to the queued state during this call. The buffer
* locking and queue management logic between _delwri_pushbuf() and
* _delwri_queue() guarantee that the buffer cannot be queued to another list
* before returning.
*/
int
xfs_buf_delwri_pushbuf(
struct xfs_buf *bp,
struct list_head *buffer_list)
{
LIST_HEAD (submit_list);
int error;
ASSERT(bp->b_flags & _XBF_DELWRI_Q);
trace_xfs_buf_delwri_pushbuf(bp, _RET_IP_);
/*
* Isolate the buffer to a new local list so we can submit it for I/O
* independently from the rest of the original list.
*/
xfs_buf_lock(bp);
list_move(&bp->b_list, &submit_list);
xfs_buf_unlock(bp);
/*
* Delwri submission clears the DELWRI_Q buffer flag and returns with
* the buffer on the wait list with the original reference. Rather than
* bounce the buffer from a local wait list back to the original list
* after I/O completion, reuse the original list as the wait list.
*/
xfs_buf_delwri_submit_buffers(&submit_list, buffer_list);
/*
* The buffer is now locked, under I/O and wait listed on the original
* delwri queue. Wait for I/O completion, restore the DELWRI_Q flag and
* return with the buffer unlocked and on the original queue.
*/
error = xfs_buf_iowait(bp);
bp->b_flags |= _XBF_DELWRI_Q;
xfs_buf_unlock(bp);
return error;
}
int __init
xfs_buf_init(void)
{
xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
KM_ZONE_HWALIGN, NULL);
if (!xfs_buf_zone)
goto out;
return 0;
out:
return -ENOMEM;
}
void
xfs_buf_terminate(void)
{
kmem_zone_destroy(xfs_buf_zone);
}
void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
{
/*
* Set the lru reference count to 0 based on the error injection tag.
* This allows userspace to disrupt buffer caching for debug/testing
* purposes.
*/
if (XFS_TEST_ERROR(false, bp->b_target->bt_mount,
XFS_ERRTAG_BUF_LRU_REF))
lru_ref = 0;
atomic_set(&bp->b_lru_ref, lru_ref);
}