linux/fs/xfs/xfs_buf.c
Dave Chinner 12eba65b28 xfs: Improve metadata buffer reclaim accountability
The buffer cache shrinker frees more than just the xfs_buf slab
objects - it also frees the pages attached to the buffers. Make sure
the memory reclaim code accounts for this memory being freed
correctly, similar to how the inode shrinker accounts for pages
freed from the page cache due to mapping invalidation.

We also need to make sure that the mm subsystem knows these are
reclaimable objects. We provide the memory reclaim subsystem with a
a shrinker to reclaim xfs_bufs, so we should really mark the slab
that way.

We also have a lot of xfs_bufs in a busy system, spread them around
like we do inodes.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2020-03-27 08:32:54 -07:00

2189 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/backing-dev.h>
#include "xfs_shared.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;
}
}
static int
_xfs_buf_alloc(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
struct xfs_buf **bpp)
{
struct xfs_buf *bp;
int error;
int i;
*bpp = NULL;
bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
if (unlikely(!bp))
return -ENOMEM;
/*
* 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_mount = target->bt_mount;
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_cache_free(xfs_buf_zone, bp);
return error;
}
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;
}
atomic_set(&bp->b_pin_count, 0);
init_waitqueue_head(&bp->b_waiters);
XFS_STATS_INC(bp->b_mount, xb_create);
trace_xfs_buf_init(bp, _RET_IP_);
*bpp = bp;
return 0;
}
/*
* 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
*/
static 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);
}
if (current->reclaim_state)
current->reclaim_state->reclaimed_slab +=
bp->b_page_count;
} else if (bp->b_flags & _XBF_KMEM)
kmem_free(bp->b_addr);
_xfs_buf_free_pages(bp);
xfs_buf_free_maps(bp);
kmem_cache_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;
xfs_km_flags_t kmflag_mask = 0;
/*
* assure zeroed buffer for non-read cases.
*/
if (!(flags & XBF_READ)) {
kmflag_mask |= KM_ZERO;
gfp_mask |= __GFP_ZERO;
}
/*
* 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) {
int align_mask = xfs_buftarg_dma_alignment(bp->b_target);
bp->b_addr = kmem_alloc_io(size, align_mask,
KM_NOFS | kmflag_mask);
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] = kmem_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_mount, xb_page_retries);
congestion_wait(BLK_RW_ASYNC, HZ/50);
goto retry;
}
XFS_STATS_INC(bp->b_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 auxiliary 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.
*/
int
xfs_buf_get_map(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
struct xfs_buf **bpp)
{
struct xfs_buf *bp;
struct xfs_buf *new_bp;
int error = 0;
*bpp = NULL;
error = xfs_buf_find(target, map, nmaps, flags, NULL, &bp);
if (!error)
goto found;
if (error != -ENOENT)
return error;
error = _xfs_buf_alloc(target, map, nmaps, flags, &new_bp);
if (error)
return error;
error = xfs_buf_allocate_memory(new_bp, flags);
if (error) {
xfs_buf_free(new_bp);
return error;
}
error = xfs_buf_find(target, map, nmaps, flags, new_bp, &bp);
if (error) {
xfs_buf_free(new_bp);
return error;
}
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_ratelimited(target->bt_mount,
"%s: failed to map %u pages", __func__,
bp->b_page_count);
xfs_buf_relse(bp);
return error;
}
}
/*
* 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_);
*bpp = bp;
return 0;
}
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);
}
/*
* Reverify a buffer found in cache without an attached ->b_ops.
*
* If the caller passed an ops structure and the buffer doesn't have ops
* assigned, set the ops and use it to verify the contents. If verification
* fails, clear XBF_DONE. We assume the buffer has no recorded errors and is
* already in XBF_DONE state on entry.
*
* Under normal operations, every in-core buffer is verified on read I/O
* completion. There are two scenarios that can lead to in-core buffers without
* an assigned ->b_ops. The first is during log recovery of buffers on a V4
* filesystem, though these buffers are purged at the end of recovery. The
* other is online repair, which intentionally reads with a NULL buffer ops to
* run several verifiers across an in-core buffer in order to establish buffer
* type. If repair can't establish that, the buffer will be left in memory
* with NULL buffer ops.
*/
int
xfs_buf_reverify(
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;
}
int
xfs_buf_read_map(
struct xfs_buftarg *target,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
struct xfs_buf **bpp,
const struct xfs_buf_ops *ops,
xfs_failaddr_t fa)
{
struct xfs_buf *bp;
int error;
flags |= XBF_READ;
*bpp = NULL;
error = xfs_buf_get_map(target, map, nmaps, flags, &bp);
if (error)
return error;
trace_xfs_buf_read(bp, flags, _RET_IP_);
if (!(bp->b_flags & XBF_DONE)) {
/* Initiate the buffer read and wait. */
XFS_STATS_INC(target->bt_mount, xb_get_read);
bp->b_ops = ops;
error = _xfs_buf_read(bp, flags);
/* Readahead iodone already dropped the buffer, so exit. */
if (flags & XBF_ASYNC)
return 0;
} else {
/* Buffer already read; all we need to do is check it. */
error = xfs_buf_reverify(bp, ops);
/* Readahead already finished; drop the buffer and exit. */
if (flags & XBF_ASYNC) {
xfs_buf_relse(bp);
return 0;
}
/* We do not want read in the flags */
bp->b_flags &= ~XBF_READ;
ASSERT(bp->b_ops != NULL || ops == NULL);
}
/*
* If we've had a read error, then the contents of the buffer are
* invalid and should not be used. To ensure that a followup read tries
* to pull the buffer from disk again, we clear the XBF_DONE flag and
* mark the buffer stale. This ensures that anyone who has a current
* reference to the buffer will interpret it's contents correctly and
* future cache lookups will also treat it as an empty, uninitialised
* buffer.
*/
if (error) {
if (!XFS_FORCED_SHUTDOWN(target->bt_mount))
xfs_buf_ioerror_alert(bp, fa);
bp->b_flags &= ~XBF_DONE;
xfs_buf_stale(bp);
xfs_buf_relse(bp);
/* bad CRC means corrupted metadata */
if (error == -EFSBADCRC)
error = -EFSCORRUPTED;
return error;
}
*bpp = bp;
return 0;
}
/*
* 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)
{
struct xfs_buf *bp;
if (bdi_read_congested(target->bt_bdev->bd_bdi))
return;
xfs_buf_read_map(target, map, nmaps,
XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD, &bp, ops,
__this_address);
}
/*
* 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;
int error;
*bpp = NULL;
error = xfs_buf_get_uncached(target, numblks, flags, &bp);
if (error)
return error;
/* 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) {
error = bp->b_error;
xfs_buf_relse(bp);
return error;
}
*bpp = bp;
return 0;
}
int
xfs_buf_get_uncached(
struct xfs_buftarg *target,
size_t numblks,
int flags,
struct xfs_buf **bpp)
{
unsigned long page_count;
int error, i;
struct xfs_buf *bp;
DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
*bpp = NULL;
/* flags might contain irrelevant bits, pass only what we care about */
error = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT, &bp);
if (error)
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]) {
error = -ENOMEM;
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_);
*bpp = bp;
return 0;
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_cache_free(xfs_buf_zone, bp);
fail:
return error;
}
/*
* 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_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_mount->m_buf_workqueue, &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,
xfs_failaddr_t func)
{
xfs_alert_ratelimited(bp->b_mount,
"metadata I/O error in \"%pS\" 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_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 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->bi_opf = op;
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 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;
if (bp->b_flags & XBF_WRITE) {
op = REQ_OP_WRITE;
/*
* 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_mount,
SHUTDOWN_CORRUPT_INCORE);
return;
}
} else if (bp->b_bn != XFS_BUF_DADDR_NULL) {
struct xfs_mount *mp = bp->b_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 {
op = REQ_OP_READ;
if (bp->b_flags & XBF_READ_AHEAD)
op |= REQ_RAHEAD;
}
/* we only use the buffer cache for meta-data */
op |= 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_length);
blk_start_plug(&plug);
for (i = 0; i < bp->b_map_count; i++) {
xfs_buf_ioapply_map(bp, i, &offset, &size, op);
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_mount)) {
xfs_buf_ioerror(bp, -EIO);
bp->b_flags &= ~XBF_DONE;
xfs_buf_stale(bp);
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));
}
void
xfs_buf_zero(
struct xfs_buf *bp,
size_t boff,
size_t bsize)
{
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_length) - boff);
ASSERT((csize + page_offset) <= PAGE_SIZE);
memset(page_address(page) + page_offset, 0, csize);
boff += csize;
}
}
/*
* Log a message about and stale a buffer that a caller has decided is corrupt.
*
* This function should be called for the kinds of metadata corruption that
* cannot be detect from a verifier, such as incorrect inter-block relationship
* data. Do /not/ call this function from a verifier function.
*
* The buffer must be XBF_DONE prior to the call. Afterwards, the buffer will
* be marked stale, but b_error will not be set. The caller is responsible for
* releasing the buffer or fixing it.
*/
void
__xfs_buf_mark_corrupt(
struct xfs_buf *bp,
xfs_failaddr_t fa)
{
ASSERT(bp->b_flags & XBF_DONE);
xfs_buf_corruption_error(bp, fa);
xfs_buf_stale(bp);
}
/*
* 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_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_cache_create("xfs_buf", sizeof(struct xfs_buf), 0,
SLAB_HWCACHE_ALIGN |
SLAB_RECLAIM_ACCOUNT |
SLAB_MEM_SPREAD,
NULL);
if (!xfs_buf_zone)
goto out;
return 0;
out:
return -ENOMEM;
}
void
xfs_buf_terminate(void)
{
kmem_cache_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_mount, XFS_ERRTAG_BUF_LRU_REF))
lru_ref = 0;
atomic_set(&bp->b_lru_ref, lru_ref);
}
/*
* Verify an on-disk magic value against the magic value specified in the
* verifier structure. The verifier magic is in disk byte order so the caller is
* expected to pass the value directly from disk.
*/
bool
xfs_verify_magic(
struct xfs_buf *bp,
__be32 dmagic)
{
struct xfs_mount *mp = bp->b_mount;
int idx;
idx = xfs_sb_version_hascrc(&mp->m_sb);
if (WARN_ON(!bp->b_ops || !bp->b_ops->magic[idx]))
return false;
return dmagic == bp->b_ops->magic[idx];
}
/*
* Verify an on-disk magic value against the magic value specified in the
* verifier structure. The verifier magic is in disk byte order so the caller is
* expected to pass the value directly from disk.
*/
bool
xfs_verify_magic16(
struct xfs_buf *bp,
__be16 dmagic)
{
struct xfs_mount *mp = bp->b_mount;
int idx;
idx = xfs_sb_version_hascrc(&mp->m_sb);
if (WARN_ON(!bp->b_ops || !bp->b_ops->magic16[idx]))
return false;
return dmagic == bp->b_ops->magic16[idx];
}