// SPDX-License-Identifier: GPL-2.0 /* * Copyright (c) 2000-2006 Silicon Graphics, Inc. * All Rights Reserved. */ #include "xfs.h" #include #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); } } 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; } } /* * 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, 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]; }