fs/bcachefs/fs-io-pagecache.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 #ifndef NO_BCACHEFS_FS

 #include "bcachefs.h"
 #include "btree_iter.h"
 #include "extents.h"
 #include "fs-io.h"
 #include "fs-io-pagecache.h"
 #include "subvolume.h"

 #include <linux/pagevec.h>
 #include <linux/writeback.h>

 int bch2_filemap_get_contig_folios_d(struct address_space *mapping,
 				     loff_t start, u64 end,
 				     fgf_t fgp_flags, gfp_t gfp,
 				     folios *fs)
 {
 	struct folio *f;
 	u64 pos = start;
 	int ret = 0;

 	while (pos < end) {
 		if ((u64) pos >= (u64) start + (1ULL << 20))
 			fgp_flags &= ~FGP_CREAT;

 		ret = darray_make_room_gfp(fs, 1, gfp & GFP_KERNEL);
 		if (ret)
 			break;

 		f = __filemap_get_folio(mapping, pos >> PAGE_SHIFT, fgp_flags, gfp);
 		if (IS_ERR_OR_NULL(f))
 			break;

 		BUG_ON(fs->nr && folio_pos(f) != pos);

 		pos = folio_end_pos(f);
 		darray_push(fs, f);
 	}

 	if (!fs->nr && !ret && (fgp_flags & FGP_CREAT))
 		ret = -ENOMEM;

 	return fs->nr ? 0 : ret;
 }

 /* pagecache_block must be held */
 int bch2_write_invalidate_inode_pages_range(struct address_space *mapping,
 					    loff_t start, loff_t end)
 {
 	int ret;

 	/*
 	 * XXX: the way this is currently implemented, we can spin if a process
 	 * is continually redirtying a specific page
 	 */
 	do {
 		if (!mapping->nrpages)
 			return 0;

 		ret = filemap_write_and_wait_range(mapping, start, end);
 		if (ret)
 			break;

 		if (!mapping->nrpages)
 			return 0;

 		ret = invalidate_inode_pages2_range(mapping,
 				start >> PAGE_SHIFT,
 				end >> PAGE_SHIFT);
 	} while (ret == -EBUSY);

 	return ret;
 }

 #if 0
 /* Useful for debug tracing: */
 static const char * const bch2_folio_sector_states[] = {
 #define x(n)	#n,
 	BCH_FOLIO_SECTOR_STATE()
 #undef x
 	NULL
 };
 #endif

 static inline enum bch_folio_sector_state
 folio_sector_dirty(enum bch_folio_sector_state state)
 {
 	switch (state) {
 	case SECTOR_unallocated:
 		return SECTOR_dirty;
 	case SECTOR_reserved:
 		return SECTOR_dirty_reserved;
 	default:
 		return state;
 	}
 }

 static inline enum bch_folio_sector_state
 folio_sector_undirty(enum bch_folio_sector_state state)
 {
 	switch (state) {
 	case SECTOR_dirty:
 		return SECTOR_unallocated;
 	case SECTOR_dirty_reserved:
 		return SECTOR_reserved;
 	default:
 		return state;
 	}
 }

 static inline enum bch_folio_sector_state
 folio_sector_reserve(enum bch_folio_sector_state state)
 {
 	switch (state) {
 	case SECTOR_unallocated:
 		return SECTOR_reserved;
 	case SECTOR_dirty:
 		return SECTOR_dirty_reserved;
 	default:
 		return state;
 	}
 }

 /* for newly allocated folios: */
 struct bch_folio *__bch2_folio_create(struct folio *folio, gfp_t gfp)
 {
 	struct bch_folio *s;

 	s = kzalloc(sizeof(*s) +
 		    sizeof(struct bch_folio_sector) *
 		    folio_sectors(folio), gfp);
 	if (!s)
 		return NULL;

 	spin_lock_init(&s->lock);
 	folio_attach_private(folio, s);
 	return s;
 }

 struct bch_folio *bch2_folio_create(struct folio *folio, gfp_t gfp)
 {
 	return bch2_folio(folio) ?: __bch2_folio_create(folio, gfp);
 }

 static unsigned bkey_to_sector_state(struct bkey_s_c k)
 {
 	if (bkey_extent_is_reservation(k))
 		return SECTOR_reserved;
 	if (bkey_extent_is_allocation(k.k))
 		return SECTOR_allocated;
 	return SECTOR_unallocated;
 }

 static void __bch2_folio_set(struct folio *folio,
 			     unsigned pg_offset, unsigned pg_len,
 			     unsigned nr_ptrs, unsigned state)
 {
 	struct bch_folio *s = bch2_folio(folio);
 	unsigned i, sectors = folio_sectors(folio);

 	BUG_ON(pg_offset >= sectors);
 	BUG_ON(pg_offset + pg_len > sectors);

 	spin_lock(&s->lock);

 	for (i = pg_offset; i < pg_offset + pg_len; i++) {
 		s->s[i].nr_replicas	= nr_ptrs;
 		bch2_folio_sector_set(folio, s, i, state);
 	}

 	if (i == sectors)
 		s->uptodate = true;

 	spin_unlock(&s->lock);
 }

 /*
  * Initialize bch_folio state (allocated/unallocated, nr_replicas) from the
  * extents btree:
  */
 int bch2_folio_set(struct bch_fs *c, subvol_inum inum,
 		   struct folio **fs, unsigned nr_folios)
 {
 	u64 offset = folio_sector(fs[0]);
 	bool need_set = false;

 	for (unsigned folio_idx = 0; folio_idx < nr_folios; folio_idx++) {
 		struct bch_folio *s = bch2_folio_create(fs[folio_idx], GFP_KERNEL);
 		if (!s)
 			return -ENOMEM;

 		need_set |= !s->uptodate;
 	}

 	if (!need_set)
 		return 0;

 	unsigned folio_idx = 0;

 	return bch2_trans_run(c,
 		for_each_btree_key_in_subvolume_upto(trans, iter, BTREE_ID_extents,
 				   POS(inum.inum, offset),
 				   POS(inum.inum, U64_MAX),
 				   inum.subvol, BTREE_ITER_slots, k, ({
 			unsigned nr_ptrs = bch2_bkey_nr_ptrs_fully_allocated(k);
 			unsigned state = bkey_to_sector_state(k);

 			while (folio_idx < nr_folios) {
 				struct folio *folio = fs[folio_idx];
 				u64 folio_start	= folio_sector(folio);
 				u64 folio_end	= folio_end_sector(folio);
 				unsigned folio_offset = max(bkey_start_offset(k.k), folio_start) -
 					folio_start;
 				unsigned folio_len = min(k.k->p.offset, folio_end) -
 					folio_offset - folio_start;

 				BUG_ON(k.k->p.offset < folio_start);
 				BUG_ON(bkey_start_offset(k.k) > folio_end);

 				if (!bch2_folio(folio)->uptodate)
 					__bch2_folio_set(folio, folio_offset, folio_len, nr_ptrs, state);

 				if (k.k->p.offset < folio_end)
 					break;
 				folio_idx++;
 			}

 			if (folio_idx == nr_folios)
 				break;
 			0;
 		})));
 }

 void bch2_bio_page_state_set(struct bio *bio, struct bkey_s_c k)
 {
 	struct bvec_iter iter;
 	struct folio_vec fv;
 	unsigned nr_ptrs = k.k->type == KEY_TYPE_reflink_v
 		? 0 : bch2_bkey_nr_ptrs_fully_allocated(k);
 	unsigned state = bkey_to_sector_state(k);

 	bio_for_each_folio(fv, bio, iter)
 		__bch2_folio_set(fv.fv_folio,
 				 fv.fv_offset >> 9,
 				 fv.fv_len >> 9,
 				 nr_ptrs, state);
 }

 void bch2_mark_pagecache_unallocated(struct bch_inode_info *inode,
 				     u64 start, u64 end)
 {
 	pgoff_t index = start >> PAGE_SECTORS_SHIFT;
 	pgoff_t end_index = (end - 1) >> PAGE_SECTORS_SHIFT;
 	struct folio_batch fbatch;
 	unsigned i, j;

 	if (end <= start)
 		return;

 	folio_batch_init(&fbatch);

 	while (filemap_get_folios(inode->v.i_mapping,
 				  &index, end_index, &fbatch)) {
 		for (i = 0; i < folio_batch_count(&fbatch); i++) {
 			struct folio *folio = fbatch.folios[i];
 			u64 folio_start = folio_sector(folio);
 			u64 folio_end = folio_end_sector(folio);
 			unsigned folio_offset = max(start, folio_start) - folio_start;
 			unsigned folio_len = min(end, folio_end) - folio_offset - folio_start;
 			struct bch_folio *s;

 			BUG_ON(end <= folio_start);

 			folio_lock(folio);
 			s = bch2_folio(folio);

 			if (s) {
 				spin_lock(&s->lock);
 				for (j = folio_offset; j < folio_offset + folio_len; j++)
 					s->s[j].nr_replicas = 0;
 				spin_unlock(&s->lock);
 			}

 			folio_unlock(folio);
 		}
 		folio_batch_release(&fbatch);
 		cond_resched();
 	}
 }

 int bch2_mark_pagecache_reserved(struct bch_inode_info *inode,
 				 u64 *start, u64 end,
 				 bool nonblocking)
 {
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
 	pgoff_t index = *start >> PAGE_SECTORS_SHIFT;
 	pgoff_t end_index = (end - 1) >> PAGE_SECTORS_SHIFT;
 	struct folio_batch fbatch;
 	s64 i_sectors_delta = 0;
 	int ret = 0;

 	if (end <= *start)
 		return 0;

 	folio_batch_init(&fbatch);

 	while (filemap_get_folios(inode->v.i_mapping,
 				  &index, end_index, &fbatch)) {
 		for (unsigned i = 0; i < folio_batch_count(&fbatch); i++) {
 			struct folio *folio = fbatch.folios[i];

 			if (!nonblocking)
 				folio_lock(folio);
 			else if (!folio_trylock(folio)) {
 				folio_batch_release(&fbatch);
 				ret = -EAGAIN;
 				break;
 			}

 			u64 folio_start = folio_sector(folio);
 			u64 folio_end = folio_end_sector(folio);

 			BUG_ON(end <= folio_start);

 			*start = min(end, folio_end);

 			struct bch_folio *s = bch2_folio(folio);
 			if (s) {
 				unsigned folio_offset = max(*start, folio_start) - folio_start;
 				unsigned folio_len = min(end, folio_end) - folio_offset - folio_start;

 				spin_lock(&s->lock);
 				for (unsigned j = folio_offset; j < folio_offset + folio_len; j++) {
 					i_sectors_delta -= s->s[j].state == SECTOR_dirty;
 					bch2_folio_sector_set(folio, s, j,
 						folio_sector_reserve(s->s[j].state));
 				}
 				spin_unlock(&s->lock);
 			}

 			folio_unlock(folio);
 		}
 		folio_batch_release(&fbatch);
 		cond_resched();
 	}

 	bch2_i_sectors_acct(c, inode, NULL, i_sectors_delta);
 	return ret;
 }

 static inline unsigned sectors_to_reserve(struct bch_folio_sector *s,
 					  unsigned nr_replicas)
 {
 	return max(0, (int) nr_replicas -
 		   s->nr_replicas -
 		   s->replicas_reserved);
 }

 int bch2_get_folio_disk_reservation(struct bch_fs *c,
 				struct bch_inode_info *inode,
 				struct folio *folio, bool check_enospc)
 {
 	struct bch_folio *s = bch2_folio_create(folio, 0);
 	unsigned nr_replicas = inode_nr_replicas(c, inode);
 	struct disk_reservation disk_res = { 0 };
 	unsigned i, sectors = folio_sectors(folio), disk_res_sectors = 0;
 	int ret;

 	if (!s)
 		return -ENOMEM;

 	for (i = 0; i < sectors; i++)
 		disk_res_sectors += sectors_to_reserve(&s->s[i], nr_replicas);

 	if (!disk_res_sectors)
 		return 0;

 	ret = bch2_disk_reservation_get(c, &disk_res,
 					disk_res_sectors, 1,
 					!check_enospc
 					? BCH_DISK_RESERVATION_NOFAIL
 					: 0);
 	if (unlikely(ret))
 		return ret;

 	for (i = 0; i < sectors; i++)
 		s->s[i].replicas_reserved +=
 			sectors_to_reserve(&s->s[i], nr_replicas);

 	return 0;
 }

 void bch2_folio_reservation_put(struct bch_fs *c,
 			struct bch_inode_info *inode,
 			struct bch2_folio_reservation *res)
 {
 	bch2_disk_reservation_put(c, &res->disk);
 	bch2_quota_reservation_put(c, inode, &res->quota);
 }

 static int __bch2_folio_reservation_get(struct bch_fs *c,
 			struct bch_inode_info *inode,
 			struct folio *folio,
 			struct bch2_folio_reservation *res,
 			size_t offset, size_t len,
 			bool partial)
 {
 	struct bch_folio *s = bch2_folio_create(folio, 0);
 	unsigned i, disk_sectors = 0, quota_sectors = 0;
 	struct disk_reservation disk_res = {};
 	size_t reserved = len;
 	int ret;

 	if (!s)
 		return -ENOMEM;

 	BUG_ON(!s->uptodate);

 	for (i = round_down(offset, block_bytes(c)) >> 9;
 	     i < round_up(offset + len, block_bytes(c)) >> 9;
 	     i++) {
 		disk_sectors += sectors_to_reserve(&s->s[i], res->disk.nr_replicas);
 		quota_sectors += s->s[i].state == SECTOR_unallocated;
 	}

 	if (disk_sectors) {
 		ret = bch2_disk_reservation_add(c, &disk_res, disk_sectors,
 				partial ? BCH_DISK_RESERVATION_PARTIAL : 0);
 		if (unlikely(ret))
 			return ret;

 		if (unlikely(disk_res.sectors != disk_sectors)) {
 			disk_sectors = quota_sectors = 0;

 			for (i = round_down(offset, block_bytes(c)) >> 9;
 			     i < round_up(offset + len, block_bytes(c)) >> 9;
 			     i++) {
 				disk_sectors += sectors_to_reserve(&s->s[i], res->disk.nr_replicas);
 				if (disk_sectors > disk_res.sectors) {
 					/*
 					 * Make sure to get a reservation that's
 					 * aligned to the filesystem blocksize:
 					 */
 					unsigned reserved_offset = round_down(i << 9, block_bytes(c));
 					reserved = clamp(reserved_offset, offset, offset + len) - offset;

 					if (!reserved) {
 						bch2_disk_reservation_put(c, &disk_res);
 						return -BCH_ERR_ENOSPC_disk_reservation;
 					}
 					break;
 				}
 				quota_sectors += s->s[i].state == SECTOR_unallocated;
 			}
 		}
 	}

 	if (quota_sectors) {
 		ret = bch2_quota_reservation_add(c, inode, &res->quota, quota_sectors, true);
 		if (unlikely(ret)) {
 			bch2_disk_reservation_put(c, &disk_res);
 			return ret;
 		}
 	}

 	res->disk.sectors += disk_res.sectors;
 	return partial ? reserved : 0;
 }

 int bch2_folio_reservation_get(struct bch_fs *c,
 			struct bch_inode_info *inode,
 			struct folio *folio,
 			struct bch2_folio_reservation *res,
 			size_t offset, size_t len)
 {
 	return __bch2_folio_reservation_get(c, inode, folio, res, offset, len, false);
 }

 ssize_t bch2_folio_reservation_get_partial(struct bch_fs *c,
 			struct bch_inode_info *inode,
 			struct folio *folio,
 			struct bch2_folio_reservation *res,
 			size_t offset, size_t len)
 {
 	return __bch2_folio_reservation_get(c, inode, folio, res, offset, len, true);
 }

 static void bch2_clear_folio_bits(struct folio *folio)
 {
 	struct bch_inode_info *inode = to_bch_ei(folio->mapping->host);
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
 	struct bch_folio *s = bch2_folio(folio);
 	struct disk_reservation disk_res = { 0 };
 	int i, sectors = folio_sectors(folio), dirty_sectors = 0;

 	if (!s)
 		return;

 	EBUG_ON(!folio_test_locked(folio));
 	EBUG_ON(folio_test_writeback(folio));

 	for (i = 0; i < sectors; i++) {
 		disk_res.sectors += s->s[i].replicas_reserved;
 		s->s[i].replicas_reserved = 0;

 		dirty_sectors -= s->s[i].state == SECTOR_dirty;
 		bch2_folio_sector_set(folio, s, i, folio_sector_undirty(s->s[i].state));
 	}

 	bch2_disk_reservation_put(c, &disk_res);

 	bch2_i_sectors_acct(c, inode, NULL, dirty_sectors);

 	bch2_folio_release(folio);
 }

 void bch2_set_folio_dirty(struct bch_fs *c,
 			  struct bch_inode_info *inode,
 			  struct folio *folio,
 			  struct bch2_folio_reservation *res,
 			  unsigned offset, unsigned len)
 {
 	struct bch_folio *s = bch2_folio(folio);
 	unsigned i, dirty_sectors = 0;

 	WARN_ON((u64) folio_pos(folio) + offset + len >
 		round_up((u64) i_size_read(&inode->v), block_bytes(c)));

 	BUG_ON(!s->uptodate);

 	spin_lock(&s->lock);

 	for (i = round_down(offset, block_bytes(c)) >> 9;
 	     i < round_up(offset + len, block_bytes(c)) >> 9;
 	     i++) {
 		unsigned sectors = sectors_to_reserve(&s->s[i],
 						res->disk.nr_replicas);

 		/*
 		 * This can happen if we race with the error path in
 		 * bch2_writepage_io_done():
 		 */
 		sectors = min_t(unsigned, sectors, res->disk.sectors);

 		s->s[i].replicas_reserved += sectors;
 		res->disk.sectors -= sectors;

 		dirty_sectors += s->s[i].state == SECTOR_unallocated;

 		bch2_folio_sector_set(folio, s, i, folio_sector_dirty(s->s[i].state));
 	}

 	spin_unlock(&s->lock);

 	bch2_i_sectors_acct(c, inode, &res->quota, dirty_sectors);

 	if (!folio_test_dirty(folio))
 		filemap_dirty_folio(inode->v.i_mapping, folio);
 }

 vm_fault_t bch2_page_fault(struct vm_fault *vmf)
 {
 	struct file *file = vmf->vma->vm_file;
 	struct address_space *mapping = file->f_mapping;
 	struct address_space *fdm = faults_disabled_mapping();
 	struct bch_inode_info *inode = file_bch_inode(file);
 	vm_fault_t ret;

 	if (fdm == mapping)
 		return VM_FAULT_SIGBUS;

 	/* Lock ordering: */
 	if (fdm > mapping) {
 		struct bch_inode_info *fdm_host = to_bch_ei(fdm->host);

 		if (bch2_pagecache_add_tryget(inode))
 			goto got_lock;

 		bch2_pagecache_block_put(fdm_host);

 		bch2_pagecache_add_get(inode);
 		bch2_pagecache_add_put(inode);

 		bch2_pagecache_block_get(fdm_host);

 		/* Signal that lock has been dropped: */
 		set_fdm_dropped_locks();
 		return VM_FAULT_SIGBUS;
 	}

 	bch2_pagecache_add_get(inode);
 got_lock:
 	ret = filemap_fault(vmf);
 	bch2_pagecache_add_put(inode);

 	return ret;
 }

 vm_fault_t bch2_page_mkwrite(struct vm_fault *vmf)
 {
 	struct folio *folio = page_folio(vmf->page);
 	struct file *file = vmf->vma->vm_file;
 	struct bch_inode_info *inode = file_bch_inode(file);
 	struct address_space *mapping = file->f_mapping;
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
 	struct bch2_folio_reservation res;
 	unsigned len;
 	loff_t isize;
 	vm_fault_t ret;

 	bch2_folio_reservation_init(c, inode, &res);

 	sb_start_pagefault(inode->v.i_sb);
 	file_update_time(file);

 	/*
 	 * Not strictly necessary, but helps avoid dio writes livelocking in
 	 * bch2_write_invalidate_inode_pages_range() - can drop this if/when we get
 	 * a bch2_write_invalidate_inode_pages_range() that works without dropping
 	 * page lock before invalidating page
 	 */
 	bch2_pagecache_add_get(inode);

 	folio_lock(folio);
 	isize = i_size_read(&inode->v);

 	if (folio->mapping != mapping || folio_pos(folio) >= isize) {
 		folio_unlock(folio);
 		ret = VM_FAULT_NOPAGE;
 		goto out;
 	}

 	len = min_t(loff_t, folio_size(folio), isize - folio_pos(folio));

 	if (bch2_folio_set(c, inode_inum(inode), &folio, 1) ?:
 	    bch2_folio_reservation_get(c, inode, folio, &res, 0, len)) {
 		folio_unlock(folio);
 		ret = VM_FAULT_SIGBUS;
 		goto out;
 	}

 	bch2_set_folio_dirty(c, inode, folio, &res, 0, len);
 	bch2_folio_reservation_put(c, inode, &res);

 	folio_wait_stable(folio);
 	ret = VM_FAULT_LOCKED;
 out:
 	bch2_pagecache_add_put(inode);
 	sb_end_pagefault(inode->v.i_sb);

 	return ret;
 }

 void bch2_invalidate_folio(struct folio *folio, size_t offset, size_t length)
 {
 	if (offset || length < folio_size(folio))
 		return;

 	bch2_clear_folio_bits(folio);
 }

 bool bch2_release_folio(struct folio *folio, gfp_t gfp_mask)
 {
 	if (folio_test_dirty(folio) || folio_test_writeback(folio))
 		return false;

 	bch2_clear_folio_bits(folio);
 	return true;
 }

 /* fseek: */

 static int folio_data_offset(struct folio *folio, loff_t pos,
 			     unsigned min_replicas)
 {
 	struct bch_folio *s = bch2_folio(folio);
 	unsigned i, sectors = folio_sectors(folio);

 	if (s)
 		for (i = folio_pos_to_s(folio, pos); i < sectors; i++)
 			if (s->s[i].state >= SECTOR_dirty &&
 			    s->s[i].nr_replicas + s->s[i].replicas_reserved >= min_replicas)
 				return i << SECTOR_SHIFT;

 	return -1;
 }

 loff_t bch2_seek_pagecache_data(struct inode *vinode,
 				loff_t start_offset,
 				loff_t end_offset,
 				unsigned min_replicas,
 				bool nonblock)
 {
 	struct folio_batch fbatch;
 	pgoff_t start_index	= start_offset >> PAGE_SHIFT;
 	pgoff_t end_index	= end_offset >> PAGE_SHIFT;
 	pgoff_t index		= start_index;
 	unsigned i;
 	loff_t ret;
 	int offset;

 	folio_batch_init(&fbatch);

 	while (filemap_get_folios(vinode->i_mapping,
 				  &index, end_index, &fbatch)) {
 		for (i = 0; i < folio_batch_count(&fbatch); i++) {
 			struct folio *folio = fbatch.folios[i];

 			if (!nonblock) {
 				folio_lock(folio);
 			} else if (!folio_trylock(folio)) {
 				folio_batch_release(&fbatch);
 				return -EAGAIN;
 			}

 			offset = folio_data_offset(folio,
 					max(folio_pos(folio), start_offset),
 					min_replicas);
 			if (offset >= 0) {
 				ret = clamp(folio_pos(folio) + offset,
 					    start_offset, end_offset);
 				folio_unlock(folio);
 				folio_batch_release(&fbatch);
 				return ret;
 			}
 			folio_unlock(folio);
 		}
 		folio_batch_release(&fbatch);
 		cond_resched();
 	}

 	return end_offset;
 }

 /*
  * Search for a hole in a folio.
  *
  * The filemap layer returns -ENOENT if no folio exists, so reuse the same error
  * code to indicate a pagecache hole exists at the returned offset. Otherwise
  * return 0 if the folio is filled with data, or an error code. This function
  * can return -EAGAIN if nonblock is specified.
  */
 static int folio_hole_offset(struct address_space *mapping, loff_t *offset,
 			      unsigned min_replicas, bool nonblock)
 {
 	struct folio *folio;
 	struct bch_folio *s;
 	unsigned i, sectors;
 	int ret = -ENOENT;

 	folio = __filemap_get_folio(mapping, *offset >> PAGE_SHIFT,
 				    FGP_LOCK|(nonblock ? FGP_NOWAIT : 0), 0);
 	if (IS_ERR(folio))
 		return PTR_ERR(folio);

 	s = bch2_folio(folio);
 	if (!s)
 		goto unlock;

 	sectors = folio_sectors(folio);
 	for (i = folio_pos_to_s(folio, *offset); i < sectors; i++)
 		if (s->s[i].state < SECTOR_dirty ||
 		    s->s[i].nr_replicas + s->s[i].replicas_reserved < min_replicas) {
 			*offset = max(*offset,
 				      folio_pos(folio) + (i << SECTOR_SHIFT));
 			goto unlock;
 		}

 	*offset = folio_end_pos(folio);
 	ret = 0;
 unlock:
 	folio_unlock(folio);
 	folio_put(folio);
 	return ret;
 }

 loff_t bch2_seek_pagecache_hole(struct inode *vinode,
 				loff_t start_offset,
 				loff_t end_offset,
 				unsigned min_replicas,
 				bool nonblock)
 {
 	struct address_space *mapping = vinode->i_mapping;
 	loff_t offset = start_offset;
 	loff_t ret = 0;

 	while (!ret && offset < end_offset)
 		ret = folio_hole_offset(mapping, &offset, min_replicas, nonblock);

 	if (ret && ret != -ENOENT)
 		return ret;
 	return min(offset, end_offset);
 }

 int bch2_clamp_data_hole(struct inode *inode,
 			 u64 *hole_start,
 			 u64 *hole_end,
 			 unsigned min_replicas,
 			 bool nonblock)
 {
 	loff_t ret;

 	ret = bch2_seek_pagecache_hole(inode,
 		*hole_start << 9, *hole_end << 9, min_replicas, nonblock) >> 9;
 	if (ret < 0)
 		return ret;

 	*hole_start = ret;

 	if (*hole_start == *hole_end)
 		return 0;

 	ret = bch2_seek_pagecache_data(inode,
 		*hole_start << 9, *hole_end << 9, min_replicas, nonblock) >> 9;
 	if (ret < 0)
 		return ret;

 	*hole_end = ret;
 	return 0;
 }

 #endif /* NO_BCACHEFS_FS */
	// SPDX-License-Identifier: GPL-2.0
	#ifndef NO_BCACHEFS_FS

	#include "bcachefs.h"
	#include "btree_iter.h"
	#include "extents.h"
	#include "fs-io.h"
	#include "fs-io-pagecache.h"
	#include "subvolume.h"

	#include <linux/pagevec.h>
	#include <linux/writeback.h>

	int bch2_filemap_get_contig_folios_d(struct address_space *mapping,
	loff_t start, u64 end,
	fgf_t fgp_flags, gfp_t gfp,
	folios *fs)
	{
	struct folio *f;
	u64 pos = start;
	int ret = 0;

	while (pos < end) {
	if ((u64) pos >= (u64) start + (1ULL << 20))
	fgp_flags &= ~FGP_CREAT;

	ret = darray_make_room_gfp(fs, 1, gfp & GFP_KERNEL);
	if (ret)
	break;

	f = __filemap_get_folio(mapping, pos >> PAGE_SHIFT, fgp_flags, gfp);
	if (IS_ERR_OR_NULL(f))
	break;

	BUG_ON(fs->nr && folio_pos(f) != pos);

	pos = folio_end_pos(f);
	darray_push(fs, f);
	}

	if (!fs->nr && !ret && (fgp_flags & FGP_CREAT))
	ret = -ENOMEM;

	return fs->nr ? 0 : ret;
	}

	/* pagecache_block must be held */
	int bch2_write_invalidate_inode_pages_range(struct address_space *mapping,
	loff_t start, loff_t end)
	{
	int ret;

	/*
	* XXX: the way this is currently implemented, we can spin if a process
	* is continually redirtying a specific page
	*/
	do {
	if (!mapping->nrpages)
	return 0;

	ret = filemap_write_and_wait_range(mapping, start, end);
	if (ret)
	break;

	if (!mapping->nrpages)
	return 0;

	ret = invalidate_inode_pages2_range(mapping,
	start >> PAGE_SHIFT,
	end >> PAGE_SHIFT);
	} while (ret == -EBUSY);

	return ret;
	}

	#if 0
	/* Useful for debug tracing: */
	static const char * const bch2_folio_sector_states[] = {
	#define x(n) #n,
	BCH_FOLIO_SECTOR_STATE()
	#undef x
	NULL
	};
	#endif

	static inline enum bch_folio_sector_state
	folio_sector_dirty(enum bch_folio_sector_state state)
	{
	switch (state) {
	case SECTOR_unallocated:
	return SECTOR_dirty;
	case SECTOR_reserved:
	return SECTOR_dirty_reserved;
	default:
	return state;
	}
	}

	static inline enum bch_folio_sector_state
	folio_sector_undirty(enum bch_folio_sector_state state)
	{
	switch (state) {
	case SECTOR_dirty:
	return SECTOR_unallocated;
	case SECTOR_dirty_reserved:
	return SECTOR_reserved;
	default:
	return state;
	}
	}

	static inline enum bch_folio_sector_state
	folio_sector_reserve(enum bch_folio_sector_state state)
	{
	switch (state) {
	case SECTOR_unallocated:
	return SECTOR_reserved;
	case SECTOR_dirty:
	return SECTOR_dirty_reserved;
	default:
	return state;
	}
	}

	/* for newly allocated folios: */
	struct bch_folio __bch2_folio_create(struct folio folio, gfp_t gfp)
	{
	struct bch_folio *s;

	s = kzalloc(sizeof(*s) +
	sizeof(struct bch_folio_sector) *
	folio_sectors(folio), gfp);
	if (!s)
	return NULL;

	spin_lock_init(&s->lock);
	folio_attach_private(folio, s);
	return s;
	}

	struct bch_folio bch2_folio_create(struct folio folio, gfp_t gfp)
	{
	return bch2_folio(folio) ?: __bch2_folio_create(folio, gfp);
	}

	static unsigned bkey_to_sector_state(struct bkey_s_c k)
	{
	if (bkey_extent_is_reservation(k))
	return SECTOR_reserved;
	if (bkey_extent_is_allocation(k.k))
	return SECTOR_allocated;
	return SECTOR_unallocated;
	}

	static void __bch2_folio_set(struct folio *folio,
	unsigned pg_offset, unsigned pg_len,
	unsigned nr_ptrs, unsigned state)
	{
	struct bch_folio *s = bch2_folio(folio);
	unsigned i, sectors = folio_sectors(folio);

	BUG_ON(pg_offset >= sectors);
	BUG_ON(pg_offset + pg_len > sectors);

	spin_lock(&s->lock);

	for (i = pg_offset; i < pg_offset + pg_len; i++) {
	s->s[i].nr_replicas = nr_ptrs;
	bch2_folio_sector_set(folio, s, i, state);
	}

	if (i == sectors)
	s->uptodate = true;

	spin_unlock(&s->lock);
	}

	/*
	* Initialize bch_folio state (allocated/unallocated, nr_replicas) from the
	* extents btree:
	*/
	int bch2_folio_set(struct bch_fs *c, subvol_inum inum,
	struct folio **fs, unsigned nr_folios)
	{
	u64 offset = folio_sector(fs[0]);
	bool need_set = false;

	for (unsigned folio_idx = 0; folio_idx < nr_folios; folio_idx++) {
	struct bch_folio *s = bch2_folio_create(fs[folio_idx], GFP_KERNEL);
	if (!s)
	return -ENOMEM;

	need_set \|= !s->uptodate;
	}

	if (!need_set)
	return 0;

	unsigned folio_idx = 0;

	return bch2_trans_run(c,
	for_each_btree_key_in_subvolume_upto(trans, iter, BTREE_ID_extents,
	POS(inum.inum, offset),
	POS(inum.inum, U64_MAX),
	inum.subvol, BTREE_ITER_slots, k, ({
	unsigned nr_ptrs = bch2_bkey_nr_ptrs_fully_allocated(k);
	unsigned state = bkey_to_sector_state(k);

	while (folio_idx < nr_folios) {
	struct folio *folio = fs[folio_idx];
	u64 folio_start = folio_sector(folio);
	u64 folio_end = folio_end_sector(folio);
	unsigned folio_offset = max(bkey_start_offset(k.k), folio_start) -
	folio_start;
	unsigned folio_len = min(k.k->p.offset, folio_end) -
	folio_offset - folio_start;

	BUG_ON(k.k->p.offset < folio_start);
	BUG_ON(bkey_start_offset(k.k) > folio_end);

	if (!bch2_folio(folio)->uptodate)
	__bch2_folio_set(folio, folio_offset, folio_len, nr_ptrs, state);

	if (k.k->p.offset < folio_end)
	break;
	folio_idx++;
	}

	if (folio_idx == nr_folios)
	break;
	0;
	})));
	}

	void bch2_bio_page_state_set(struct bio *bio, struct bkey_s_c k)
	{
	struct bvec_iter iter;
	struct folio_vec fv;
	unsigned nr_ptrs = k.k->type == KEY_TYPE_reflink_v
	? 0 : bch2_bkey_nr_ptrs_fully_allocated(k);
	unsigned state = bkey_to_sector_state(k);

	bio_for_each_folio(fv, bio, iter)
	__bch2_folio_set(fv.fv_folio,
	fv.fv_offset >> 9,
	fv.fv_len >> 9,
	nr_ptrs, state);
	}

	void bch2_mark_pagecache_unallocated(struct bch_inode_info *inode,
	u64 start, u64 end)
	{
	pgoff_t index = start >> PAGE_SECTORS_SHIFT;
	pgoff_t end_index = (end - 1) >> PAGE_SECTORS_SHIFT;
	struct folio_batch fbatch;
	unsigned i, j;

	if (end <= start)
	return;

	folio_batch_init(&fbatch);

	while (filemap_get_folios(inode->v.i_mapping,
	&index, end_index, &fbatch)) {
	for (i = 0; i < folio_batch_count(&fbatch); i++) {
	struct folio *folio = fbatch.folios[i];
	u64 folio_start = folio_sector(folio);
	u64 folio_end = folio_end_sector(folio);
	unsigned folio_offset = max(start, folio_start) - folio_start;
	unsigned folio_len = min(end, folio_end) - folio_offset - folio_start;
	struct bch_folio *s;

	BUG_ON(end <= folio_start);

	folio_lock(folio);
	s = bch2_folio(folio);

	if (s) {
	spin_lock(&s->lock);
	for (j = folio_offset; j < folio_offset + folio_len; j++)
	s->s[j].nr_replicas = 0;
	spin_unlock(&s->lock);
	}

	folio_unlock(folio);
	}
	folio_batch_release(&fbatch);
	cond_resched();
	}
	}

	int bch2_mark_pagecache_reserved(struct bch_inode_info *inode,
	u64 *start, u64 end,
	bool nonblocking)
	{
	struct bch_fs *c = inode->v.i_sb->s_fs_info;
	pgoff_t index = *start >> PAGE_SECTORS_SHIFT;
	pgoff_t end_index = (end - 1) >> PAGE_SECTORS_SHIFT;
	struct folio_batch fbatch;
	s64 i_sectors_delta = 0;
	int ret = 0;

	if (end <= *start)
	return 0;

	folio_batch_init(&fbatch);

	while (filemap_get_folios(inode->v.i_mapping,
	&index, end_index, &fbatch)) {
	for (unsigned i = 0; i < folio_batch_count(&fbatch); i++) {
	struct folio *folio = fbatch.folios[i];

	if (!nonblocking)
	folio_lock(folio);
	else if (!folio_trylock(folio)) {
	folio_batch_release(&fbatch);
	ret = -EAGAIN;
	break;
	}

	u64 folio_start = folio_sector(folio);
	u64 folio_end = folio_end_sector(folio);

	BUG_ON(end <= folio_start);

	*start = min(end, folio_end);

	struct bch_folio *s = bch2_folio(folio);
	if (s) {
	unsigned folio_offset = max(*start, folio_start) - folio_start;
	unsigned folio_len = min(end, folio_end) - folio_offset - folio_start;

	spin_lock(&s->lock);
	for (unsigned j = folio_offset; j < folio_offset + folio_len; j++) {
	i_sectors_delta -= s->s[j].state == SECTOR_dirty;
	bch2_folio_sector_set(folio, s, j,
	folio_sector_reserve(s->s[j].state));
	}
	spin_unlock(&s->lock);
	}

	folio_unlock(folio);
	}
	folio_batch_release(&fbatch);
	cond_resched();
	}

	bch2_i_sectors_acct(c, inode, NULL, i_sectors_delta);
	return ret;
	}

	static inline unsigned sectors_to_reserve(struct bch_folio_sector *s,
	unsigned nr_replicas)
	{
	return max(0, (int) nr_replicas -
	s->nr_replicas -
	s->replicas_reserved);
	}

	int bch2_get_folio_disk_reservation(struct bch_fs *c,
	struct bch_inode_info *inode,
	struct folio *folio, bool check_enospc)
	{
	struct bch_folio *s = bch2_folio_create(folio, 0);
	unsigned nr_replicas = inode_nr_replicas(c, inode);
	struct disk_reservation disk_res = { 0 };
	unsigned i, sectors = folio_sectors(folio), disk_res_sectors = 0;
	int ret;

	if (!s)
	return -ENOMEM;

	for (i = 0; i < sectors; i++)
	disk_res_sectors += sectors_to_reserve(&s->s[i], nr_replicas);

	if (!disk_res_sectors)
	return 0;

	ret = bch2_disk_reservation_get(c, &disk_res,
	disk_res_sectors, 1,
	!check_enospc
	? BCH_DISK_RESERVATION_NOFAIL
	: 0);
	if (unlikely(ret))
	return ret;

	for (i = 0; i < sectors; i++)
	s->s[i].replicas_reserved +=
	sectors_to_reserve(&s->s[i], nr_replicas);

	return 0;
	}

	void bch2_folio_reservation_put(struct bch_fs *c,
	struct bch_inode_info *inode,
	struct bch2_folio_reservation *res)
	{
	bch2_disk_reservation_put(c, &res->disk);
	bch2_quota_reservation_put(c, inode, &res->quota);
	}

	static int __bch2_folio_reservation_get(struct bch_fs *c,
	struct bch_inode_info *inode,
	struct folio *folio,
	struct bch2_folio_reservation *res,
	size_t offset, size_t len,
	bool partial)
	{
	struct bch_folio *s = bch2_folio_create(folio, 0);
	unsigned i, disk_sectors = 0, quota_sectors = 0;
	struct disk_reservation disk_res = {};
	size_t reserved = len;
	int ret;

	if (!s)
	return -ENOMEM;

	BUG_ON(!s->uptodate);

	for (i = round_down(offset, block_bytes(c)) >> 9;
	i < round_up(offset + len, block_bytes(c)) >> 9;
	i++) {
	disk_sectors += sectors_to_reserve(&s->s[i], res->disk.nr_replicas);
	quota_sectors += s->s[i].state == SECTOR_unallocated;
	}

	if (disk_sectors) {
	ret = bch2_disk_reservation_add(c, &disk_res, disk_sectors,
	partial ? BCH_DISK_RESERVATION_PARTIAL : 0);
	if (unlikely(ret))
	return ret;

	if (unlikely(disk_res.sectors != disk_sectors)) {
	disk_sectors = quota_sectors = 0;

	for (i = round_down(offset, block_bytes(c)) >> 9;
	i < round_up(offset + len, block_bytes(c)) >> 9;
	i++) {
	disk_sectors += sectors_to_reserve(&s->s[i], res->disk.nr_replicas);
	if (disk_sectors > disk_res.sectors) {
	/*
	* Make sure to get a reservation that's
	* aligned to the filesystem blocksize:
	*/
	unsigned reserved_offset = round_down(i << 9, block_bytes(c));
	reserved = clamp(reserved_offset, offset, offset + len) - offset;

	if (!reserved) {
	bch2_disk_reservation_put(c, &disk_res);
	return -BCH_ERR_ENOSPC_disk_reservation;
	}
	break;
	}
	quota_sectors += s->s[i].state == SECTOR_unallocated;
	}
	}
	}

	if (quota_sectors) {
	ret = bch2_quota_reservation_add(c, inode, &res->quota, quota_sectors, true);
	if (unlikely(ret)) {
	bch2_disk_reservation_put(c, &disk_res);
	return ret;
	}
	}

	res->disk.sectors += disk_res.sectors;
	return partial ? reserved : 0;
	}

	int bch2_folio_reservation_get(struct bch_fs *c,
	struct bch_inode_info *inode,
	struct folio *folio,
	struct bch2_folio_reservation *res,
	size_t offset, size_t len)
	{
	return __bch2_folio_reservation_get(c, inode, folio, res, offset, len, false);
	}

	ssize_t bch2_folio_reservation_get_partial(struct bch_fs *c,
	struct bch_inode_info *inode,
	struct folio *folio,
	struct bch2_folio_reservation *res,
	size_t offset, size_t len)
	{
	return __bch2_folio_reservation_get(c, inode, folio, res, offset, len, true);
	}

	static void bch2_clear_folio_bits(struct folio *folio)
	{
	struct bch_inode_info *inode = to_bch_ei(folio->mapping->host);
	struct bch_fs *c = inode->v.i_sb->s_fs_info;
	struct bch_folio *s = bch2_folio(folio);
	struct disk_reservation disk_res = { 0 };
	int i, sectors = folio_sectors(folio), dirty_sectors = 0;

	if (!s)
	return;

	EBUG_ON(!folio_test_locked(folio));
	EBUG_ON(folio_test_writeback(folio));

	for (i = 0; i < sectors; i++) {
	disk_res.sectors += s->s[i].replicas_reserved;
	s->s[i].replicas_reserved = 0;

	dirty_sectors -= s->s[i].state == SECTOR_dirty;
	bch2_folio_sector_set(folio, s, i, folio_sector_undirty(s->s[i].state));
	}

	bch2_disk_reservation_put(c, &disk_res);

	bch2_i_sectors_acct(c, inode, NULL, dirty_sectors);

	bch2_folio_release(folio);
	}

	void bch2_set_folio_dirty(struct bch_fs *c,
	struct bch_inode_info *inode,
	struct folio *folio,
	struct bch2_folio_reservation *res,
	unsigned offset, unsigned len)
	{
	struct bch_folio *s = bch2_folio(folio);
	unsigned i, dirty_sectors = 0;

	WARN_ON((u64) folio_pos(folio) + offset + len >
	round_up((u64) i_size_read(&inode->v), block_bytes(c)));

	BUG_ON(!s->uptodate);

	spin_lock(&s->lock);

	for (i = round_down(offset, block_bytes(c)) >> 9;
	i < round_up(offset + len, block_bytes(c)) >> 9;
	i++) {
	unsigned sectors = sectors_to_reserve(&s->s[i],
	res->disk.nr_replicas);

	/*
	* This can happen if we race with the error path in
	* bch2_writepage_io_done():
	*/
	sectors = min_t(unsigned, sectors, res->disk.sectors);

	s->s[i].replicas_reserved += sectors;
	res->disk.sectors -= sectors;

	dirty_sectors += s->s[i].state == SECTOR_unallocated;

	bch2_folio_sector_set(folio, s, i, folio_sector_dirty(s->s[i].state));
	}

	spin_unlock(&s->lock);

	bch2_i_sectors_acct(c, inode, &res->quota, dirty_sectors);

	if (!folio_test_dirty(folio))
	filemap_dirty_folio(inode->v.i_mapping, folio);
	}

	vm_fault_t bch2_page_fault(struct vm_fault *vmf)
	{
	struct file *file = vmf->vma->vm_file;
	struct address_space *mapping = file->f_mapping;
	struct address_space *fdm = faults_disabled_mapping();
	struct bch_inode_info *inode = file_bch_inode(file);
	vm_fault_t ret;

	if (fdm == mapping)
	return VM_FAULT_SIGBUS;

	/* Lock ordering: */
	if (fdm > mapping) {
	struct bch_inode_info *fdm_host = to_bch_ei(fdm->host);

	if (bch2_pagecache_add_tryget(inode))
	goto got_lock;

	bch2_pagecache_block_put(fdm_host);

	bch2_pagecache_add_get(inode);
	bch2_pagecache_add_put(inode);

	bch2_pagecache_block_get(fdm_host);

	/* Signal that lock has been dropped: */
	set_fdm_dropped_locks();
	return VM_FAULT_SIGBUS;
	}

	bch2_pagecache_add_get(inode);
	got_lock:
	ret = filemap_fault(vmf);
	bch2_pagecache_add_put(inode);

	return ret;
	}

	vm_fault_t bch2_page_mkwrite(struct vm_fault *vmf)
	{
	struct folio *folio = page_folio(vmf->page);
	struct file *file = vmf->vma->vm_file;
	struct bch_inode_info *inode = file_bch_inode(file);
	struct address_space *mapping = file->f_mapping;
	struct bch_fs *c = inode->v.i_sb->s_fs_info;
	struct bch2_folio_reservation res;
	unsigned len;
	loff_t isize;
	vm_fault_t ret;

	bch2_folio_reservation_init(c, inode, &res);

	sb_start_pagefault(inode->v.i_sb);
	file_update_time(file);

	/*
	* Not strictly necessary, but helps avoid dio writes livelocking in
	* bch2_write_invalidate_inode_pages_range() - can drop this if/when we get
	* a bch2_write_invalidate_inode_pages_range() that works without dropping
	* page lock before invalidating page
	*/
	bch2_pagecache_add_get(inode);

	folio_lock(folio);
	isize = i_size_read(&inode->v);

	if (folio->mapping != mapping \|\| folio_pos(folio) >= isize) {
	folio_unlock(folio);
	ret = VM_FAULT_NOPAGE;
	goto out;
	}

	len = min_t(loff_t, folio_size(folio), isize - folio_pos(folio));

	if (bch2_folio_set(c, inode_inum(inode), &folio, 1) ?:
	bch2_folio_reservation_get(c, inode, folio, &res, 0, len)) {
	folio_unlock(folio);
	ret = VM_FAULT_SIGBUS;
	goto out;
	}

	bch2_set_folio_dirty(c, inode, folio, &res, 0, len);
	bch2_folio_reservation_put(c, inode, &res);

	folio_wait_stable(folio);
	ret = VM_FAULT_LOCKED;
	out:
	bch2_pagecache_add_put(inode);
	sb_end_pagefault(inode->v.i_sb);

	return ret;
	}

	void bch2_invalidate_folio(struct folio *folio, size_t offset, size_t length)
	{
	if (offset \|\| length < folio_size(folio))
	return;

	bch2_clear_folio_bits(folio);
	}

	bool bch2_release_folio(struct folio *folio, gfp_t gfp_mask)
	{
	if (folio_test_dirty(folio) \|\| folio_test_writeback(folio))
	return false;

	bch2_clear_folio_bits(folio);
	return true;
	}

	/* fseek: */

	static int folio_data_offset(struct folio *folio, loff_t pos,
	unsigned min_replicas)
	{
	struct bch_folio *s = bch2_folio(folio);
	unsigned i, sectors = folio_sectors(folio);

	if (s)
	for (i = folio_pos_to_s(folio, pos); i < sectors; i++)
	if (s->s[i].state >= SECTOR_dirty &&
	s->s[i].nr_replicas + s->s[i].replicas_reserved >= min_replicas)
	return i << SECTOR_SHIFT;

	return -1;
	}

	loff_t bch2_seek_pagecache_data(struct inode *vinode,
	loff_t start_offset,
	loff_t end_offset,
	unsigned min_replicas,
	bool nonblock)
	{
	struct folio_batch fbatch;
	pgoff_t start_index = start_offset >> PAGE_SHIFT;
	pgoff_t end_index = end_offset >> PAGE_SHIFT;
	pgoff_t index = start_index;
	unsigned i;
	loff_t ret;
	int offset;

	folio_batch_init(&fbatch);

	while (filemap_get_folios(vinode->i_mapping,
	&index, end_index, &fbatch)) {
	for (i = 0; i < folio_batch_count(&fbatch); i++) {
	struct folio *folio = fbatch.folios[i];

	if (!nonblock) {
	folio_lock(folio);
	} else if (!folio_trylock(folio)) {
	folio_batch_release(&fbatch);
	return -EAGAIN;
	}

	offset = folio_data_offset(folio,
	max(folio_pos(folio), start_offset),
	min_replicas);
	if (offset >= 0) {
	ret = clamp(folio_pos(folio) + offset,
	start_offset, end_offset);
	folio_unlock(folio);
	folio_batch_release(&fbatch);
	return ret;
	}
	folio_unlock(folio);
	}
	folio_batch_release(&fbatch);
	cond_resched();
	}

	return end_offset;
	}

	/*
	* Search for a hole in a folio.
	*
	* The filemap layer returns -ENOENT if no folio exists, so reuse the same error
	* code to indicate a pagecache hole exists at the returned offset. Otherwise
	* return 0 if the folio is filled with data, or an error code. This function
	* can return -EAGAIN if nonblock is specified.
	*/
	static int folio_hole_offset(struct address_space mapping, loff_t offset,
	unsigned min_replicas, bool nonblock)
	{
	struct folio *folio;
	struct bch_folio *s;
	unsigned i, sectors;
	int ret = -ENOENT;

	folio = __filemap_get_folio(mapping, *offset >> PAGE_SHIFT,
	FGP_LOCK\|(nonblock ? FGP_NOWAIT : 0), 0);
	if (IS_ERR(folio))
	return PTR_ERR(folio);

	s = bch2_folio(folio);
	if (!s)
	goto unlock;

	sectors = folio_sectors(folio);
	for (i = folio_pos_to_s(folio, *offset); i < sectors; i++)
	if (s->s[i].state < SECTOR_dirty \|\|
	s->s[i].nr_replicas + s->s[i].replicas_reserved < min_replicas) {
	offset = max(offset,
	folio_pos(folio) + (i << SECTOR_SHIFT));
	goto unlock;
	}

	*offset = folio_end_pos(folio);
	ret = 0;
	unlock:
	folio_unlock(folio);
	folio_put(folio);
	return ret;
	}

	loff_t bch2_seek_pagecache_hole(struct inode *vinode,
	loff_t start_offset,
	loff_t end_offset,
	unsigned min_replicas,
	bool nonblock)
	{
	struct address_space *mapping = vinode->i_mapping;
	loff_t offset = start_offset;
	loff_t ret = 0;

	while (!ret && offset < end_offset)
	ret = folio_hole_offset(mapping, &offset, min_replicas, nonblock);

	if (ret && ret != -ENOENT)
	return ret;
	return min(offset, end_offset);
	}

	int bch2_clamp_data_hole(struct inode *inode,
	u64 *hole_start,
	u64 *hole_end,
	unsigned min_replicas,
	bool nonblock)
	{
	loff_t ret;

	ret = bch2_seek_pagecache_hole(inode,
	hole_start << 9, hole_end << 9, min_replicas, nonblock) >> 9;
	if (ret < 0)
	return ret;

	*hole_start = ret;

	if (hole_start == hole_end)
	return 0;

	ret = bch2_seek_pagecache_data(inode,
	hole_start << 9, hole_end << 9, min_replicas, nonblock) >> 9;
	if (ret < 0)
	return ret;

	*hole_end = ret;
	return 0;
	}

	#endif /* NO_BCACHEFS_FS */