drm/panthor: Don't add write fences to the shared BOs

[drm/drm-misc.git] / fs / btrfs / subpage.c

// SPDX-License-Identifier: GPL-2.0

#include <linux/slab.h>
#include "messages.h"
#include "ctree.h"
#include "subpage.h"
#include "btrfs_inode.h"

/*
 * Subpage (sectorsize < PAGE_SIZE) support overview:
 *
 * Limitations:
 *
 * - Only support 64K page size for now
 *   This is to make metadata handling easier, as 64K page would ensure
 *   all nodesize would fit inside one page, thus we don't need to handle
 *   cases where a tree block crosses several pages.
 *
 * - Only metadata read-write for now
 *   The data read-write part is in development.
 *
 * - Metadata can't cross 64K page boundary
 *   btrfs-progs and kernel have done that for a while, thus only ancient
 *   filesystems could have such problem.  For such case, do a graceful
 *   rejection.
 *
 * Special behavior:
 *
 * - Metadata
 *   Metadata read is fully supported.
 *   Meaning when reading one tree block will only trigger the read for the
 *   needed range, other unrelated range in the same page will not be touched.
 *
 *   Metadata write support is partial.
 *   The writeback is still for the full page, but we will only submit
 *   the dirty extent buffers in the page.
 *
 *   This means, if we have a metadata page like this:
 *
 *   Page offset
 *   0         16K         32K         48K        64K
 *   |/////////|           |///////////|
 *        \- Tree block A        \- Tree block B
 *
 *   Even if we just want to writeback tree block A, we will also writeback
 *   tree block B if it's also dirty.
 *
 *   This may cause extra metadata writeback which results more COW.
 *
 * Implementation:
 *
 * - Common
 *   Both metadata and data will use a new structure, btrfs_subpage, to
 *   record the status of each sector inside a page.  This provides the extra
 *   granularity needed.
 *
 * - Metadata
 *   Since we have multiple tree blocks inside one page, we can't rely on page
 *   locking anymore, or we will have greatly reduced concurrency or even
 *   deadlocks (hold one tree lock while trying to lock another tree lock in
 *   the same page).
 *
 *   Thus for metadata locking, subpage support relies on io_tree locking only.
 *   This means a slightly higher tree locking latency.
 */

#if PAGE_SIZE > SZ_4K
bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct address_space *mapping)
{
        if (fs_info->sectorsize >= PAGE_SIZE)
                return false;

        /*
         * Only data pages (either through DIO or compression) can have no
         * mapping. And if page->mapping->host is data inode, it's subpage.
         * As we have ruled our sectorsize >= PAGE_SIZE case already.
         */
        if (!mapping || !mapping->host || is_data_inode(BTRFS_I(mapping->host)))
                return true;

        /*
         * Now the only remaining case is metadata, which we only go subpage
         * routine if nodesize < PAGE_SIZE.
         */
        if (fs_info->nodesize < PAGE_SIZE)
                return true;
        return false;
}
#endif

int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
                         struct folio *folio, enum btrfs_subpage_type type)
{
        struct btrfs_subpage *subpage;

        /*
         * We have cases like a dummy extent buffer page, which is not mapped
         * and doesn't need to be locked.
         */
        if (folio->mapping)
                ASSERT(folio_test_locked(folio));

        /* Either not subpage, or the folio already has private attached. */
        if (!btrfs_is_subpage(fs_info, folio->mapping) || folio_test_private(folio))
                return 0;

        subpage = btrfs_alloc_subpage(fs_info, type);
        if (IS_ERR(subpage))
                return  PTR_ERR(subpage);

        folio_attach_private(folio, subpage);
        return 0;
}

void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info, struct folio *folio)
{
        struct btrfs_subpage *subpage;

        /* Either not subpage, or the folio already has private attached. */
        if (!btrfs_is_subpage(fs_info, folio->mapping) || !folio_test_private(folio))
                return;

        subpage = folio_detach_private(folio);
        ASSERT(subpage);
        btrfs_free_subpage(subpage);
}

struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
                                          enum btrfs_subpage_type type)
{
        struct btrfs_subpage *ret;
        unsigned int real_size;

        ASSERT(fs_info->sectorsize < PAGE_SIZE);

        real_size = struct_size(ret, bitmaps,
                        BITS_TO_LONGS(btrfs_bitmap_nr_max * fs_info->sectors_per_page));
        ret = kzalloc(real_size, GFP_NOFS);
        if (!ret)
                return ERR_PTR(-ENOMEM);

        spin_lock_init(&ret->lock);
        if (type == BTRFS_SUBPAGE_METADATA) {
                atomic_set(&ret->eb_refs, 0);
        } else {
                atomic_set(&ret->readers, 0);
                atomic_set(&ret->writers, 0);
        }
        return ret;
}

void btrfs_free_subpage(struct btrfs_subpage *subpage)
{
        kfree(subpage);
}

/*
 * Increase the eb_refs of current subpage.
 *
 * This is important for eb allocation, to prevent race with last eb freeing
 * of the same page.
 * With the eb_refs increased before the eb inserted into radix tree,
 * detach_extent_buffer_page() won't detach the folio private while we're still
 * allocating the extent buffer.
 */
void btrfs_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio)
{
        struct btrfs_subpage *subpage;

        if (!btrfs_is_subpage(fs_info, folio->mapping))
                return;

        ASSERT(folio_test_private(folio) && folio->mapping);
        lockdep_assert_held(&folio->mapping->i_private_lock);

        subpage = folio_get_private(folio);
        atomic_inc(&subpage->eb_refs);
}

void btrfs_folio_dec_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio)
{
        struct btrfs_subpage *subpage;

        if (!btrfs_is_subpage(fs_info, folio->mapping))
                return;

        ASSERT(folio_test_private(folio) && folio->mapping);
        lockdep_assert_held(&folio->mapping->i_private_lock);

        subpage = folio_get_private(folio);
        ASSERT(atomic_read(&subpage->eb_refs));
        atomic_dec(&subpage->eb_refs);
}

static void btrfs_subpage_assert(const struct btrfs_fs_info *fs_info,
                                 struct folio *folio, u64 start, u32 len)
{
        /* For subpage support, the folio must be single page. */
        ASSERT(folio_order(folio) == 0);

        /* Basic checks */
        ASSERT(folio_test_private(folio) && folio_get_private(folio));
        ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
               IS_ALIGNED(len, fs_info->sectorsize));
        /*
         * The range check only works for mapped page, we can still have
         * unmapped page like dummy extent buffer pages.
         */
        if (folio->mapping)
                ASSERT(folio_pos(folio) <= start &&
                       start + len <= folio_pos(folio) + PAGE_SIZE);
}

#define subpage_calc_start_bit(fs_info, folio, name, start, len)        \
({                                                                      \
        unsigned int __start_bit;                                               \
                                                                        \
        btrfs_subpage_assert(fs_info, folio, start, len);               \
        __start_bit = offset_in_page(start) >> fs_info->sectorsize_bits; \
        __start_bit += fs_info->sectors_per_page * btrfs_bitmap_nr_##name; \
        __start_bit;                                                    \
})

void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
                                struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        const int start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len);
        const int nbits = len >> fs_info->sectorsize_bits;
        unsigned long flags;


        btrfs_subpage_assert(fs_info, folio, start, len);

        spin_lock_irqsave(&subpage->lock, flags);
        /*
         * Even though it's just for reading the page, no one should have
         * locked the subpage range.
         */
        ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
        bitmap_set(subpage->bitmaps, start_bit, nbits);
        atomic_add(nbits, &subpage->readers);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
                              struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        const int start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len);
        const int nbits = len >> fs_info->sectorsize_bits;
        unsigned long flags;
        bool is_data;
        bool last;

        btrfs_subpage_assert(fs_info, folio, start, len);
        is_data = is_data_inode(BTRFS_I(folio->mapping->host));

        spin_lock_irqsave(&subpage->lock, flags);

        /* The range should have already been locked. */
        ASSERT(bitmap_test_range_all_set(subpage->bitmaps, start_bit, nbits));
        ASSERT(atomic_read(&subpage->readers) >= nbits);

        bitmap_clear(subpage->bitmaps, start_bit, nbits);
        last = atomic_sub_and_test(nbits, &subpage->readers);

        /*
         * For data we need to unlock the page if the last read has finished.
         *
         * And please don't replace @last with atomic_sub_and_test() call
         * inside if () condition.
         * As we want the atomic_sub_and_test() to be always executed.
         */
        if (is_data && last)
                folio_unlock(folio);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

static void btrfs_subpage_clamp_range(struct folio *folio, u64 *start, u32 *len)
{
        u64 orig_start = *start;
        u32 orig_len = *len;

        *start = max_t(u64, folio_pos(folio), orig_start);
        /*
         * For certain call sites like btrfs_drop_pages(), we may have pages
         * beyond the target range. In that case, just set @len to 0, subpage
         * helpers can handle @len == 0 without any problem.
         */
        if (folio_pos(folio) >= orig_start + orig_len)
                *len = 0;
        else
                *len = min_t(u64, folio_pos(folio) + PAGE_SIZE,
                             orig_start + orig_len) - *start;
}

static void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
                                       struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        const int start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len);
        const int nbits = (len >> fs_info->sectorsize_bits);
        unsigned long flags;
        int ret;

        btrfs_subpage_assert(fs_info, folio, start, len);

        spin_lock_irqsave(&subpage->lock, flags);
        ASSERT(atomic_read(&subpage->readers) == 0);
        ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
        bitmap_set(subpage->bitmaps, start_bit, nbits);
        ret = atomic_add_return(nbits, &subpage->writers);
        ASSERT(ret == nbits);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

static bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
                                              struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        const int start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len);
        const int nbits = (len >> fs_info->sectorsize_bits);
        unsigned long flags;
        unsigned int cleared = 0;
        int bit = start_bit;
        bool last;

        btrfs_subpage_assert(fs_info, folio, start, len);

        spin_lock_irqsave(&subpage->lock, flags);
        /*
         * We have call sites passing @lock_page into
         * extent_clear_unlock_delalloc() for compression path.
         *
         * This @locked_page is locked by plain lock_page(), thus its
         * subpage::writers is 0.  Handle them in a special way.
         */
        if (atomic_read(&subpage->writers) == 0) {
                spin_unlock_irqrestore(&subpage->lock, flags);
                return true;
        }

        for_each_set_bit_from(bit, subpage->bitmaps, start_bit + nbits) {
                clear_bit(bit, subpage->bitmaps);
                cleared++;
        }
        ASSERT(atomic_read(&subpage->writers) >= cleared);
        last = atomic_sub_and_test(cleared, &subpage->writers);
        spin_unlock_irqrestore(&subpage->lock, flags);
        return last;
}

/*
 * Lock a folio for delalloc page writeback.
 *
 * Return -EAGAIN if the page is not properly initialized.
 * Return 0 with the page locked, and writer counter updated.
 *
 * Even with 0 returned, the page still need extra check to make sure
 * it's really the correct page, as the caller is using
 * filemap_get_folios_contig(), which can race with page invalidating.
 */
int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info,
                                  struct folio *folio, u64 start, u32 len)
{
        if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping)) {
                folio_lock(folio);
                return 0;
        }
        folio_lock(folio);
        if (!folio_test_private(folio) || !folio_get_private(folio)) {
                folio_unlock(folio);
                return -EAGAIN;
        }
        btrfs_subpage_clamp_range(folio, &start, &len);
        btrfs_subpage_start_writer(fs_info, folio, start, len);
        return 0;
}

/*
 * Handle different locked folios:
 *
 * - Non-subpage folio
 *   Just unlock it.
 *
 * - folio locked but without any subpage locked
 *   This happens either before writepage_delalloc() or the delalloc range is
 *   already handled by previous folio.
 *   We can simple unlock it.
 *
 * - folio locked with subpage range locked.
 *   We go through the locked sectors inside the range and clear their locked
 *   bitmap, reduce the writer lock number, and unlock the page if that's
 *   the last locked range.
 */
void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
                                 struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);

        ASSERT(folio_test_locked(folio));

        if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping)) {
                folio_unlock(folio);
                return;
        }

        /*
         * For subpage case, there are two types of locked page.  With or
         * without writers number.
         *
         * Since we own the page lock, no one else could touch subpage::writers
         * and we are safe to do several atomic operations without spinlock.
         */
        if (atomic_read(&subpage->writers) == 0) {
                /* No writers, locked by plain lock_page(). */
                folio_unlock(folio);
                return;
        }

        btrfs_subpage_clamp_range(folio, &start, &len);
        if (btrfs_subpage_end_and_test_writer(fs_info, folio, start, len))
                folio_unlock(folio);
}

void btrfs_folio_end_writer_lock_bitmap(const struct btrfs_fs_info *fs_info,
                                        struct folio *folio, unsigned long bitmap)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        const int start_bit = fs_info->sectors_per_page * btrfs_bitmap_nr_locked;
        unsigned long flags;
        bool last = false;
        int cleared = 0;
        int bit;

        if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping)) {
                folio_unlock(folio);
                return;
        }

        if (atomic_read(&subpage->writers) == 0) {
                /* No writers, locked by plain lock_page(). */
                folio_unlock(folio);
                return;
        }

        spin_lock_irqsave(&subpage->lock, flags);
        for_each_set_bit(bit, &bitmap, fs_info->sectors_per_page) {
                if (test_and_clear_bit(bit + start_bit, subpage->bitmaps))
                        cleared++;
        }
        ASSERT(atomic_read(&subpage->writers) >= cleared);
        last = atomic_sub_and_test(cleared, &subpage->writers);
        spin_unlock_irqrestore(&subpage->lock, flags);
        if (last)
                folio_unlock(folio);
}

#define subpage_test_bitmap_all_set(fs_info, subpage, name)             \
        bitmap_test_range_all_set(subpage->bitmaps,                     \
                        fs_info->sectors_per_page * btrfs_bitmap_nr_##name, \
                        fs_info->sectors_per_page)

#define subpage_test_bitmap_all_zero(fs_info, subpage, name)            \
        bitmap_test_range_all_zero(subpage->bitmaps,                    \
                        fs_info->sectors_per_page * btrfs_bitmap_nr_##name, \
                        fs_info->sectors_per_page)

void btrfs_subpage_set_uptodate(const struct btrfs_fs_info *fs_info,
                                struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        uptodate, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        if (subpage_test_bitmap_all_set(fs_info, subpage, uptodate))
                folio_mark_uptodate(folio);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

void btrfs_subpage_clear_uptodate(const struct btrfs_fs_info *fs_info,
                                  struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        uptodate, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        folio_clear_uptodate(folio);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

void btrfs_subpage_set_dirty(const struct btrfs_fs_info *fs_info,
                             struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        dirty, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        spin_unlock_irqrestore(&subpage->lock, flags);
        folio_mark_dirty(folio);
}

/*
 * Extra clear_and_test function for subpage dirty bitmap.
 *
 * Return true if we're the last bits in the dirty_bitmap and clear the
 * dirty_bitmap.
 * Return false otherwise.
 *
 * NOTE: Callers should manually clear page dirty for true case, as we have
 * extra handling for tree blocks.
 */
bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
                                        struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        dirty, start, len);
        unsigned long flags;
        bool last = false;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        if (subpage_test_bitmap_all_zero(fs_info, subpage, dirty))
                last = true;
        spin_unlock_irqrestore(&subpage->lock, flags);
        return last;
}

void btrfs_subpage_clear_dirty(const struct btrfs_fs_info *fs_info,
                               struct folio *folio, u64 start, u32 len)
{
        bool last;

        last = btrfs_subpage_clear_and_test_dirty(fs_info, folio, start, len);
        if (last)
                folio_clear_dirty_for_io(folio);
}

void btrfs_subpage_set_writeback(const struct btrfs_fs_info *fs_info,
                                 struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        writeback, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        if (!folio_test_writeback(folio))
                folio_start_writeback(folio);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

void btrfs_subpage_clear_writeback(const struct btrfs_fs_info *fs_info,
                                   struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        writeback, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        if (subpage_test_bitmap_all_zero(fs_info, subpage, writeback)) {
                ASSERT(folio_test_writeback(folio));
                folio_end_writeback(folio);
        }
        spin_unlock_irqrestore(&subpage->lock, flags);
}

void btrfs_subpage_set_ordered(const struct btrfs_fs_info *fs_info,
                               struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        ordered, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        folio_set_ordered(folio);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

void btrfs_subpage_clear_ordered(const struct btrfs_fs_info *fs_info,
                                 struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        ordered, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        if (subpage_test_bitmap_all_zero(fs_info, subpage, ordered))
                folio_clear_ordered(folio);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

void btrfs_subpage_set_checked(const struct btrfs_fs_info *fs_info,
                               struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        checked, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        if (subpage_test_bitmap_all_set(fs_info, subpage, checked))
                folio_set_checked(folio);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

void btrfs_subpage_clear_checked(const struct btrfs_fs_info *fs_info,
                                 struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                        checked, start, len);
        unsigned long flags;

        spin_lock_irqsave(&subpage->lock, flags);
        bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
        folio_clear_checked(folio);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

/*
 * Unlike set/clear which is dependent on each page status, for test all bits
 * are tested in the same way.
 */
#define IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(name)                           \
bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,     \
                               struct folio *folio, u64 start, u32 len) \
{                                                                       \
        struct btrfs_subpage *subpage = folio_get_private(folio);       \
        unsigned int start_bit = subpage_calc_start_bit(fs_info, folio, \
                                                name, start, len);      \
        unsigned long flags;                                            \
        bool ret;                                                       \
                                                                        \
        spin_lock_irqsave(&subpage->lock, flags);                       \
        ret = bitmap_test_range_all_set(subpage->bitmaps, start_bit,    \
                                len >> fs_info->sectorsize_bits);       \
        spin_unlock_irqrestore(&subpage->lock, flags);                  \
        return ret;                                                     \
}
IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(uptodate);
IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(dirty);
IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(writeback);
IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(ordered);
IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(checked);

/*
 * Note that, in selftests (extent-io-tests), we can have empty fs_info passed
 * in.  We only test sectorsize == PAGE_SIZE cases so far, thus we can fall
 * back to regular sectorsize branch.
 */
#define IMPLEMENT_BTRFS_PAGE_OPS(name, folio_set_func,                  \
                                 folio_clear_func, folio_test_func)     \
void btrfs_folio_set_##name(const struct btrfs_fs_info *fs_info,        \
                            struct folio *folio, u64 start, u32 len)    \
{                                                                       \
        if (unlikely(!fs_info) ||                                       \
            !btrfs_is_subpage(fs_info, folio->mapping)) {               \
                folio_set_func(folio);                                  \
                return;                                                 \
        }                                                               \
        btrfs_subpage_set_##name(fs_info, folio, start, len);           \
}                                                                       \
void btrfs_folio_clear_##name(const struct btrfs_fs_info *fs_info,      \
                              struct folio *folio, u64 start, u32 len)  \
{                                                                       \
        if (unlikely(!fs_info) ||                                       \
            !btrfs_is_subpage(fs_info, folio->mapping)) {               \
                folio_clear_func(folio);                                \
                return;                                                 \
        }                                                               \
        btrfs_subpage_clear_##name(fs_info, folio, start, len);         \
}                                                                       \
bool btrfs_folio_test_##name(const struct btrfs_fs_info *fs_info,       \
                             struct folio *folio, u64 start, u32 len)   \
{                                                                       \
        if (unlikely(!fs_info) ||                                       \
            !btrfs_is_subpage(fs_info, folio->mapping))                 \
                return folio_test_func(folio);                          \
        return btrfs_subpage_test_##name(fs_info, folio, start, len);   \
}                                                                       \
void btrfs_folio_clamp_set_##name(const struct btrfs_fs_info *fs_info,  \
                                  struct folio *folio, u64 start, u32 len) \
{                                                                       \
        if (unlikely(!fs_info) ||                                       \
            !btrfs_is_subpage(fs_info, folio->mapping)) {               \
                folio_set_func(folio);                                  \
                return;                                                 \
        }                                                               \
        btrfs_subpage_clamp_range(folio, &start, &len);                 \
        btrfs_subpage_set_##name(fs_info, folio, start, len);           \
}                                                                       \
void btrfs_folio_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
                                    struct folio *folio, u64 start, u32 len) \
{                                                                       \
        if (unlikely(!fs_info) ||                                       \
            !btrfs_is_subpage(fs_info, folio->mapping)) {               \
                folio_clear_func(folio);                                \
                return;                                                 \
        }                                                               \
        btrfs_subpage_clamp_range(folio, &start, &len);                 \
        btrfs_subpage_clear_##name(fs_info, folio, start, len);         \
}                                                                       \
bool btrfs_folio_clamp_test_##name(const struct btrfs_fs_info *fs_info, \
                                   struct folio *folio, u64 start, u32 len) \
{                                                                       \
        if (unlikely(!fs_info) ||                                       \
            !btrfs_is_subpage(fs_info, folio->mapping))                 \
                return folio_test_func(folio);                          \
        btrfs_subpage_clamp_range(folio, &start, &len);                 \
        return btrfs_subpage_test_##name(fs_info, folio, start, len);   \
}
IMPLEMENT_BTRFS_PAGE_OPS(uptodate, folio_mark_uptodate, folio_clear_uptodate,
                         folio_test_uptodate);
IMPLEMENT_BTRFS_PAGE_OPS(dirty, folio_mark_dirty, folio_clear_dirty_for_io,
                         folio_test_dirty);
IMPLEMENT_BTRFS_PAGE_OPS(writeback, folio_start_writeback, folio_end_writeback,
                         folio_test_writeback);
IMPLEMENT_BTRFS_PAGE_OPS(ordered, folio_set_ordered, folio_clear_ordered,
                         folio_test_ordered);
IMPLEMENT_BTRFS_PAGE_OPS(checked, folio_set_checked, folio_clear_checked,
                         folio_test_checked);

/*
 * Make sure not only the page dirty bit is cleared, but also subpage dirty bit
 * is cleared.
 */
void btrfs_folio_assert_not_dirty(const struct btrfs_fs_info *fs_info,
                                  struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage;
        unsigned int start_bit;
        unsigned int nbits;
        unsigned long flags;

        if (!IS_ENABLED(CONFIG_BTRFS_ASSERT))
                return;

        if (!btrfs_is_subpage(fs_info, folio->mapping)) {
                ASSERT(!folio_test_dirty(folio));
                return;
        }

        start_bit = subpage_calc_start_bit(fs_info, folio, dirty, start, len);
        nbits = len >> fs_info->sectorsize_bits;
        subpage = folio_get_private(folio);
        ASSERT(subpage);
        spin_lock_irqsave(&subpage->lock, flags);
        ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
        spin_unlock_irqrestore(&subpage->lock, flags);
}

/*
 * This is for folio already locked by plain lock_page()/folio_lock(), which
 * doesn't have any subpage awareness.
 *
 * This populates the involved subpage ranges so that subpage helpers can
 * properly unlock them.
 */
void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
                                 struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage;
        unsigned long flags;
        unsigned int start_bit;
        unsigned int nbits;
        int ret;

        ASSERT(folio_test_locked(folio));
        if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping))
                return;

        subpage = folio_get_private(folio);
        start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len);
        nbits = len >> fs_info->sectorsize_bits;
        spin_lock_irqsave(&subpage->lock, flags);
        /* Target range should not yet be locked. */
        ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
        bitmap_set(subpage->bitmaps, start_bit, nbits);
        ret = atomic_add_return(nbits, &subpage->writers);
        ASSERT(ret <= fs_info->sectors_per_page);
        spin_unlock_irqrestore(&subpage->lock, flags);
}

/*
 * Find any subpage writer locked range inside @folio, starting at file offset
 * @search_start. The caller should ensure the folio is locked.
 *
 * Return true and update @found_start_ret and @found_len_ret to the first
 * writer locked range.
 * Return false if there is no writer locked range.
 */
bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
                                      struct folio *folio, u64 search_start,
                                      u64 *found_start_ret, u32 *found_len_ret)
{
        struct btrfs_subpage *subpage = folio_get_private(folio);
        const u32 sectors_per_page = fs_info->sectors_per_page;
        const unsigned int len = PAGE_SIZE - offset_in_page(search_start);
        const unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
                                                locked, search_start, len);
        const unsigned int locked_bitmap_start = sectors_per_page * btrfs_bitmap_nr_locked;
        const unsigned int locked_bitmap_end = locked_bitmap_start + sectors_per_page;
        unsigned long flags;
        int first_zero;
        int first_set;
        bool found = false;

        ASSERT(folio_test_locked(folio));
        spin_lock_irqsave(&subpage->lock, flags);
        first_set = find_next_bit(subpage->bitmaps, locked_bitmap_end, start_bit);
        if (first_set >= locked_bitmap_end)
                goto out;

        found = true;

        *found_start_ret = folio_pos(folio) +
                ((first_set - locked_bitmap_start) << fs_info->sectorsize_bits);
        /*
         * Since @first_set is ensured to be smaller than locked_bitmap_end
         * here, @found_start_ret should be inside the folio.
         */
        ASSERT(*found_start_ret < folio_pos(folio) + PAGE_SIZE);

        first_zero = find_next_zero_bit(subpage->bitmaps, locked_bitmap_end, first_set);
        *found_len_ret = (first_zero - first_set) << fs_info->sectorsize_bits;
out:
        spin_unlock_irqrestore(&subpage->lock, flags);
        return found;
}

#define GET_SUBPAGE_BITMAP(subpage, fs_info, name, dst)                 \
{                                                                       \
        const int sectors_per_page = fs_info->sectors_per_page;         \
                                                                        \
        ASSERT(sectors_per_page < BITS_PER_LONG);                       \
        *dst = bitmap_read(subpage->bitmaps,                            \
                           sectors_per_page * btrfs_bitmap_nr_##name,   \
                           sectors_per_page);                           \
}

void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
                                      struct folio *folio, u64 start, u32 len)
{
        struct btrfs_subpage *subpage;
        const u32 sectors_per_page = fs_info->sectors_per_page;
        unsigned long uptodate_bitmap;
        unsigned long dirty_bitmap;
        unsigned long writeback_bitmap;
        unsigned long ordered_bitmap;
        unsigned long checked_bitmap;
        unsigned long flags;

        ASSERT(folio_test_private(folio) && folio_get_private(folio));
        ASSERT(sectors_per_page > 1);
        subpage = folio_get_private(folio);

        spin_lock_irqsave(&subpage->lock, flags);
        GET_SUBPAGE_BITMAP(subpage, fs_info, uptodate, &uptodate_bitmap);
        GET_SUBPAGE_BITMAP(subpage, fs_info, dirty, &dirty_bitmap);
        GET_SUBPAGE_BITMAP(subpage, fs_info, writeback, &writeback_bitmap);
        GET_SUBPAGE_BITMAP(subpage, fs_info, ordered, &ordered_bitmap);
        GET_SUBPAGE_BITMAP(subpage, fs_info, checked, &checked_bitmap);
        GET_SUBPAGE_BITMAP(subpage, fs_info, locked, &checked_bitmap);
        spin_unlock_irqrestore(&subpage->lock, flags);

        dump_page(folio_page(folio, 0), "btrfs subpage dump");
        btrfs_warn(fs_info,
"start=%llu len=%u page=%llu, bitmaps uptodate=%*pbl dirty=%*pbl writeback=%*pbl ordered=%*pbl checked=%*pbl",
                    start, len, folio_pos(folio),
                    sectors_per_page, &uptodate_bitmap,
                    sectors_per_page, &dirty_bitmap,
                    sectors_per_page, &writeback_bitmap,
                    sectors_per_page, &ordered_bitmap,
                    sectors_per_page, &checked_bitmap);
}

void btrfs_get_subpage_dirty_bitmap(struct btrfs_fs_info *fs_info,
                                    struct folio *folio,
                                    unsigned long *ret_bitmap)
{
        struct btrfs_subpage *subpage;
        unsigned long flags;

        ASSERT(folio_test_private(folio) && folio_get_private(folio));
        ASSERT(fs_info->sectors_per_page > 1);
        subpage = folio_get_private(folio);

        spin_lock_irqsave(&subpage->lock, flags);
        GET_SUBPAGE_BITMAP(subpage, fs_info, dirty, ret_bitmap);
        spin_unlock_irqrestore(&subpage->lock, flags);
}