btrfs: raid56: remove sector_ptr::has_paddr member

We can use paddr -1 as an indicator for unset/uninitialized paddr.

We can not use 0 paddr, unlike virtual address 0 which is never mapped
thus will always trigger a page fault, physical address 0 may be a valid
page.

So here we follow swiotlb to use (paddr)-1 as a special indicator for
invalid/unset physical address.

Even if the PFN may still be valid, our usage of the physical address
should always be aligned to fs block size (or page size for bs > ps
cases), thus such -1 paddr should never be a valid one.

With this special -1 paddr, we can get rid of has_paddr member and save
1 byte for sector_ptr structure.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 302f20d8c33518dc6367fe82bb719000de1cdd99..c057491c842b7dcc3d0bfbbb1184f602f4014e7c 100644 (file)
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -133,6 +133,12 @@ struct btrfs_stripe_hash_table {
        struct btrfs_stripe_hash table[];
 };
 
+/*
+ * The PFN may still be valid, but our paddrs should always be block size
+ * aligned, thus such -1 paddr is definitely not a valid one.
+ */
+#define INVALID_PADDR  (~(phys_addr_t)0)
+
 /*
  * A structure to present a sector inside a page, the length is fixed to
  * sectorsize;
@@ -141,9 +147,10 @@ struct sector_ptr {
        /*
         * Blocks from the bio list can still be highmem.
         * So here we use physical address to present a page and the offset inside it.
+        *
+        * If it's INVALID_PADDR then it's not set.
         */
        phys_addr_t paddr;
-       bool has_paddr;
        bool uptodate;
 };
 
@@ -263,7 +270,7 @@ static void cache_rbio_pages(struct btrfs_raid_bio *rbio)
 
        for (i = 0; i < rbio->nr_sectors; i++) {
                /* Some range not covered by bio (partial write), skip it */
-               if (!rbio->bio_sectors[i].has_paddr) {
+               if (rbio->bio_sectors[i].paddr == INVALID_PADDR) {
                        /*
                         * Even if the sector is not covered by bio, if it is
                         * a data sector it should still be uptodate as it is
@@ -335,7 +342,6 @@ static void index_stripe_sectors(struct btrfs_raid_bio *rbio)
                if (!rbio->stripe_pages[page_index])
                        continue;
 
-               rbio->stripe_sectors[i].has_paddr = true;
                rbio->stripe_sectors[i].paddr =
                        page_to_phys(rbio->stripe_pages[page_index]) +
                        offset_in_page(offset);
@@ -972,9 +978,9 @@ static struct sector_ptr *sector_in_rbio(struct btrfs_raid_bio *rbio,
 
        spin_lock(&rbio->bio_list_lock);
        sector = &rbio->bio_sectors[index];
-       if (sector->has_paddr || bio_list_only) {
+       if (sector->paddr != INVALID_PADDR || bio_list_only) {
                /* Don't return sector without a valid page pointer */
-               if (!sector->has_paddr)
+               if (sector->paddr == INVALID_PADDR)
                        sector = NULL;
                spin_unlock(&rbio->bio_list_lock);
                return sector;
@@ -1032,6 +1038,10 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_fs_info *fs_info,
                kfree(rbio);
                return ERR_PTR(-ENOMEM);
        }
+       for (int i = 0; i < num_sectors; i++) {
+               rbio->stripe_sectors[i].paddr = INVALID_PADDR;
+               rbio->bio_sectors[i].paddr = INVALID_PADDR;
+       }
 
        bio_list_init(&rbio->bio_list);
        init_waitqueue_head(&rbio->io_wait);
@@ -1152,7 +1162,7 @@ static int rbio_add_io_sector(struct btrfs_raid_bio *rbio,
                           rbio, stripe_nr);
        ASSERT_RBIO_SECTOR(sector_nr >= 0 && sector_nr < rbio->stripe_nsectors,
                           rbio, sector_nr);
-       ASSERT(sector->has_paddr);
+       ASSERT(sector->paddr != INVALID_PADDR);
 
        stripe = &rbio->bioc->stripes[stripe_nr];
        disk_start = stripe->physical + sector_nr * sectorsize;
@@ -1216,7 +1226,6 @@ static void index_one_bio(struct btrfs_raid_bio *rbio, struct bio *bio)
                unsigned int index = (offset >> sectorsize_bits);
                struct sector_ptr *sector = &rbio->bio_sectors[index];
 
-               sector->has_paddr = true;
                sector->paddr = paddr;
                offset += sectorsize;
        }
@@ -1299,7 +1308,7 @@ static void assert_rbio(struct btrfs_raid_bio *rbio)
 static inline void *kmap_local_sector(const struct sector_ptr *sector)
 {
        /* The sector pointer must have a page mapped to it. */
-       ASSERT(sector->has_paddr);
+       ASSERT(sector->paddr != INVALID_PADDR);
 
        return kmap_local_page(phys_to_page(sector->paddr)) +
               offset_in_page(sector->paddr);
@@ -1498,7 +1507,7 @@ static struct sector_ptr *find_stripe_sector(struct btrfs_raid_bio *rbio,
        for (i = 0; i < rbio->nr_sectors; i++) {
                struct sector_ptr *sector = &rbio->stripe_sectors[i];
 
-               if (sector->has_paddr && sector->paddr == paddr)
+               if (sector->paddr == paddr)
                        return sector;
        }
        return NULL;
@@ -1532,8 +1541,7 @@ static int get_bio_sector_nr(struct btrfs_raid_bio *rbio, struct bio *bio)
        for (i = 0; i < rbio->nr_sectors; i++) {
                if (rbio->stripe_sectors[i].paddr == bvec_paddr)
                        break;
-               if (rbio->bio_sectors[i].has_paddr &&
-                   rbio->bio_sectors[i].paddr == bvec_paddr)
+               if (rbio->bio_sectors[i].paddr == bvec_paddr)
                        break;
        }
        ASSERT(i < rbio->nr_sectors);
@@ -2317,7 +2325,7 @@ static bool need_read_stripe_sectors(struct btrfs_raid_bio *rbio)
                 * thus this rbio can not be cached one, as cached one must
                 * have all its data sectors present and uptodate.
                 */
-               if (!sector->has_paddr || !sector->uptodate)
+               if (sector->paddr == INVALID_PADDR || !sector->uptodate)
                        return true;
        }
        return false;
@@ -2508,8 +2516,8 @@ static int finish_parity_scrub(struct btrfs_raid_bio *rbio)
        int sectornr;
        bool has_qstripe;
        struct page *page;
-       struct sector_ptr p_sector = { 0 };
-       struct sector_ptr q_sector = { 0 };
+       struct sector_ptr p_sector = { .paddr = INVALID_PADDR };
+       struct sector_ptr q_sector = { .paddr = INVALID_PADDR };
        struct bio_list bio_list;
        int is_replace = 0;
        int ret;
@@ -2542,7 +2550,6 @@ static int finish_parity_scrub(struct btrfs_raid_bio *rbio)
        page = alloc_page(GFP_NOFS);
        if (!page)
                return -ENOMEM;
-       p_sector.has_paddr = true;
        p_sector.paddr = page_to_phys(page);
        p_sector.uptodate = 1;
        page = NULL;
@@ -2552,10 +2559,9 @@ static int finish_parity_scrub(struct btrfs_raid_bio *rbio)
                page = alloc_page(GFP_NOFS);
                if (!page) {
                        __free_page(phys_to_page(p_sector.paddr));
-                       p_sector.has_paddr = false;
+                       p_sector.paddr = INVALID_PADDR;
                        return -ENOMEM;
                }
-               q_sector.has_paddr = true;
                q_sector.paddr = page_to_phys(page);
                q_sector.uptodate = 1;
                page = NULL;
@@ -2604,10 +2610,10 @@ static int finish_parity_scrub(struct btrfs_raid_bio *rbio)
 
        kunmap_local(pointers[nr_data]);
        __free_page(phys_to_page(p_sector.paddr));
-       p_sector.has_paddr = false;
-       if (q_sector.has_paddr) {
+       p_sector.paddr = INVALID_PADDR;
+       if (q_sector.paddr != INVALID_PADDR) {
                __free_page(phys_to_page(q_sector.paddr));
-               q_sector.has_paddr = false;
+               q_sector.paddr = INVALID_PADDR;
        }
 
        /*