btrfs, block: move REQ_CGROUP_PUNT to btrfs

REQ_CGROUP_PUNT is a bit annoying as it is hard to follow and adds
a branch to the bio submission hot path.  To fix this, export
blkcg_punt_bio_submit and let btrfs call it directly.  Add a new
REQ_FS_PRIVATE flag for btrfs to indicate to it's own low-level
bio submission code that a punt to the cgroup submission helper
is required.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index bd50b55bdb61353188543719fa992f8d1a7192eb..9f5f3263c1781eceb1bc362815e062c4ba2a80e4 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1688,24 +1688,27 @@ out_unlock:
 }
 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
 
-bool __blkcg_punt_bio_submit(struct bio *bio)
+/*
+ * When a shared kthread issues a bio for a cgroup, doing so synchronously can
+ * lead to priority inversions as the kthread can be trapped waiting for that
+ * cgroup.  Use this helper instead of submit_bio to punt the actual issuing to
+ * a dedicated per-blkcg work item to avoid such priority inversions.
+ */
+void blkcg_punt_bio_submit(struct bio *bio)
 {
        struct blkcg_gq *blkg = bio->bi_blkg;
 
-       /* consume the flag first */
-       bio->bi_opf &= ~REQ_CGROUP_PUNT;
-
-       /* never bounce for the root cgroup */
-       if (!blkg->parent)
-               return false;
-
-       spin_lock_bh(&blkg->async_bio_lock);
-       bio_list_add(&blkg->async_bios, bio);
-       spin_unlock_bh(&blkg->async_bio_lock);
-
-       queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
-       return true;
+       if (blkg->parent) {
+               spin_lock_bh(&blkg->async_bio_lock);
+               bio_list_add(&blkg->async_bios, bio);
+               spin_unlock_bh(&blkg->async_bio_lock);
+               queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
+       } else {
+               /* never bounce for the root cgroup */
+               submit_bio(bio);
+       }
 }
+EXPORT_SYMBOL_GPL(blkcg_punt_bio_submit);
 
 /*
  * Scale the accumulated delay based on how long it has been since we updated

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 9c5078755e5e19cbda6db1616746c7244dd6c2b1..64758ab9f1f134a31b638a92bb984dfd061fd038 100644 (file)
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -375,16 +375,6 @@ static inline void blkg_put(struct blkcg_gq *blkg)
                if (((d_blkg) = blkg_lookup(css_to_blkcg(pos_css),      \
                                            (p_blkg)->q)))
 
-bool __blkcg_punt_bio_submit(struct bio *bio);
-
-static inline bool blkcg_punt_bio_submit(struct bio *bio)
-{
-       if (bio->bi_opf & REQ_CGROUP_PUNT)
-               return __blkcg_punt_bio_submit(bio);
-       else
-               return false;
-}
-
 static inline void blkcg_bio_issue_init(struct bio *bio)
 {
        bio_issue_init(&bio->bi_issue, bio_sectors(bio));
@@ -506,8 +496,6 @@ static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return
 static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
 static inline void blkg_get(struct blkcg_gq *blkg) { }
 static inline void blkg_put(struct blkcg_gq *blkg) { }
-
-static inline bool blkcg_punt_bio_submit(struct bio *bio) { return false; }
 static inline void blkcg_bio_issue_init(struct bio *bio) { }
 static inline void blk_cgroup_bio_start(struct bio *bio) { }
 static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; }

diff --git a/block/blk-core.c b/block/blk-core.c
index 42926e6cb83c8e328cfd1e904989430737cc9326..478978dcb2bd50283e730afc169c0d180a5ce18c 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -830,9 +830,6 @@ EXPORT_SYMBOL(submit_bio_noacct);
  */
 void submit_bio(struct bio *bio)
 {
-       if (blkcg_punt_bio_submit(bio))
-               return;
-
        if (bio_op(bio) == REQ_OP_READ) {
                task_io_account_read(bio->bi_iter.bi_size);
                count_vm_events(PGPGIN, bio_sectors(bio));

diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
index afd2f90fdbffa922b8bf54e27017171fe9856bcb..ed5aa8a176b938af42731a58851af501a0e98f4c 100644 (file)
--- a/fs/btrfs/bio.c
+++ b/fs/btrfs/bio.c
@@ -435,7 +435,11 @@ static void btrfs_submit_dev_bio(struct btrfs_device *dev, struct bio *bio)
                dev->devid, bio->bi_iter.bi_size);
 
        btrfsic_check_bio(bio);
-       submit_bio(bio);
+
+       if (bio->bi_opf & REQ_BTRFS_CGROUP_PUNT)
+               blkcg_punt_bio_submit(bio);
+       else
+               submit_bio(bio);
 }
 
 static void btrfs_submit_mirrored_bio(struct btrfs_io_context *bioc, int dev_nr)
@@ -551,10 +555,10 @@ static void run_one_async_done(struct btrfs_work *work)
 
        /*
         * All of the bios that pass through here are from async helpers.
-        * Use REQ_CGROUP_PUNT to issue them from the owning cgroup's context.
-        * This changes nothing when cgroups aren't in use.
+        * Use REQ_BTRFS_CGROUP_PUNT to issue them from the owning cgroup's
+        * context.  This changes nothing when cgroups aren't in use.
         */
-       bio->bi_opf |= REQ_CGROUP_PUNT;
+       bio->bi_opf |= REQ_BTRFS_CGROUP_PUNT;
        __btrfs_submit_bio(bio, async->bioc, &async->smap, async->mirror_num);
 }
 

diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h
index dbf125f6fa336d9caa5d38abdf3bd6d1eb28d4d2..8edf3c35eead906c5429a23be4de41ae44ab909d 100644 (file)
--- a/fs/btrfs/bio.h
+++ b/fs/btrfs/bio.h
@@ -88,6 +88,9 @@ static inline void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status)
 /* Bio only refers to one ordered extent. */
 #define REQ_BTRFS_ONE_ORDERED                  REQ_DRV
 
+/* Submit using blkcg_punt_bio_submit. */
+#define REQ_BTRFS_CGROUP_PUNT                  REQ_FS_PRIVATE
+
 void btrfs_submit_bio(struct btrfs_bio *bbio, int mirror_num);
 int btrfs_repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
                            u64 length, u64 logical, struct page *page,

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index f5702b1e2b86b0d23491503578796a375a1f0001..f40e4a002f789aeedbca6a66da5335fd806c5626 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2538,7 +2538,7 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end)
        struct btrfs_bio_ctrl bio_ctrl = {
                .wbc = &wbc_writepages,
                /* We're called from an async helper function */
-               .opf = REQ_OP_WRITE | REQ_CGROUP_PUNT |
+               .opf = REQ_OP_WRITE | REQ_BTRFS_CGROUP_PUNT |
                        wbc_to_write_flags(&wbc_writepages),
                .extent_locked = 1,
        };

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5c216cab2076cf62829cb32bd90edb3382c5af15..93e16a408f4310733ca001730056b880fa8079a1 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1616,7 +1616,7 @@ static int cow_file_range_async(struct btrfs_inode *inode,
                if (blkcg_css != blkcg_root_css) {
                        css_get(blkcg_css);
                        async_chunk[i].blkcg_css = blkcg_css;
-                       async_chunk[i].write_flags |= REQ_CGROUP_PUNT;
+                       async_chunk[i].write_flags |= REQ_BTRFS_CGROUP_PUNT;
                } else {
                        async_chunk[i].blkcg_css = NULL;
                }

diff --git a/include/linux/bio.h b/include/linux/bio.h
index d766be7152e15186d325f991cc49d66ff816a5dc..b3e7529ff55eb3966c474ee8bc1e50bfea0ded69 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -500,6 +500,7 @@ void bio_associate_blkg(struct bio *bio);
 void bio_associate_blkg_from_css(struct bio *bio,
                                 struct cgroup_subsys_state *css);
 void bio_clone_blkg_association(struct bio *dst, struct bio *src);
+void blkcg_punt_bio_submit(struct bio *bio);
 #else  /* CONFIG_BLK_CGROUP */
 static inline void bio_associate_blkg(struct bio *bio) { }
 static inline void bio_associate_blkg_from_css(struct bio *bio,
@@ -507,6 +508,10 @@ static inline void bio_associate_blkg_from_css(struct bio *bio,
 { }
 static inline void bio_clone_blkg_association(struct bio *dst,
                                              struct bio *src) { }
+static inline void blkcg_punt_bio_submit(struct bio *bio)
+{
+       submit_bio(bio);
+}
 #endif /* CONFIG_BLK_CGROUP */
 
 static inline void bio_set_dev(struct bio *bio, struct block_device *bdev)

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 99be590f952f6e69d47900b970f05f0195e98798..fb8843990d288e7b507a22055af4eee259bfbf99 100644 (file)
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -404,18 +404,11 @@ enum req_flag_bits {
        __REQ_RAHEAD,           /* read ahead, can fail anytime */
        __REQ_BACKGROUND,       /* background IO */
        __REQ_NOWAIT,           /* Don't wait if request will block */
-       /*
-        * When a shared kthread needs to issue a bio for a cgroup, doing
-        * so synchronously can lead to priority inversions as the kthread
-        * can be trapped waiting for that cgroup.  CGROUP_PUNT flag makes
-        * submit_bio() punt the actual issuing to a dedicated per-blkcg
-        * work item to avoid such priority inversions.
-        */
-       __REQ_CGROUP_PUNT,
        __REQ_POLLED,           /* caller polls for completion using bio_poll */
        __REQ_ALLOC_CACHE,      /* allocate IO from cache if available */
        __REQ_SWAP,             /* swap I/O */
        __REQ_DRV,              /* for driver use */
+       __REQ_FS_PRIVATE,       /* for file system (submitter) use */
 
        /*
         * Command specific flags, keep last:
@@ -443,14 +436,13 @@ enum req_flag_bits {
 #define REQ_RAHEAD     (__force blk_opf_t)(1ULL << __REQ_RAHEAD)
 #define REQ_BACKGROUND (__force blk_opf_t)(1ULL << __REQ_BACKGROUND)
 #define REQ_NOWAIT     (__force blk_opf_t)(1ULL << __REQ_NOWAIT)
-#define REQ_CGROUP_PUNT        (__force blk_opf_t)(1ULL << __REQ_CGROUP_PUNT)
-
-#define REQ_NOUNMAP    (__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
 #define REQ_POLLED     (__force blk_opf_t)(1ULL << __REQ_POLLED)
 #define REQ_ALLOC_CACHE        (__force blk_opf_t)(1ULL << __REQ_ALLOC_CACHE)
-
-#define REQ_DRV                (__force blk_opf_t)(1ULL << __REQ_DRV)
 #define REQ_SWAP       (__force blk_opf_t)(1ULL << __REQ_SWAP)
+#define REQ_DRV                (__force blk_opf_t)(1ULL << __REQ_DRV)
+#define REQ_FS_PRIVATE (__force blk_opf_t)(1ULL << __REQ_FS_PRIVATE)
+
+#define REQ_NOUNMAP    (__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
 
 #define REQ_FAILFAST_MASK \
        (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)