@@ -193,6 +193,34 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
return 0;
}
+/*
+ * Reduce bio and io accounting for a compressed_bio with its coresponding bio.
+ *
+ * Return true if there is no pending bio nor io.
+ * Return false otherwise.
+ */
+static bool dec_and_test_compressed_bio(struct compressed_bio *cb,
+ struct bio *bio)
+{
+ struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
+ unsigned int bi_size = bio->bi_iter.bi_size;
+ bool last_bio = false;
+ bool last_io = false;
+
+ if (bio->bi_status)
+ cb->errors = 1;
+
+ last_bio = atomic_dec_and_test(&cb->pending_bios);
+ last_io = atomic_sub_and_test(bi_size >> fs_info->sectorsize_bits,
+ &cb->io_sectors);
+
+ /*
+ * We can only finish the compressed bio if no pending bio and all io
+ * submitted.
+ */
+ return last_bio && last_io;
+}
+
/* when we finish reading compressed pages from the disk, we
* decompress them and then run the bio end_io routines on the
* decompressed pages (in the inode address space).
@@ -212,13 +240,7 @@ static void end_compressed_bio_read(struct bio *bio)
unsigned int mirror = btrfs_io_bio(bio)->mirror_num;
int ret = 0;
- if (bio->bi_status)
- cb->errors = 1;
-
- /* if there are more bios still pending for this compressed
- * extent, just exit
- */
- if (!refcount_dec_and_test(&cb->pending_bios))
+ if (!dec_and_test_compressed_bio(cb, bio))
goto out;
/*
@@ -336,13 +358,7 @@ static void end_compressed_bio_write(struct bio *bio)
struct page *page;
unsigned int index;
- if (bio->bi_status)
- cb->errors = 1;
-
- /* if there are more bios still pending for this compressed
- * extent, just exit
- */
- if (!refcount_dec_and_test(&cb->pending_bios))
+ if (!dec_and_test_compressed_bio(cb, bio))
goto out;
/* ok, we're the last bio for this extent, step one is to
@@ -408,7 +424,8 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
if (!cb)
return BLK_STS_RESOURCE;
- refcount_set(&cb->pending_bios, 0);
+ atomic_set(&cb->pending_bios, 0);
+ atomic_set(&cb->io_sectors, compressed_len >> fs_info->sectorsize_bits);
cb->errors = 0;
cb->inode = &inode->vfs_inode;
cb->start = start;
@@ -441,7 +458,6 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
bio->bi_opf |= REQ_CGROUP_PUNT;
kthread_associate_blkcg(blkcg_css);
}
- refcount_set(&cb->pending_bios, 1);
/* create and submit bios for the compressed pages */
bytes_left = compressed_len;
@@ -469,13 +485,7 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
page->mapping = NULL;
if (submit || len < PAGE_SIZE) {
- /*
- * inc the count before we submit the bio so
- * we know the end IO handler won't happen before
- * we inc the count. Otherwise, the cb might get
- * freed before we're done setting it up
- */
- refcount_inc(&cb->pending_bios);
+ atomic_inc(&cb->pending_bios);
ret = btrfs_bio_wq_end_io(fs_info, bio,
BTRFS_WQ_ENDIO_DATA);
BUG_ON(ret); /* -ENOMEM */
@@ -513,6 +523,7 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
cond_resched();
}
+ atomic_inc(&cb->pending_bios);
ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
BUG_ON(ret); /* -ENOMEM */
@@ -696,7 +707,8 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
if (!cb)
goto out;
- refcount_set(&cb->pending_bios, 0);
+ atomic_set(&cb->pending_bios, 0);
+ atomic_set(&cb->io_sectors, compressed_len >> fs_info->sectorsize_bits);
cb->errors = 0;
cb->inode = inode;
cb->mirror_num = mirror_num;
@@ -741,7 +753,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
comp_bio->bi_opf = REQ_OP_READ;
comp_bio->bi_private = cb;
comp_bio->bi_end_io = end_compressed_bio_read;
- refcount_set(&cb->pending_bios, 1);
for (pg_index = 0; pg_index < nr_pages; pg_index++) {
u32 pg_len = PAGE_SIZE;
@@ -770,18 +781,11 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
if (submit || bio_add_page(comp_bio, page, pg_len, 0) < pg_len) {
unsigned int nr_sectors;
+ atomic_inc(&cb->pending_bios);
ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
BTRFS_WQ_ENDIO_DATA);
BUG_ON(ret); /* -ENOMEM */
- /*
- * inc the count before we submit the bio so
- * we know the end IO handler won't happen before
- * we inc the count. Otherwise, the cb might get
- * freed before we're done setting it up
- */
- refcount_inc(&cb->pending_bios);
-
ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
BUG_ON(ret); /* -ENOMEM */
@@ -805,6 +809,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
cur_disk_byte += pg_len;
}
+ atomic_inc(&cb->pending_bios);
ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
BUG_ON(ret); /* -ENOMEM */
@@ -29,7 +29,15 @@ struct btrfs_inode;
struct compressed_bio {
/* number of bios pending for this compressed extent */
- refcount_t pending_bios;
+ atomic_t pending_bios;
+
+ /*
+ * Number of sectors which hasn't finished.
+ *
+ * Combined with pending_bios, we can manually finish the compressed_bio
+ * if we hit some error while there is still some pages not added.
+ */
+ atomic_t io_sectors;
/* Number of compressed pages in the array */
unsigned int nr_pages;
For btrfs_submit_compressed_read() and btrfs_submit_compressed_write(), we have a pretty weird dance around compressed_bio::pending_bios: btrfs_submit_compressed_read/write() { cb = kmalloc() refcount_set(&cb->pending_bios, 0); bio = btrfs_alloc_bio(); /* NOTE here, we haven't yet submitted any bio */ refcount_set(&cb->pending_bios, 1); for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) { if (submit) { /* Here we submit bio, but we always have one * extra pending_bios */ refcount_inc(&cb->pending_bios); ret = btrfs_map_bio(); } } /* Submit the last bio */ ret = btrfs_map_bio(); } There are two reasons why we do this: - compressed_bio::pending_bios is a refcount Thus if it's reduced to 0, it can not be increased again. - To ensure the compressed_bio is not freed by some submitted bios If the submitted bio is finished before the next bio submitted, we can free the compressed_bio completely. But the above code is sometimes confusing, and we can do it better by just introduce a new member, compressed_bio::io_sectors. With that member, we can easily distinguish if we're really the last bio at endio time, and even allows us to remove some BUG_ON() later, as we now know how many bytes are not yet submitted. With this new member, now compressed_bio::pending_bios really indicates the pending bios, without any special handling needed. Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/compression.c | 71 ++++++++++++++++++++++-------------------- fs/btrfs/compression.h | 10 +++++- 2 files changed, 47 insertions(+), 34 deletions(-)