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Btrfs: make sure compressed bios don't complete too soon

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When writing a compressed extent, a number of bios are created that
point to a single struct compressed_bio.  At end_io time an atomic counter in
the compressed_bio struct makes sure that all of the bios have finished
before final end_io processing is done.

But when multiple bios are needed to write a compressed extent, the
counter was being incremented after the first bio was sent to submit_bio.
It is possible the bio will complete before the counter is incremented,
making the end_io handler free the compressed_bio struct before
processing is finished.

The fix is to increment the atomic counter before bio submission,
both for compressed reads and writes.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2008-11-07 12:35:44 -05:00
parent 4366211ccd
commit af09abfece
1 changed files with 15 additions and 2 deletions
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17
fs/btrfs/compression.c
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@ -314,6 +314,13 @@ int btrfs_submit_compressed_write(struct inode *inode, u64 start,
PAGE_CACHE_SIZE) {
bio_get(bio);
/*
* 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
*/
atomic_inc(&cb->pending_bios);
ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
BUG_ON(ret);
@ -323,7 +330,6 @@ int btrfs_submit_compressed_write(struct inode *inode, u64 start,
bio_put(bio);
bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
atomic_inc(&cb->pending_bios);
bio->bi_private = cb;
bio->bi_end_io = end_compressed_bio_write;
bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
@ -573,6 +579,14 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
BUG_ON(ret);
/*
* 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
*/
atomic_inc(&cb->pending_bios);
ret = btrfs_map_bio(root, READ, comp_bio, 0, 0);
BUG_ON(ret);
@ -580,7 +594,6 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
GFP_NOFS);
atomic_inc(&cb->pending_bios);
comp_bio->bi_private = cb;
comp_bio->bi_end_io = end_compressed_bio_read;