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btrfs: preallocate compression workspaces 

Preallocate one workspace for each compression type so we can guarantee
forward progress in the worst case. A failure cannot be a hard error as
we might not use compression at all on the filesystem. If we can't
allocate the workspaces later when need them, it might actually
deadlock, but in such situation the system has effectively not enough
memory to operate properly.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2016-04-27 02:55:15 +02:00
parent 6ac10a6ac2
commit f77dd0d6b2
1 changed files with 16 additions and 0 deletions
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16
fs/btrfs/compression.c
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@ -761,10 +761,26 @@ void __init btrfs_init_compress(void)
int i; int i;
for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) { for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
struct list_head *workspace;
INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws); INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws);
spin_lock_init(&btrfs_comp_ws[i].ws_lock); spin_lock_init(&btrfs_comp_ws[i].ws_lock);
atomic_set(&btrfs_comp_ws[i].total_ws, 0); atomic_set(&btrfs_comp_ws[i].total_ws, 0);
init_waitqueue_head(&btrfs_comp_ws[i].ws_wait); init_waitqueue_head(&btrfs_comp_ws[i].ws_wait);
/*
* Preallocate one workspace for each compression type so
* we can guarantee forward progress in the worst case
*/
workspace = btrfs_compress_op[i]->alloc_workspace();
if (IS_ERR(workspace)) {
printk(KERN_WARNING
"BTRFS: cannot preallocate compression workspace, will try later");
} else {
atomic_set(&btrfs_comp_ws[i].total_ws, 1);
btrfs_comp_ws[i].free_ws = 1;
list_add(workspace, &btrfs_comp_ws[i].idle_ws);
}
} }
} }