From: Goffredo Baroncelli <[email protected]> Change the behavior of find_device(): before the patch, a read of a missed device may trigger a rescan. However, it is never recorded that a device is missed, so each single read of a missed device may triggers a rescan. It is the caller who decides if a rescan is performed in case of a missed device. And it does quite often, without considering if in the past a devices was already found as "missed" This behavior causes a lot of unneeded rescan, causing a huge slowdown in case of a missed device.
After the patch, the "missed device" information is stored in the data->devices_attached[] array (as a NULL value in the field dev). A rescan is triggered only if no information at all is found. This means that only the first time a read of a missed device triggers a rescan. The change in the code is done removing "return NULL" when the disk is not found. So it is always executed the code which stores in the data->devices_attached[] array the value returned by grub_device_iterate(): NULL if the device is missed, or a valid data otherwise. Signed-off-by: Goffredo Baroncelli <[email protected]> --- grub-core/fs/btrfs.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c index 2b1dd7dd4..c07d91657 100644 --- a/grub-core/fs/btrfs.c +++ b/grub-core/fs/btrfs.c @@ -588,7 +588,7 @@ find_device_iter (const char *name, void *data) } static grub_device_t -find_device (struct grub_btrfs_data *data, grub_uint64_t id, int do_rescan) +find_device (struct grub_btrfs_data *data, grub_uint64_t id) { struct find_device_ctx ctx = { .data = data, @@ -600,10 +600,9 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id, int do_rescan) for (i = 0; i < data->n_devices_attached; i++) if (id == data->devices_attached[i].id) return data->devices_attached[i].dev; - if (do_rescan) - grub_device_iterate (find_device_iter, &ctx); - if (!ctx.dev_found) - return NULL; + + grub_device_iterate (find_device_iter, &ctx); + data->n_devices_attached++; if (data->n_devices_attached > data->n_devices_allocated) { @@ -615,7 +614,8 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id, int do_rescan) * sizeof (data->devices_attached[0])); if (!data->devices_attached) { - grub_device_close (ctx.dev_found); + if (ctx.dev_found) + grub_device_close (ctx.dev_found); data->devices_attached = tmp; return NULL; } @@ -898,7 +898,7 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr, " for laddr 0x%" PRIxGRUB_UINT64_T "\n", paddr, addr); - dev = find_device (data, stripe->device_id, j); + dev = find_device (data, stripe->device_id); if (!dev) { grub_dprintf ("btrfs", @@ -975,7 +975,8 @@ grub_btrfs_unmount (struct grub_btrfs_data *data) unsigned i; /* The device 0 is closed one layer upper. */ for (i = 1; i < data->n_devices_attached; i++) - grub_device_close (data->devices_attached[i].dev); + if (data->devices_attached[i].dev) + grub_device_close (data->devices_attached[i].dev); grub_free (data->devices_attached); grub_free (data->extent); grub_free (data); -- 2.19.0
