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btrfs: Avoid a rescan for a device which was already not found

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Currently read from missing device triggers rescan. However, it is never
recorded that the device is missing. So, each read of a missing device
triggers rescan again and again. This behavior causes a lot of unneeded
rescans leading to huge slowdowns.

This patch fixes above mentioned issue. Information about missing devices
is stored in the data->devices_attached[] array as NULL value in dev
member. Rescan is triggered only if no information is found for a given
device. This means that only first time read triggers rescan.

The patch drops premature return. This way data->devices_attached[] is
filled even when a given device is missing.

Signed-off-by: Goffredo Baroncelli <kreikack@inwind.it>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Goffredo Baroncelli 2018-10-22 19:29:34 +02:00 committed by Vincent Batts
parent 3f086df7ea
commit 41b8d7ba50
1 changed files with 9 additions and 8 deletions
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17
grub-core/fs/btrfs.c
View file

@ -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;
}
@ -897,7 +897,7 @@ 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",
@ -974,7 +974,8 @@ 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);