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Use fallocate() with an offset starting at the missing data

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This works better with Btrfs.
This commit is contained in:
Andrea Mazzoleni 2017-11-24 21:56:12 +01:00
parent 701b0e67e1
commit 68563650c9
2 changed files with 12 additions and 3 deletions
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1
HISTORY
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@ -13,6 +13,7 @@ SnapRAID HISTORY
* In Linux use by default the advise "discard" mode instead of "flush".
This avoids to swap-out the other process memory, leaving the system
more responsive.
* Changed the fallocate() use to work better with Btrfs with parity disks.
* Changed the --test-io-stats screen to print the file name in process
for each disk.

14
cmdline/parity.c
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@ -256,10 +256,12 @@ bail:
/* LCOV_EXCL_STOP */
}
static int parity_handle_grow(struct snapraid_split_handle* split, data_off_t size, int skip_fallocate)
static int parity_handle_grow(struct snapraid_split_handle* split, data_off_t previous_size, data_off_t size, int skip_fallocate)
{
int ret;
(void)previous_size;
/* simulate a failure for testing limits */
if (split->limit_size != 0 && size > (data_off_t)split->limit_size)
return -1;
@ -276,8 +278,14 @@ static int parity_handle_grow(struct snapraid_split_handle* split, data_off_t si
*
* See: fallocate vs posix_fallocate
* http://stackoverflow.com/questions/14063046/fallocate-vs-posix-fallocate
*
* To work better with Btrfs, use as offset the previous allocated size.
* Otherwise Btrfs will count as space needed even the already allocated one.
*
* See: Massive loss of disk space
* https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg66454.html
*/
ret = fallocate(split->f, 0, 0, size);
ret = fallocate(split->f, 0, previous_size, size - previous_size);
/*
* In some legacy system fallocate() may return the error number
@ -422,7 +430,7 @@ static int parity_handle_fill(struct snapraid_split_handle* split, data_off_t si
/* mask out the bit we process */
delta &= ~run;
ret = parity_handle_grow(split, base + run, skip_fallocate);
ret = parity_handle_grow(split, base, base + run, skip_fallocate);
if (ret != 0) {
/* we cannot grow, fallback enabling all the smaller bits */
delta = run - 1;