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Make zc_nvlist_src_size limit tunable

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We limit the size of nvlists passed to the kernel so a user cannot make
the kernel do an unreasonably large allocation.  On FreeBSD this limit
was 128 kiB, which turns out to be a bit too small when doing some
operations involving a large number of datasets or snapshots, for
example replication.

Make this limit tunable, with a platform-specific auto default.
Linux keeps its limit at KMALLOC_MAX_SIZE. FreeBSD uses 1/4 of the
system limit on user wired memory, which allows it to scale depending
on system configuration.

Reviewed-by: Matt Macy <mmacy@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <freqlabs@FreeBSD.org>
Issue #6572 
Closes #10706
This commit is contained in:
Ryan Moeller
2020-08-18 12:33:55 -04:00
committed by GitHub
parent 663a070c92
commit 009cc8e884
6 changed files with 51 additions and 4 deletions
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module/zfs/zfs_ioctl.c
+10 -2
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@@ -225,8 +225,9 @@ zfsdev_state_t *zfsdev_state_list;
/*
* Limit maximum nvlist size. We don't want users passing in insane values
* for zc->zc_nvlist_src_size, since we will need to allocate that much memory.
* Defaults to 0=auto which is handled by platform code.
*/
#define MAX_NVLIST_SRC_SIZE KMALLOC_MAX_SIZE
unsigned long zfs_max_nvlist_src_size = 0;
uint_t zfs_fsyncer_key;
uint_t zfs_allow_log_key;
@@ -7341,6 +7342,7 @@ zfsdev_ioctl_common(uint_t vecnum, zfs_cmd_t *zc, int flag)
int error, cmd;
const zfs_ioc_vec_t *vec;
char *saved_poolname = NULL;
uint64_t max_nvlist_src_size;
size_t saved_poolname_len = 0;
nvlist_t *innvl = NULL;
fstrans_cookie_t cookie;
@@ -7360,7 +7362,8 @@ zfsdev_ioctl_common(uint_t vecnum, zfs_cmd_t *zc, int flag)
return (SET_ERROR(ZFS_ERR_IOC_CMD_UNAVAIL));
zc->zc_iflags = flag & FKIOCTL;
if (zc->zc_nvlist_src_size > MAX_NVLIST_SRC_SIZE) {
max_nvlist_src_size = zfs_max_nvlist_src_size_os();
if (zc->zc_nvlist_src_size > max_nvlist_src_size) {
/*
* Make sure the user doesn't pass in an insane value for
* zc_nvlist_src_size. We have to check, since we will end
@@ -7593,3 +7596,8 @@ zfs_kmod_fini(void)
tsd_destroy(&rrw_tsd_key);
tsd_destroy(&zfs_allow_log_key);
}
/* BEGIN CSTYLED */
ZFS_MODULE_PARAM(zfs, zfs_, max_nvlist_src_size, ULONG, ZMOD_RW,
"Maximum size in bytes allowed for src nvlist passed with ZFS ioctls");
/* END CSTYLED */