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66ae56a53f
Add a mode where XFS never overwrites existing blocks in place. This
is to aid debugging our COW code, and also put infatructure in place
for things like possible future support for zoned block devices, which
can't support overwrites.
This mode is enabled globally by doing a:
echo 1 > /sys/fs/xfs/debug/always_cow
Note that the parameter is global to allow running all tests in xfstests
easily in this mode, which would not easily be possible with a per-fs
sysfs file.
In always_cow mode persistent preallocations are disabled, and fallocate
will fail when called with a 0 mode (with our without
FALLOC_FL_KEEP_SIZE), and not create unwritten extent for zeroed space
when called with FALLOC_FL_ZERO_RANGE or FALLOC_FL_UNSHARE_RANGE.
There are a few interesting xfstests failures when run in always_cow
mode:
- generic/392 fails because the bytes used in the file used to test
hole punch recovery are less after the log replay. This is
because the blocks written and then punched out are only freed
with a delay due to the logging mechanism.
- xfs/170 will fail as the already fragile file streams mechanism
doesn't seem to interact well with the COW allocator
- xfs/180 xfs/182 xfs/192 xfs/198 xfs/204 and xfs/208 will claim
the file system is badly fragmented, but there is not much we
can do to avoid that when always writing out of place
- xfs/205 fails because overwriting a file in always_cow mode
will require new space allocation and the assumption in the
test thus don't work anymore.
- xfs/326 fails to modify the file at all in always_cow mode after
injecting the refcount error, leading to an unexpected md5sum
after the remount, but that again is expected
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
101 lines
3.2 KiB
C
101 lines
3.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2001-2005 Silicon Graphics, Inc.
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* All Rights Reserved.
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*/
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#ifndef __XFS_SYSCTL_H__
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#define __XFS_SYSCTL_H__
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#include <linux/sysctl.h>
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/*
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* Tunable xfs parameters
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*/
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typedef struct xfs_sysctl_val {
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int min;
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int val;
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int max;
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} xfs_sysctl_val_t;
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typedef struct xfs_param {
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xfs_sysctl_val_t sgid_inherit; /* Inherit S_ISGID if process' GID is
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* not a member of parent dir GID. */
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xfs_sysctl_val_t symlink_mode; /* Link creat mode affected by umask */
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xfs_sysctl_val_t panic_mask; /* bitmask to cause panic on errors. */
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xfs_sysctl_val_t error_level; /* Degree of reporting for problems */
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xfs_sysctl_val_t syncd_timer; /* Interval between xfssyncd wakeups */
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xfs_sysctl_val_t stats_clear; /* Reset all XFS statistics to zero. */
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xfs_sysctl_val_t inherit_sync; /* Inherit the "sync" inode flag. */
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xfs_sysctl_val_t inherit_nodump;/* Inherit the "nodump" inode flag. */
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xfs_sysctl_val_t inherit_noatim;/* Inherit the "noatime" inode flag. */
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xfs_sysctl_val_t xfs_buf_timer; /* Interval between xfsbufd wakeups. */
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xfs_sysctl_val_t xfs_buf_age; /* Metadata buffer age before flush. */
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xfs_sysctl_val_t inherit_nosym; /* Inherit the "nosymlinks" flag. */
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xfs_sysctl_val_t rotorstep; /* inode32 AG rotoring control knob */
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xfs_sysctl_val_t inherit_nodfrg;/* Inherit the "nodefrag" inode flag. */
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xfs_sysctl_val_t fstrm_timer; /* Filestream dir-AG assoc'n timeout. */
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xfs_sysctl_val_t eofb_timer; /* Interval between eofb scan wakeups */
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xfs_sysctl_val_t cowb_timer; /* Interval between cowb scan wakeups */
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} xfs_param_t;
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/*
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* xfs_error_level:
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*
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* How much error reporting will be done when internal problems are
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* encountered. These problems normally return an EFSCORRUPTED to their
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* caller, with no other information reported.
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*
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* 0 No error reports
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* 1 Report EFSCORRUPTED errors that will cause a filesystem shutdown
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* 5 Report all EFSCORRUPTED errors (all of the above errors, plus any
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* additional errors that are known to not cause shutdowns)
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*
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* xfs_panic_mask bit 0x8 turns the error reports into panics
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*/
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enum {
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/* XFS_REFCACHE_SIZE = 1 */
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/* XFS_REFCACHE_PURGE = 2 */
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/* XFS_RESTRICT_CHOWN = 3 */
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XFS_SGID_INHERIT = 4,
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XFS_SYMLINK_MODE = 5,
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XFS_PANIC_MASK = 6,
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XFS_ERRLEVEL = 7,
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XFS_SYNCD_TIMER = 8,
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/* XFS_PROBE_DMAPI = 9 */
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/* XFS_PROBE_IOOPS = 10 */
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/* XFS_PROBE_QUOTA = 11 */
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XFS_STATS_CLEAR = 12,
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XFS_INHERIT_SYNC = 13,
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XFS_INHERIT_NODUMP = 14,
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XFS_INHERIT_NOATIME = 15,
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XFS_BUF_TIMER = 16,
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XFS_BUF_AGE = 17,
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/* XFS_IO_BYPASS = 18 */
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XFS_INHERIT_NOSYM = 19,
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XFS_ROTORSTEP = 20,
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XFS_INHERIT_NODFRG = 21,
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XFS_FILESTREAM_TIMER = 22,
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};
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extern xfs_param_t xfs_params;
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struct xfs_globals {
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int log_recovery_delay; /* log recovery delay (secs) */
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int mount_delay; /* mount setup delay (secs) */
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bool bug_on_assert; /* BUG() the kernel on assert failure */
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bool always_cow; /* use COW fork for all overwrites */
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};
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extern struct xfs_globals xfs_globals;
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#ifdef CONFIG_SYSCTL
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extern int xfs_sysctl_register(void);
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extern void xfs_sysctl_unregister(void);
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#else
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# define xfs_sysctl_register() (0)
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# define xfs_sysctl_unregister() do { } while (0)
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#endif /* CONFIG_SYSCTL */
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#endif /* __XFS_SYSCTL_H__ */
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