Revision 9230a0b65b47fe6856c4468ec0175c4987e5bede authored by Dave Chinner on 20 November 2018, 06:50:08 UTC, committed by Darrick J. Wong on 21 November 2018, 18:10:53 UTC
Long saga. There have been days spent following this through dead end after dead end in multi-GB event traces. This morning, after writing a trace-cmd wrapper that enabled me to be more selective about XFS trace points, I discovered that I could get just enough essential tracepoints enabled that there was a 50:50 chance the fsx config would fail at ~115k ops. If it didn't fail at op 115547, I stopped fsx at op 115548 anyway. That gave me two traces - one where the problem manifested, and one where it didn't. After refining the traces to have the necessary information, I found that in the failing case there was a real extent in the COW fork compared to an unwritten extent in the working case. Walking back through the two traces to the point where the CWO fork extents actually diverged, I found that the bad case had an extra unwritten extent in it. This is likely because the bug it led me to had triggered multiple times in those 115k ops, leaving stray COW extents around. What I saw was a COW delalloc conversion to an unwritten extent (as they should always be through xfs_iomap_write_allocate()) resulted in a /written extent/: xfs_writepage: dev 259:0 ino 0x83 pgoff 0x17000 size 0x79a00 offset 0 length 0 xfs_iext_remove: dev 259:0 ino 0x83 state RC|LF|RF|COW cur 0xffff888247b899c0/2 offset 32 block 152 count 20 flag 1 caller xfs_bmap_add_extent_delay_real xfs_bmap_pre_update: dev 259:0 ino 0x83 state RC|LF|RF|COW cur 0xffff888247b899c0/1 offset 1 block 4503599627239429 count 31 flag 0 caller xfs_bmap_add_extent_delay_real xfs_bmap_post_update: dev 259:0 ino 0x83 state RC|LF|RF|COW cur 0xffff888247b899c0/1 offset 1 block 121 count 51 flag 0 caller xfs_bmap_add_ex Basically, Cow fork before: 0 1 32 52 +H+DDDDDDDDDDDD+UUUUUUUUUUU+ PREV RIGHT COW delalloc conversion allocates: 1 32 +uuuuuuuuuuuu+ NEW And the result according to the xfs_bmap_post_update trace was: 0 1 32 52 +H+wwwwwwwwwwwwwwwwwwwwwwww+ PREV Which is clearly wrong - it should be a merged unwritten extent, not an unwritten extent. That lead me to look at the LEFT_FILLING|RIGHT_FILLING|RIGHT_CONTIG case in xfs_bmap_add_extent_delay_real(), and sure enough, there's the bug. It takes the old delalloc extent (PREV) and adds the length of the RIGHT extent to it, takes the start block from NEW, removes the RIGHT extent and then updates PREV with the new extent. What it fails to do is update PREV.br_state. For delalloc, this is always XFS_EXT_NORM, while in this case we are converting the delayed allocation to unwritten, so it needs to be updated to XFS_EXT_UNWRITTEN. This LF|RF|RC case does not do this, and so the resultant extent is always written. And that's the bug I've been chasing for a week - a bmap btree bug, not a reflink/dedupe/copy_file_range bug, but a BMBT bug introduced with the recent in core extent tree scalability enhancements. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-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>
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nl80211.h
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __NET_WIRELESS_NL80211_H
#define __NET_WIRELESS_NL80211_H
#include "core.h"
int nl80211_init(void);
void nl80211_exit(void);
void nl80211_notify_wiphy(struct cfg80211_registered_device *rdev,
enum nl80211_commands cmd);
void nl80211_notify_iface(struct cfg80211_registered_device *rdev,
struct wireless_dev *wdev,
enum nl80211_commands cmd);
void nl80211_send_scan_start(struct cfg80211_registered_device *rdev,
struct wireless_dev *wdev);
struct sk_buff *nl80211_build_scan_msg(struct cfg80211_registered_device *rdev,
struct wireless_dev *wdev, bool aborted);
void nl80211_send_scan_msg(struct cfg80211_registered_device *rdev,
struct sk_buff *msg);
void nl80211_send_sched_scan(struct cfg80211_sched_scan_request *req, u32 cmd);
void nl80211_common_reg_change_event(enum nl80211_commands cmd_id,
struct regulatory_request *request);
static inline void
nl80211_send_reg_change_event(struct regulatory_request *request)
{
nl80211_common_reg_change_event(NL80211_CMD_REG_CHANGE, request);
}
static inline void
nl80211_send_wiphy_reg_change_event(struct regulatory_request *request)
{
nl80211_common_reg_change_event(NL80211_CMD_WIPHY_REG_CHANGE, request);
}
void nl80211_send_rx_auth(struct cfg80211_registered_device *rdev,
struct net_device *netdev,
const u8 *buf, size_t len, gfp_t gfp);
void nl80211_send_rx_assoc(struct cfg80211_registered_device *rdev,
struct net_device *netdev,
const u8 *buf, size_t len, gfp_t gfp,
int uapsd_queues);
void nl80211_send_deauth(struct cfg80211_registered_device *rdev,
struct net_device *netdev,
const u8 *buf, size_t len, gfp_t gfp);
void nl80211_send_disassoc(struct cfg80211_registered_device *rdev,
struct net_device *netdev,
const u8 *buf, size_t len, gfp_t gfp);
void nl80211_send_auth_timeout(struct cfg80211_registered_device *rdev,
struct net_device *netdev,
const u8 *addr, gfp_t gfp);
void nl80211_send_assoc_timeout(struct cfg80211_registered_device *rdev,
struct net_device *netdev,
const u8 *addr, gfp_t gfp);
void nl80211_send_connect_result(struct cfg80211_registered_device *rdev,
struct net_device *netdev,
struct cfg80211_connect_resp_params *params,
gfp_t gfp);
void nl80211_send_roamed(struct cfg80211_registered_device *rdev,
struct net_device *netdev,
struct cfg80211_roam_info *info, gfp_t gfp);
void nl80211_send_port_authorized(struct cfg80211_registered_device *rdev,
struct net_device *netdev, const u8 *bssid);
void nl80211_send_disconnected(struct cfg80211_registered_device *rdev,
struct net_device *netdev, u16 reason,
const u8 *ie, size_t ie_len, bool from_ap);
void
nl80211_michael_mic_failure(struct cfg80211_registered_device *rdev,
struct net_device *netdev, const u8 *addr,
enum nl80211_key_type key_type,
int key_id, const u8 *tsc, gfp_t gfp);
void
nl80211_send_beacon_hint_event(struct wiphy *wiphy,
struct ieee80211_channel *channel_before,
struct ieee80211_channel *channel_after);
void nl80211_send_ibss_bssid(struct cfg80211_registered_device *rdev,
struct net_device *netdev, const u8 *bssid,
gfp_t gfp);
int nl80211_send_mgmt(struct cfg80211_registered_device *rdev,
struct wireless_dev *wdev, u32 nlpid,
int freq, int sig_dbm,
const u8 *buf, size_t len, u32 flags, gfp_t gfp);
void
nl80211_radar_notify(struct cfg80211_registered_device *rdev,
const struct cfg80211_chan_def *chandef,
enum nl80211_radar_event event,
struct net_device *netdev, gfp_t gfp);
void nl80211_send_ap_stopped(struct wireless_dev *wdev);
void cfg80211_rdev_free_coalesce(struct cfg80211_registered_device *rdev);
#endif /* __NET_WIRELESS_NL80211_H */
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