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Date: Wed, 15 May 2013 11:49:13 -0500
From: Alex Elder <elder@...tank.com>
To: Jim Schutt <jaschut@...dia.gov>
CC: ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] ceph: ceph_pagelist_append might sleep while atomic
On 05/15/2013 11:38 AM, Jim Schutt wrote:
> Ceph's encode_caps_cb() worked hard to not call __page_cache_alloc() while
> holding a lock, but it's spoiled because ceph_pagelist_addpage() always
> calls kmap(), which might sleep. Here's the result:
This looks good to me, but I admit I didn't take as close
a look at it this time.
I appreciate your updating the series to include the things
I mentioned.
I'll commit these for you, and I'll get confirmation on the
byte order thing as well.
Reviewed-by: Alex Elder <elder@...tank.com>
> [13439.295457] ceph: mds0 reconnect start
> [13439.300572] BUG: sleeping function called from invalid context at include/linux/highmem.h:58
> [13439.309243] in_atomic(): 1, irqs_disabled(): 0, pid: 12059, name: kworker/1:1
> [13439.316464] 5 locks held by kworker/1:1/12059:
> [13439.320998] #0: (ceph-msgr){......}, at: [<ffffffff810609f8>] process_one_work+0x218/0x480
> [13439.329701] #1: ((&(&con->work)->work)){......}, at: [<ffffffff810609f8>] process_one_work+0x218/0x480
> [13439.339446] #2: (&s->s_mutex){......}, at: [<ffffffffa046273c>] send_mds_reconnect+0xec/0x450 [ceph]
> [13439.349081] #3: (&mdsc->snap_rwsem){......}, at: [<ffffffffa04627be>] send_mds_reconnect+0x16e/0x450 [ceph]
> [13439.359278] #4: (file_lock_lock){......}, at: [<ffffffff811cadf5>] lock_flocks+0x15/0x20
> [13439.367816] Pid: 12059, comm: kworker/1:1 Tainted: G W 3.9.0-00358-g308ae61 #557
> [13439.376225] Call Trace:
> [13439.378757] [<ffffffff81076f4c>] __might_sleep+0xfc/0x110
> [13439.384353] [<ffffffffa03f4ce0>] ceph_pagelist_append+0x120/0x1b0 [libceph]
> [13439.391491] [<ffffffffa0448fe9>] ceph_encode_locks+0x89/0x190 [ceph]
> [13439.398035] [<ffffffff814ee849>] ? _raw_spin_lock+0x49/0x50
> [13439.403775] [<ffffffff811cadf5>] ? lock_flocks+0x15/0x20
> [13439.409277] [<ffffffffa045e2af>] encode_caps_cb+0x41f/0x4a0 [ceph]
> [13439.415622] [<ffffffff81196748>] ? igrab+0x28/0x70
> [13439.420610] [<ffffffffa045e9f8>] ? iterate_session_caps+0xe8/0x250 [ceph]
> [13439.427584] [<ffffffffa045ea25>] iterate_session_caps+0x115/0x250 [ceph]
> [13439.434499] [<ffffffffa045de90>] ? set_request_path_attr+0x2d0/0x2d0 [ceph]
> [13439.441646] [<ffffffffa0462888>] send_mds_reconnect+0x238/0x450 [ceph]
> [13439.448363] [<ffffffffa0464542>] ? ceph_mdsmap_decode+0x5e2/0x770 [ceph]
> [13439.455250] [<ffffffffa0462e42>] check_new_map+0x352/0x500 [ceph]
> [13439.461534] [<ffffffffa04631ad>] ceph_mdsc_handle_map+0x1bd/0x260 [ceph]
> [13439.468432] [<ffffffff814ebc7e>] ? mutex_unlock+0xe/0x10
> [13439.473934] [<ffffffffa043c612>] extra_mon_dispatch+0x22/0x30 [ceph]
> [13439.480464] [<ffffffffa03f6c2c>] dispatch+0xbc/0x110 [libceph]
> [13439.486492] [<ffffffffa03eec3d>] process_message+0x1ad/0x1d0 [libceph]
> [13439.493190] [<ffffffffa03f1498>] ? read_partial_message+0x3e8/0x520 [libceph]
> [13439.500583] [<ffffffff81415184>] ? kernel_recvmsg+0x44/0x60
> [13439.506324] [<ffffffffa03ef3a8>] ? ceph_tcp_recvmsg+0x48/0x60 [libceph]
> [13439.513140] [<ffffffffa03f2aae>] try_read+0x5fe/0x7e0 [libceph]
> [13439.519246] [<ffffffffa03f39f8>] con_work+0x378/0x4a0 [libceph]
> [13439.525345] [<ffffffff8107792f>] ? finish_task_switch+0x3f/0x110
> [13439.531515] [<ffffffff81060a95>] process_one_work+0x2b5/0x480
> [13439.537439] [<ffffffff810609f8>] ? process_one_work+0x218/0x480
> [13439.543526] [<ffffffff81064185>] worker_thread+0x1f5/0x320
> [13439.549191] [<ffffffff81063f90>] ? manage_workers+0x170/0x170
> [13439.555102] [<ffffffff81069641>] kthread+0xe1/0xf0
> [13439.560075] [<ffffffff81069560>] ? __init_kthread_worker+0x70/0x70
> [13439.566419] [<ffffffff814f7edc>] ret_from_fork+0x7c/0xb0
> [13439.571918] [<ffffffff81069560>] ? __init_kthread_worker+0x70/0x70
> [13439.587132] ceph: mds0 reconnect success
> [13490.720032] ceph: mds0 caps stale
> [13501.235257] ceph: mds0 recovery completed
> [13501.300419] ceph: mds0 caps renewed
>
> Fix it up by encoding locks into a buffer first, and when the
> number of encoded locks is stable, copy that into a ceph_pagelist.
>
> Signed-off-by: Jim Schutt <jaschut@...dia.gov>
> ---
> fs/ceph/locks.c | 76 +++++++++++++++++++++++++++++++-------------------
> fs/ceph/mds_client.c | 65 +++++++++++++++++++++++-------------------
> fs/ceph/super.h | 9 ++++-
> 3 files changed, 89 insertions(+), 61 deletions(-)
>
> diff --git a/fs/ceph/locks.c b/fs/ceph/locks.c
> index 4518313..8978851 100644
> --- a/fs/ceph/locks.c
> +++ b/fs/ceph/locks.c
> @@ -191,29 +191,23 @@ void ceph_count_locks(struct inode *inode, int *fcntl_count, int *flock_count)
> }
>
> /**
> - * Encode the flock and fcntl locks for the given inode into the pagelist.
> - * Format is: #fcntl locks, sequential fcntl locks, #flock locks,
> - * sequential flock locks.
> - * Must be called with lock_flocks() already held.
> - * If we encounter more of a specific lock type than expected,
> - * we return the value 1.
> + * Encode the flock and fcntl locks for the given inode into the ceph_filelock
> + * array. Must be called with lock_flocks() already held.
> + * If we encounter more of a specific lock type than expected, return -ENOSPC.
> */
> -int ceph_encode_locks(struct inode *inode, struct ceph_pagelist *pagelist,
> - int num_fcntl_locks, int num_flock_locks)
> +int ceph_encode_locks_to_buffer(struct inode *inode,
> + struct ceph_filelock *flocks,
> + int num_fcntl_locks, int num_flock_locks)
> {
> struct file_lock *lock;
> - struct ceph_filelock cephlock;
> int err = 0;
> int seen_fcntl = 0;
> int seen_flock = 0;
> - __le32 nlocks;
> + int l = 0;
>
> dout("encoding %d flock and %d fcntl locks", num_flock_locks,
> num_fcntl_locks);
> - nlocks = cpu_to_le32(num_fcntl_locks);
> - err = ceph_pagelist_append(pagelist, &nlocks, sizeof(nlocks));
> - if (err)
> - goto fail;
> +
> for (lock = inode->i_flock; lock != NULL; lock = lock->fl_next) {
> if (lock->fl_flags & FL_POSIX) {
> ++seen_fcntl;
> @@ -221,20 +215,12 @@ int ceph_encode_locks(struct inode *inode, struct ceph_pagelist *pagelist,
> err = -ENOSPC;
> goto fail;
> }
> - err = lock_to_ceph_filelock(lock, &cephlock);
> + err = lock_to_ceph_filelock(lock, &flocks[l]);
> if (err)
> goto fail;
> - err = ceph_pagelist_append(pagelist, &cephlock,
> - sizeof(struct ceph_filelock));
> + ++l;
> }
> - if (err)
> - goto fail;
> }
> -
> - nlocks = cpu_to_le32(num_flock_locks);
> - err = ceph_pagelist_append(pagelist, &nlocks, sizeof(nlocks));
> - if (err)
> - goto fail;
> for (lock = inode->i_flock; lock != NULL; lock = lock->fl_next) {
> if (lock->fl_flags & FL_FLOCK) {
> ++seen_flock;
> @@ -242,19 +228,51 @@ int ceph_encode_locks(struct inode *inode, struct ceph_pagelist *pagelist,
> err = -ENOSPC;
> goto fail;
> }
> - err = lock_to_ceph_filelock(lock, &cephlock);
> + err = lock_to_ceph_filelock(lock, &flocks[l]);
> if (err)
> goto fail;
> - err = ceph_pagelist_append(pagelist, &cephlock,
> - sizeof(struct ceph_filelock));
> + ++l;
> }
> - if (err)
> - goto fail;
> }
> fail:
> return err;
> }
>
> +/**
> + * Copy the encoded flock and fcntl locks into the pagelist.
> + * Format is: #fcntl locks, sequential fcntl locks, #flock locks,
> + * sequential flock locks.
> + * Returns zero on success.
> + */
> +int ceph_locks_to_pagelist(struct ceph_filelock *flocks,
> + struct ceph_pagelist *pagelist,
> + int num_fcntl_locks, int num_flock_locks)
> +{
> + int err = 0;
> + __le32 nlocks;
> +
> + nlocks = cpu_to_le32(num_fcntl_locks);
> + err = ceph_pagelist_append(pagelist, &nlocks, sizeof(nlocks));
> + if (err)
> + goto out_fail;
> +
> + err = ceph_pagelist_append(pagelist, flocks,
> + num_fcntl_locks * sizeof(*flocks));
> + if (err)
> + goto out_fail;
> +
> + nlocks = cpu_to_le32(num_flock_locks);
> + err = ceph_pagelist_append(pagelist, &nlocks, sizeof(nlocks));
> + if (err)
> + goto out_fail;
> +
> + err = ceph_pagelist_append(pagelist,
> + &flocks[num_fcntl_locks],
> + num_flock_locks * sizeof(*flocks));
> +out_fail:
> + return err;
> +}
> +
> /*
> * Given a pointer to a lock, convert it to a ceph filelock
> */
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index d9ca152..4d29203 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -2478,39 +2478,44 @@ static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
>
> if (recon_state->flock) {
> int num_fcntl_locks, num_flock_locks;
> - struct ceph_pagelist_cursor trunc_point;
> -
> - ceph_pagelist_set_cursor(pagelist, &trunc_point);
> - do {
> - lock_flocks();
> - ceph_count_locks(inode, &num_fcntl_locks,
> - &num_flock_locks);
> - rec.v2.flock_len = cpu_to_le32(2*sizeof(u32) +
> - (num_fcntl_locks+num_flock_locks) *
> - sizeof(struct ceph_filelock));
> - unlock_flocks();
> -
> - /* pre-alloc pagelist */
> - ceph_pagelist_truncate(pagelist, &trunc_point);
> - err = ceph_pagelist_append(pagelist, &rec, reclen);
> - if (!err)
> - err = ceph_pagelist_reserve(pagelist,
> - rec.v2.flock_len);
> -
> - /* encode locks */
> - if (!err) {
> - lock_flocks();
> - err = ceph_encode_locks(inode,
> - pagelist,
> - num_fcntl_locks,
> - num_flock_locks);
> - unlock_flocks();
> - }
> - } while (err == -ENOSPC);
> + struct ceph_filelock *flocks;
> +
> +encode_again:
> + lock_flocks();
> + ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
> + unlock_flocks();
> + flocks = kmalloc((num_fcntl_locks+num_flock_locks) *
> + sizeof(struct ceph_filelock), GFP_NOFS);
> + if (!flocks) {
> + err = -ENOMEM;
> + goto out_free;
> + }
> + lock_flocks();
> + err = ceph_encode_locks_to_buffer(inode, flocks,
> + num_fcntl_locks,
> + num_flock_locks);
> + unlock_flocks();
> + if (err) {
> + kfree(flocks);
> + if (err == -ENOSPC)
> + goto encode_again;
> + goto out_free;
> + }
> + /*
> + * number of encoded locks is stable, so copy to pagelist
> + */
> + rec.v2.flock_len = cpu_to_le32(2*sizeof(u32) +
> + (num_fcntl_locks+num_flock_locks) *
> + sizeof(struct ceph_filelock));
> + err = ceph_pagelist_append(pagelist, &rec, reclen);
> + if (!err)
> + err = ceph_locks_to_pagelist(flocks, pagelist,
> + num_fcntl_locks,
> + num_flock_locks);
> + kfree(flocks);
> } else {
> err = ceph_pagelist_append(pagelist, &rec, reclen);
> }
> -
> out_free:
> kfree(path);
> out_dput:
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index 8696be2..7ccfdb4 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -822,8 +822,13 @@ extern const struct export_operations ceph_export_ops;
> extern int ceph_lock(struct file *file, int cmd, struct file_lock *fl);
> extern int ceph_flock(struct file *file, int cmd, struct file_lock *fl);
> extern void ceph_count_locks(struct inode *inode, int *p_num, int *f_num);
> -extern int ceph_encode_locks(struct inode *i, struct ceph_pagelist *p,
> - int p_locks, int f_locks);
> +extern int ceph_encode_locks_to_buffer(struct inode *inode,
> + struct ceph_filelock *flocks,
> + int num_fcntl_locks,
> + int num_flock_locks);
> +extern int ceph_locks_to_pagelist(struct ceph_filelock *flocks,
> + struct ceph_pagelist *pagelist,
> + int num_fcntl_locks, int num_flock_locks);
> extern int lock_to_ceph_filelock(struct file_lock *fl, struct ceph_filelock *c);
>
> /* debugfs.c */
>
--
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