On 6/16/16, 21:11, "Oleg Drokin" <green@xxxxxxxxxxxxxx> wrote:
I get almost-insta-crash with this patch (really, just testing
the testing branch, but in the code this patch introduced).
-rc2 did not have this sort of crash, so it must be a new one.
On Jun 14, 2016, at 3:05 PM, Trond Myklebust wrote:
> Unless the user is using file locking, we must assume close-to-open
> cache consistency when the file is open for writing. Adjust the
> caching algorithm so that it does not clear the cache on out-of-order
> writes and/or attribute revalidations.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> fs/nfs/file.c | 13 ++-----------
> fs/nfs/inode.c | 56 +++++++++++++++++++++++++++++++++++++++-----------------
> 2 files changed, 41 insertions(+), 28 deletions(-)
>
> diff --git a/fs/nfs/file.c b/fs/nfs/file.c
> index 717a8d6af52d..2d39d9f9da7d 100644
> --- a/fs/nfs/file.c
> +++ b/fs/nfs/file.c
> @@ -780,11 +780,6 @@ do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
> }
>
> static int
> -is_time_granular(struct timespec *ts) {
> - return ((ts->tv_sec == 0) && (ts->tv_nsec <= 1000));
> -}
> -
> -static int
> do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
> {
> struct inode *inode = filp->f_mapping->host;
> @@ -817,12 +812,8 @@ do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
> * This makes locking act as a cache coherency point.
> */
> nfs_sync_mapping(filp->f_mapping);
> - if (!NFS_PROTO(inode)->have_delegation(inode, FMODE_READ)) {
> - if (is_time_granular(&NFS_SERVER(inode)->time_delta))
> - __nfs_revalidate_inode(NFS_SERVER(inode), inode);
> - else
> - nfs_zap_caches(inode);
> - }
> + if (!NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
> + nfs_zap_mapping(inode, filp->f_mapping);
> out:
> return status;
> }
> diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> index 60051e62d3f1..8a808d25dbc8 100644
> --- a/fs/nfs/inode.c
> +++ b/fs/nfs/inode.c
> @@ -878,7 +878,10 @@ void nfs_inode_attach_open_context(struct nfs_open_context *ctx)
> struct nfs_inode *nfsi = NFS_I(inode);
>
> spin_lock(&inode->i_lock);
> - list_add(&ctx->list, &nfsi->open_files);
> + if (ctx->mode & FMODE_WRITE)
> + list_add(&ctx->list, &nfsi->open_files);
> + else
> + list_add_tail(&ctx->list, &nfsi->open_files);
> spin_unlock(&inode->i_lock);
> }
> EXPORT_SYMBOL_GPL(nfs_inode_attach_open_context);
> @@ -1215,6 +1218,21 @@ int nfs_revalidate_mapping_protected(struct inode *inode, struct address_space *
> return __nfs_revalidate_mapping(inode, mapping, true);
> }
>
> +static bool nfs_file_has_writers(struct nfs_inode *nfsi)
> +{
> + assert_spin_locked(&nfsi->vfs_inode.i_lock);
> +
> + if (list_empty(&nfsi->open_files))
> + return false;
> + /* Note: This relies on nfsi->open_files being ordered with writers
> + * being placed at the head of the list.
> + * See nfs_inode_attach_open_context()
> + */
> + return (list_first_entry(&nfsi->open_files,
> + struct nfs_open_context,
> + list)->mode & FMODE_WRITE) == FMODE_WRITE;
> +}
> +
> static unsigned long nfs_wcc_update_inode(struct inode *inode, struct nfs_fattr *fattr)
> {
> struct nfs_inode *nfsi = NFS_I(inode);
> @@ -1279,22 +1297,24 @@ static int nfs_check_inode_attributes(struct inode *inode, struct nfs_fattr *fat
> if ((fattr->valid & NFS_ATTR_FATTR_TYPE) && (inode->i_mode & S_IFMT) != (fattr->mode & S_IFMT))
> return -EIO;
>
> - if ((fattr->valid & NFS_ATTR_FATTR_CHANGE) != 0 &&
> - inode->i_version != fattr->change_attr)
> - invalid |= NFS_INO_INVALID_ATTR|NFS_INO_REVAL_PAGECACHE;
> + if (!nfs_file_has_writers(nfsi)) {
The crash address points here ^^:
gdb> l *(nfs_refresh_inode_locked+0x249)
0xffffffff81382c39 is in nfs_refresh_inode_locked (/home/green/bk/linux-test/fs/nfs/inode.c:1301).
1301 if (!nfs_file_has_writers(nfsi)) {
Did some racing thread just kill the inode under this thread I wonder?
[ 264.739757] BUG: unable to handle kernel paging request at ffff88009875ffe8
[ 264.740468] IP: [<ffffffff81382c39>] nfs_refresh_inode_locked+0x249/0x4e0
[ 264.741080] PGD 3580067 PUD 3583067 PMD bce56067 PTE 800000009875f060
[ 264.741836] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC
[ 264.742357] Modules linked in: loop rpcsec_gss_krb5 acpi_cpufreq tpm_tis joydev tpm virtio_console pcspkr i2c_piix4 nfsd ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm floppy serio_raw
[ 264.785009] CPU: 7 PID: 34494 Comm: ls Not tainted 4.7.0-rc3-vm-nfs+ #2
[ 264.785559] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.2-20150714_191134- 04/01/2014
[ 264.786545] task: ffff88009f78cac0 ti: ffff88009f780000 task.ti: ffff88009f780000
[ 264.787596] RIP: 0010:[<ffffffff81382c39>] [<ffffffff81382c39>] nfs_refresh_inode_locked+0x249/0x4e0
[ 264.788628] RSP: 0018:ffff88009f783b58 EFLAGS: 00010246
[ 264.789151] RAX: 0000000000000000 RBX: ffff8800aa48b348 RCX: ffff880098760000
[ 264.789708] RDX: 0000000000027e7f RSI: 0000000000000001 RDI: ffff8800aa48b348
[ 264.792533] RBP: ffff88009f783b70 R08: 0000000000000000 R09: 0000000000000001
[ 264.793090] R10: ffff8800aa48b3e8 R11: 0000000000000000 R12: ffff8800aa48b348
[ 264.793647] R13: ffff880093f8cf00 R14: ffff880089eb10c0 R15: ffff88009f783de0
[ 264.794204] FS: 00007fefee488800(0000) GS:ffff8800b9000000(0000) knlGS:0000000000000000
[ 264.795154] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 264.795686] CR2: ffff88009875ffe8 CR3: 000000009f3ab000 CR4: 00000000000006e0
[ 264.796243] Stack:
[ 264.796708] ffff8800aa48b3d0 ffff8800aa48b348 ffff880093f8cf00 ffff88009f783b98
[ 264.797853] ffffffff81382efe ffff8800aa48b348 ffff88009f783c38 0000000000000000
[ 264.798996] ffff88009f783ba8 ffffffff81382f39 ffff88009f783c18 ffffffff81396fe3
[ 264.824881] Call Trace:
[ 264.825366] [<ffffffff81382efe>] nfs_refresh_inode.part.24+0x2e/0x50
[ 264.825908] [<ffffffff81382f39>] nfs_refresh_inode+0x19/0x20
[ 264.826441] [<ffffffff81396fe3>] nfs3_proc_access+0xd3/0x190
[ 264.826971] [<ffffffff8137c66c>] nfs_do_access+0x3ec/0x620
[ 264.837497] [<ffffffff8137c2d1>] ? nfs_do_access+0x51/0x620
I suspect this is the bug that the automated testing also found with the nfs_revalidate_inode() getting called as part of the RCU path. I have a new patch series that fixes that issue and that I’ll publish soon (just need to figure out what to do about the last few comments from Christoph’s review).
Cheers
Trond
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