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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?UqQ7rw48yElXJiZGDPhSkzhpdVp2IDp1VxOUJ9UuSzsbnBTzit8OIdTxjSeA?= =?us-ascii?Q?sdUuSZamHdAp9V2iGQwrXKvS8MxkO2xo5MRW72BgBEPvL+qOshVVDGYjeVn+?= =?us-ascii?Q?ofR1hmBoVJq4f1KUGjBXHWuYmIlj/6ikzlmFMhoqoJwZrCi1p1Mzaev1h2iF?= =?us-ascii?Q?+8/UYF5jwd407ZMf81Ls9RJvoZqOBqLJVT2ZTEsYpCa17QTDw8nD43UfQyDh?= =?us-ascii?Q?y/nwCl1zxZdlaukUXH2fCghFyU9Tm9tMl8IlWC48chnrgf0Y4tjy3uZmVWsn?= =?us-ascii?Q?TU++PfSs+in3vCRhFVXo/hagyegt0YoV002NOGHDtjCnKfAX3UvGGH+uSAOC?= =?us-ascii?Q?TAi8UUhs6fbtHfGEHX1sqIJBLQSRanh7tR+Tmh/sjnsZsTQYjP+ZCkH10tgZ?= =?us-ascii?Q?ykQSSJrPYqsu8nAZJ2O78+L92K8eiC8RaAmGbhXPofsMKjN1P+Nkpro3cP4V?= =?us-ascii?Q?6FgpGJlWKrhlWJ+sPuWddlxa06ttD8y7wdNbFiOu7HtuqSZk7Dpo/h6P/IJl?= =?us-ascii?Q?HxE0IhJVD+EQ5YFCYYFxWfA4oQDTVlguWIoCdpvKrikBpUIE3iKEpkPfqypr?= =?us-ascii?Q?AB76VJ+U3c44vrc2BURtlxMkoW+KHngDMD+snjSaDsARHFKJ2YcxLbHodY3Q?= =?us-ascii?Q?sl6wBZTHlexW/tXClIUCUtc1npg6D1lJ7KQpOAO8az7SubhzhHXLEJHOe/Js?= =?us-ascii?Q?12C98qoR/ll7/WEUeDcMo7Y1gG8YI3PcweVjFlYDEqCHIU4lvuq5B97fz5IL?= =?us-ascii?Q?xl/zJ6b08yMSOuiTv4nmbRjgLdEpSxhbDw5EQsYpsVCiHrHn98abaHp1Aeur?= =?us-ascii?Q?5xxvSGVeammtnMy60HZF3MfOh/GDVTDoaKiujFCkdk9Lq0zOD1IhpWo53rCJ?= =?us-ascii?Q?CW30bqbJn7rHv5WNui92SNC/rZshLXiOrddZmgbdq3PM3tgQfTR3KQp7wGU7?= =?us-ascii?Q?gEKxIbt3J24QD6TuKqXqjSUbzi7VKXXwGmNOB7W/K47UpnlHlqViIWNNbQ2G?= =?us-ascii?Q?oVq+cPqPDEXqJ6uCPu8UVXwG4TIuFe/xQCmsBu9q98r78F8+vEwSeNnfYEHI?= =?us-ascii?Q?381EEtKZNEPdcIPyD4FlFOdiZEn0dtOkZqUMPU+kD0tUgwQKPSFPiBce93mm?= =?us-ascii?Q?FxsBOEfzbHmMssYXpx12mJPvA7vqJek3DLSfVab4V7eSZRu/923ccyOfeEOS?= =?us-ascii?Q?WphhWaqwjUM9X0zeeMwDtCH2y4pxnuiBXsAfCr68tYlG1aab/C+4uvRiqqzL?= =?us-ascii?Q?o7TQ/xa5FaOcWkf2lg4K2XJ1enGsciapiaWQZHUgjpiI768SywPoKmC0CtVA?= =?us-ascii?Q?NpGpgQy5v5zn5f0T2GkAQW1vO4MkTG/1zKKM07MWNxBw/SvsChB/1uBtSZbH?= =?us-ascii?Q?ORv7sJGvpAXchkHKhO63ye7zl0GjH7b0Qmh4fGQ+LTaOo44j+3tu8fr0WtQ2?= =?us-ascii?Q?hU5HF7NP75i9TGEJnXSAr8kTv7yjWXcobXO/738KiJY47E6PdXOE7sZXAvVj?= =?us-ascii?Q?3Q24TYf4nuJtxqqT8NumX4woFtrzrfkJjfrg9dc2LBkRF/3ADVkxNCjqOfS2?= =?us-ascii?Q?H7WZiv0PnYnMCm02tjYBwaDZqzJZrxIyeFxdVtb68E3C8Aw04Ju7zrUajldd?= =?us-ascii?Q?Aw=3D=3D?= X-OriginatorOrg: hammerspace.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7dc521ca-de31-40e4-f684-08de276be0a4 X-MS-Exchange-CrossTenant-AuthSource: SN6PR13MB2365.namprd13.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Nov 2025 13:02:21.8056 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 0d4fed5c-3a70-46fe-9430-ece41741f59e X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: qaxPt4rTOl66b1X3QX7TGNq6aIH9XD1aacYu5A3avExmgE4DbFr9NtzDg9Ciew5XL2gITRTVNub7wrD7xsDkTlryZCv7YBCtzWGyWu7G5vQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR13MB5578 On 18 Nov 2025, at 20:41, NeilBrown wrote: > On Wed, 19 Nov 2025, Benjamin Coddington wrote: >> While knfsd offers combined exclusive create and open results to clients, >> on some filesystems those results may not be atomic. This behavior can be >> observed. For example, an open O_CREAT with mode 0 will succeed in creating >> the file but unexpectedly return -EACCES from vfs_open(). >> >> Additionally reducing the number of remote RPC calls required for O_CREAT >> on network filesystem provides a performance benefit in the open path. >> >> Teach knfsd's helper create_dentry() to use atomic_open() for filesystems >> that support it. >> >> Signed-off-by: Benjamin Coddington >> --- >> fs/namei.c | 43 ++++++++++++++++++++++++++++++++++++------- >> fs/nfsd/nfs4proc.c | 8 +++++--- >> include/linux/fs.h | 2 +- >> 3 files changed, 42 insertions(+), 11 deletions(-) >> >> diff --git a/fs/namei.c b/fs/namei.c >> index 9c0aad5bbff7..70ab74fb5e95 100644 >> --- a/fs/namei.c >> +++ b/fs/namei.c >> @@ -4208,21 +4208,50 @@ EXPORT_SYMBOL(user_path_create); >> * On success, returns a "struct file *". Otherwise a ERR_PTR >> * is returned. >> */ >> -struct file *dentry_create(const struct path *path, int flags, umode_t mode, >> +struct file *dentry_create(struct path *path, int flags, umode_t mode, > > I don't like that you dropped "const" without telling us why. > It is because we not assign to path->dentry, which is because > atomic_open() returns a dentry.... which will only be different for > directories (I think). > > But do we need to update path? The returned file will point to the > correct dentry - isn't that all that matters? > > I guess that I'd like an explanation for why the const is being dropped, > and why 'path' is being changed. Well, the first reason was that I was embarrassed at all the new local variables being added and atomic_open() wanted path->parent and dentry_create() already had path->child, it was convenient to just re-use it. Then it became clear that nfsd4_create_file() really wants to clean up (or not) the reference to its "child" dentry based on whether the dentry had been consumed or was an error - so passing back that dentry rather than re-arrange the tail of nfsd4_create_file() seemed nicer. Its true that we can acquire the dentry from file->f_path.dentry, but only in the successful case for both the atomic_open() and the vfs_create()/vfs_open() path. Atomic_open() does the work of swapping and fiddling with the dentry refcounts for us so we don't need to check, so that is the 2nd reason I passed the dentry back on struct path. I don't understand the cases atomic_open() is handling here: 3555 static struct dentry *atomic_open(const struct path *path, struct dentry *dentry, ... 3568 if (!error) { 3569 if (file->f_mode & FMODE_OPENED) { 3570 if (unlikely(dentry != file->f_path.dentry)) { 3571 dput(dentry); 3572 dentry = dget(file->f_path.dentry); 3573 } You think this can only happen for a directory? I figured VFS trying to work around whatever might have happened inside the filesystem. One thing that's not happening is that if knfsd /does/ get a different dentry back, its not updating struct svc_fh->fh_dentry. Ben