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[209.85.208.47]) by smtp.gmail.com with ESMTPSA id d23-20020a056402079700b00559c71e70e3sm1930970edy.79.2024.01.27.12.01.43 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 27 Jan 2024 12:01:43 -0800 (PST) Received: by mail-ed1-f47.google.com with SMTP id 4fb4d7f45d1cf-55a90b2b554so1653649a12.1 for ; Sat, 27 Jan 2024 12:01:43 -0800 (PST) X-Received: by 2002:a05:6402:3137:b0:55e:b30c:e0db with SMTP id dd23-20020a056402313700b0055eb30ce0dbmr1269613edb.35.1706385702705; Sat, 27 Jan 2024 12:01:42 -0800 (PST) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240126150209.367ff402@gandalf.local.home> <20240126162626.31d90da9@gandalf.local.home> <9b34c04465ff46dba90c81b4240fbbd1@AcuMS.aculab.com> In-Reply-To: <9b34c04465ff46dba90c81b4240fbbd1@AcuMS.aculab.com> From: Linus Torvalds Date: Sat, 27 Jan 2024 12:01:26 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] eventfs: Have inodes have unique inode numbers To: David Laight Cc: Steven Rostedt , LKML , Linux Trace Devel , Masami Hiramatsu , Mathieu Desnoyers , Christian Brauner , Ajay Kaher , Geert Uytterhoeven , linux-fsdevel Content-Type: text/plain; charset="UTF-8" On Sat, 27 Jan 2024 at 07:27, David Laight wrote: > > Doesn't Linux support 64bit inode numbers? > They solve the wrap problem... Yes, but we've historically had issues with actually exposing them. The legacy stat() code has things like this: tmp.st_ino = stat->ino; if (sizeof(tmp.st_ino) < sizeof(stat->ino) && tmp.st_ino != stat->ino) return -EOVERFLOW; so if you have really old 32-bit user space, you generally do not actually want to have 64-bit inode numbers. This is why "get_next_ino()" returns a strictly 32-bit only inode number. You don't want to error out on a 'fstat()' just because you're on a big system that has been running for a long time. Now, 'stat64' was introduced for this reason back in 2.3.34, so back in 1999. So any half-way modern 32-bit environment doesn't have that issue, and maybe it's time to just sunset all the old stat() calls. Of course, the *really* old stat has a 16-bit inode number. Search for __old_kernel_stat to still see that. That's more of a curiosity than anything else. Linus