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Date: Mon, 18 Jan 2010 11:13:04 +0900 From: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Cc: Wu Fengguang <fengguang.wu@...el.com>, Andrew Morton <akpm@...ux-foundation.org>, Al Viro <viro@...iv.linux.org.uk>, Heiko Carstens <heiko.carstens@...ibm.com>, Christoph Hellwig <hch@...radead.org>, LKML <linux-kernel@...r.kernel.org>, Eric Paris <eparis@...hat.com>, Nick Piggin <npiggin@...e.de>, Andi Kleen <andi@...stfloor.org>, David Howells <dhowells@...hat.com>, Jonathan Corbet <corbet@....net>, <linux-fsdevel@...r.kernel.org> Subject: Re: [PATCH 6/6] vfs: introduce FMODE_NEG_OFFSET for allowing negative f_pos KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> writes: > On Mon, 18 Jan 2010 10:38:27 +0900 > OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> wrote: > >> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> writes: >> >> >> So, lseek() returns (uses) it? >> > >> > lseek can return negative value, as far as I know. >> >> Umm..., how do you know the difference of -EOVERFLOW and fpos == -75? >> > > Ah, sorry. I read wrong. > > For /dev/mem, it uses its own lseek function which allows negative f_pos > value. Other usual file system doesn't allow negative f_pos. > > It's ok not to return -EOVEFLOW for /dev/mem because there is no file end. No, no. I think it has the problem. E.g. /dev/mem returns -75 as fpos, so, lseek(2) returns -75 to userland. Then the userland (e.g. glibc) convert it as error. I.e. finally, errno == -75, and lseek(3) returns -1, right? Thanks. -- OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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