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Date: Sun, 4 May 2014 09:04:00 +0200 From: Michael Kerrisk <mtk.manpages@...il.com> To: George Spelvin <linux@...izon.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Linux-Fsdevel <linux-fsdevel@...r.kernel.org>, Linux Kernel <linux-kernel@...r.kernel.org>, Al Viro <viro@...iv.linux.org.uk>, Michael Kerrisk-manpages <mtk.manpages@...il.com> Subject: Re: Update of file offset on write() etc. is non-atomic with I/O Ouch! I've just seen that trimming the CC on this reply took me out of a large part of the subsequent conversation. PLEASE don't trim CCs, and especially not the address of the OP!! On Mon, Mar 3, 2014 at 10:03 PM, George Spelvin <linux@...izon.com> wrote: >> struct fd { >> struct file *file; >> - int need_put; >> + unsigned need_put:1, need_pos_unlock:1; >> }; > > Since we're rounding up to 2*sizeof(struct file *) anyway, is this a case > where wasting space on a couple of char (or bool) flags would generate > better code than a bitfield? > > In particular, the code to set need_pos_unlock (which will be executed > each read/write for most files) is messy in the bitfield case. > A byte store is much cleaner. > > (If you want to use bits, why not use the two lsbits of the file pointer > for the purpose? That would save a lot of space.) > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface", http://blog.man7.org/ -- 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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