Re: [f2fs-dev] [PATCH v2] mkfs.f2fs: check zeros in first 16MB for Android

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 08/16, Chao Yu wrote:
> On 2019/8/16 6:21, Jaegeuk Kim wrote:
> > On 08/12, Chao Yu wrote:
> >> On 2019/8/9 23:12, Jaegeuk Kim wrote:
> >>> We actually don't need to issue trim on entire disk by checking first
> >>> blocks having zeros.
> >>
> >> In heap mode, we locate node log header to tail end of device, should we
> >> consider to check block contain according to heap option?
> > 
> > I wanted to check F2FS metadata mainly.
> 
> Oh, I thought you mean main area. :P
> 
> > 
> >>
> >> BTW, if we changed cp_ver whenever mkfs, why should we still issue trim to
> >> obsolete old data in node remained in image?
> > 
> > For simplicity. :P
> 
> I didn't get why we can assume all metadata are zeroed if first 16MB are all zero...
> 
> BTW, if first 16MB are non-zero, why not just trim F2FS metadata rather than
> whole area?

Trim the entire space so that we can skip discard in runtime by the flag, right?

> 
> Thanks,
> 
> > 
> >>
> >> Thanks,
> >>
> >>>
> >>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> >>> ---
> >>> v2 from v1:
> >>>  - clean up
> >>>
> >>>  mkfs/f2fs_format_utils.c | 53 ++++++++++++++++++++++++++++++++++++++--
> >>>  1 file changed, 51 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/mkfs/f2fs_format_utils.c b/mkfs/f2fs_format_utils.c
> >>> index 8bf128c..f2d55ad 100644
> >>> --- a/mkfs/f2fs_format_utils.c
> >>> +++ b/mkfs/f2fs_format_utils.c
> >>> @@ -25,6 +25,7 @@
> >>>  #include <stdio.h>
> >>>  #include <unistd.h>
> >>>  #include <stdlib.h>
> >>> +#include <stdbool.h>
> >>>  #ifndef ANDROID_WINDOWS_HOST
> >>>  #include <sys/ioctl.h>
> >>>  #endif
> >>> @@ -110,13 +111,61 @@ static int trim_device(int i)
> >>>  	return 0;
> >>>  }
> >>>  
> >>> +static bool is_wiped_device(int i)
> >>> +{
> >>> +#ifdef WITH_ANDROID
> >>> +	struct device_info *dev = c.devices + i;
> >>> +	int fd = dev->fd;
> >>> +	char *buf, *zero_buf;
> >>> +	bool wiped = true;
> >>> +	int nblocks = 4096;	/* 16MB size */
> >>> +	int j;
> >>> +
> >>> +	buf = malloc(F2FS_BLKSIZE);
> >>> +	if (buf == NULL) {
> >>> +		MSG(1, "\tError: Malloc Failed for buf!!!\n");
> >>> +		return false;
> >>> +	}
> >>> +	zero_buf = calloc(1, F2FS_BLKSIZE);
> >>> +	if (zero_buf == NULL) {
> >>> +		MSG(1, "\tError: Calloc Failed for zero buf!!!\n");
> >>> +		free(buf);
> >>> +		return false;
> >>> +	}
> >>> +
> >>> +	if (lseek(fd, 0, SEEK_SET) < 0) {
> >>> +		free(zero_buf);
> >>> +		free(buf);
> >>> +		return false;
> >>> +	}
> >>> +
> >>> +	/* check first n blocks */
> >>> +	for (j = 0; j < nblocks; j++) {
> >>> +		if (read(fd, buf, F2FS_BLKSIZE) != F2FS_BLKSIZE ||
> >>> +				memcmp(buf, zero_buf, F2FS_BLKSIZE)) {
> >>> +			wiped = false;
> >>> +			break;
> >>> +		}
> >>> +	}
> >>> +	free(zero_buf);
> >>> +	free(buf);
> >>> +
> >>> +	if (wiped)
> >>> +		MSG(0, "Info: Found all zeros in first %d blocks\n", nblocks);
> >>> +	return wiped;
> >>> +#else
> >>> +	return false;
> >>> +#endif
> >>> +}
> >>> +
> >>>  int f2fs_trim_devices(void)
> >>>  {
> >>>  	int i;
> >>>  
> >>> -	for (i = 0; i < c.ndevs; i++)
> >>> -		if (trim_device(i))
> >>> +	for (i = 0; i < c.ndevs; i++) {
> >>> +		if (!is_wiped_device(i) && trim_device(i))
> >>>  			return -1;
> >>> +	}
> >>>  	c.trimmed = 1;
> >>>  	return 0;
> >>>  }
> >>>
> > .
> > 


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