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

[Jaegeuk Kim <jaegeuk@kernel.org>]

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.

> 
> 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

> 
> 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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