On Tue, Jul 31, 2007 at 11:08:37PM +0100, Kostas Peletidis wrote: > Branden Sletteland wrote: > > I have also noticed this delay and have through instrumenting code > > have found that every block in the device gets read in. I never > > checked if it was something in the df, filesystem, SCSI, or USB > > subsystems that was causing this. I am usually doing df on USB > > storage devices formated as FAT 32 w/ and w/o LBA. > > > > Branden > > > > > Thanks for your reply Branden. This explains why df would delay for a > whole minute to terminate normally with a 500GB usb disk attached and > only for a second or two with a 512MB usb stick attached. Btw both are vfat. > > This brings another question though: Why read every single block during > the first run of df after the partition is mounted? Obviously buffering > 500GB for fast access is currently out of the question so could it be > the case that some sanity check was going on?
Probably the commit 28ec039c21839914389975b896160a815ffd8b83 is the
culprit:
fat: don't use free_clusters for fat32
It seems that the recent Windows changed specification, and it's
undocumented. Windows doesn't update ->free_clusters correctly.
This patch doesn't use ->free_clusters by default. (instead, add "usefree"
for forcing to use it)
Signed-off-by: OGAWA Hirofumi <[EMAIL PROTECTED]>
Cc: Juergen Beisert <[EMAIL PROTECTED]>
Cc: Andreas Schwab <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
You can add "usefree" to mount options - it will restore the old
behavior (which can apparently lead to wrong free space reports after
the disk has been used by some Windows versions). Without "usefree"
the vfat code in 2.6.22 will read the whole FAT to count free clusters
on the filesystem.
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