Badari Pulavarty wrote:
BTW, what is the interface for finding out what is the size of the
pre-allocated file ?
With XFS at least, "du," "stat," etc tell you a little:
[root@magnesium test]# touch resvsp
[root@magnesium test]# xfs_io resvsp
xfs_io> resvsp 0 10g
The file is 0 length, but is using 10g of blocks:
(with posix_fallocate this would move the size out to 10g as well)
[root@magnesium test]# ls -lh resvsp
-rw-r--r-- 1 root root 0 Nov 28 14:11 resvsp
[root@magnesium test]# du -hc resvsp
10G resvsp
10G total
[root@magnesium test]# stat resvsp
File: `resvsp'
Size: 0 Blocks: 20971520 IO Block: 4096 regular
empty file
Device: 81eh/2078d Inode: 186 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
xfs also has an interface to find out what allocations are where:
if you reserve some ranges not starting at 0...
[root@magnesium test]# xfs_io resvsp
xfs_io> resvsp 1g 1g
xfs_io> resvsp 3g 1g
xfs_io> resvsp 5g 1g
xfs_io> quit
[root@magnesium test]# xfs_bmap -v resvsp
resvsp:
EXT: FILE-OFFSET BLOCK-RANGE AG AG-OFFSET
TOTAL FLAGS
0: [0..2097151]: hole
2097152
1: [2097152..4194303]: 42392..2139543 0 (42392..2139543)
2097152 10000
2: [4194304..6291455]: hole
2097152
3: [6291456..8388607]: 4236696..6333847 0 (4236696..6333847)
2097152 10000
4: [8388608..10485759]: hole
2097152
5: [10485760..12582911]: 8431000..10528151 0 (8431000..10528151)
2097152 10000
The flags of 10000 mean that these extents is preallocated/unwritten.
I suppose outside of XFS, FIBMAP is your best bet, but that won't tell
you what is preallocated vs. allocated/written....
-Eric
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