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| author | H. Peter Anvin <hpa@linux.intel.com> | 2016-02-10 13:47:06 -0800 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2016-02-10 13:50:18 -0800 |
| commit | 4e8501ccee8f7312a6c33475ece6255050a7ade4 (patch) | |
| tree | 19d93a741c7c460e96ca47489f522a101ddfdb5e /core/fs/getfssec.c | |
| parent | 7cd1ed60e37f36db859a2ca3d6ee261f98dafdac (diff) | |
| download | syslinux-4e8501ccee8f7312a6c33475ece6255050a7ade4.tar.gz syslinux-4e8501ccee8f7312a6c33475ece6255050a7ade4.tar.xz syslinux-4e8501ccee8f7312a6c33475ece6255050a7ade4.zip | |
getfssec: update comment explaining next_extent() semanticsobsolete-20160210
Update comments which explains next_extent() semantics to be slightly
clearer, and also correct the statement that next_extent can be NULL.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'core/fs/getfssec.c')
| -rw-r--r-- | core/fs/getfssec.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/core/fs/getfssec.c b/core/fs/getfssec.c index e099b64e..2ea122d9 100644 --- a/core/fs/getfssec.c +++ b/core/fs/getfssec.c @@ -39,18 +39,23 @@ * will store the initial sector number into inode->next_extent.lstart * on return.) * + * If inode->next_extent.pstart is EXTENT_ZERO, then no disk I/O is + * performed, and the data in the extent is all zero. + * * If inode->next_extent.len != 0 on entry then the routine is allowed * to assume inode->next_extent contains valid data from the previous * usage, which can be used for optimization purposes. * * If the filesystem can map the entire file as a single extent * (e.g. iso9660), then the filesystem can simply insert the extent - * information into inode->next_extent at searchdir/iget time, and leave - * next_extent() as NULL. + * information into inode->next_extent at searchdir/iget time, and point + * next_extent() to the generic function no_next_extent(). * * Note: the filesystem driver is not required to do extent coalescing, * if that is difficult to do; this routine will perform extent lookahead - * and coalescing. + * and coalescing. However, if the filesystem can do extent coalescing + * very cheaply by using filesystem-specific knowledge, then that is + * preferred (e.g. FAT). */ #include <dprintf.h> |