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author | H. Peter Anvin <hpa@linux.intel.com> | 2016-02-10 13:47:06 -0800 |
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committer | H. Peter Anvin <hpa@linux.intel.com> | 2016-02-17 15:25:11 -0800 |
commit | c1cc1bcef1e23ecb9f650c75f9dafc7e61101218 (patch) | |
tree | 8cce24c16b9eb37ae8f453d444fe4c41a9b12f4a | |
parent | 875001667b9cbb1af421ce3e84feb8ce548dc5e4 (diff) | |
download | syslinux-c1cc1bcef1e23ecb9f650c75f9dafc7e61101218.tar.gz |
getfssec: update comment explaining next_extent() semantics
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>
-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> |