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author | Kirk McKusick <mckusick@FreeBSD.org> | 2020-12-06 20:50:21 +0000 |
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committer | Kirk McKusick <mckusick@FreeBSD.org> | 2020-12-06 20:50:21 +0000 |
commit | bb3c01ec7960a5eaff45916bd74446f96301c16d (patch) | |
tree | 9f8864d783b5fa95ed3ee6373aa0e3944f2f3cbe /sys/ufs | |
parent | 8fcfd0e2228de2c5b63d9c066d16a3f2a3b00cdb (diff) | |
download | src-bb3c01ec7960a5eaff45916bd74446f96301c16d.tar.gz src-bb3c01ec7960a5eaff45916bd74446f96301c16d.zip |
Document the BA_CLRBUF flag used in ufs and ext2fs filesystems.
Suggested by: kib
MFC after: 3 days
Sponsored by: Netflix
Notes
Notes:
svn path=/head/; revision=368396
Diffstat (limited to 'sys/ufs')
-rw-r--r-- | sys/ufs/ufs/ufs_extern.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/sys/ufs/ufs/ufs_extern.h b/sys/ufs/ufs/ufs_extern.h index cc6078065e7f..a28fcffabd2e 100644 --- a/sys/ufs/ufs/ufs_extern.h +++ b/sys/ufs/ufs/ufs_extern.h @@ -119,6 +119,13 @@ void softdep_revert_rmdir(struct inode *, struct inode *); * * Note: The general vfs code typically limits the sequential heuristic * count to 127. See sequential_heuristic() in kern/vfs_vnops.c + * + * The BA_CLRBUF flag specifies that the existing content of the block + * will not be completely overwritten by the caller, so buffers for new + * blocks must be cleared and buffers for existing blocks must be read. + * When BA_CLRBUF is not set the buffer will be completely overwritten + * and there is no reason to clear them or to spend I/O fetching existing + * data. The BA_CLRBUF flag is handled in the UFS_BALLOC() functions. */ #define BA_CLRBUF 0x00010000 /* Clear invalid areas of buffer. */ #define BA_METAONLY 0x00020000 /* Return indirect block buffer. */ |