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Document the BA_CLRBUF flag used in ufs and ext2fs filesystems.

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Suggested by: kib
MFC after:    3 days
Sponsored by: Netflix
This commit is contained in:
Kirk McKusick 2020-12-06 20:50:21 +00:00
parent 8fcfd0e222
commit bb3c01ec79
2 changed files with 14 additions and 0 deletions
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7
sys/fs/ext2fs/ext2_extern.h
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@ -135,6 +135,13 @@ void ext2_gd_csum_set(struct m_ext2fs *);
/* Flags to low-level allocation routines.
* The low 16-bits are reserved for IO_ flags from vnode.h.
*
* 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_SEQMASK 0x7F000000 /* Bits holding seq heuristic. */

7
sys/ufs/ufs/ufs_extern.h
View file

@ -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. */