3 .\" Copyright (c) 1996 Doug Rabson
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37 .Nd read or write a file
43 .Fn VOP_READ "struct vnode *vp" "struct uio *uio" "int ioflag" "struct ucred *cred"
45 .Fn VOP_WRITE "struct vnode *vp" "struct uio *uio" "int ioflag" "struct ucred *cred"
47 These entry points read or write the contents of a file
50 .Bl -tag -width ioflag
52 The vnode of the file.
54 The location of the data to be read or written.
58 The credentials of the caller.
63 argument is used to give directives and hints to the file system.
64 When attempting a read, the high 16 bits are used to provide a
65 read-ahead hint (in units of file system blocks) that the file system
67 The low 16 bits are a bit mask which can contain
69 .Bl -tag -width ".Dv IO_NODELOCKED"
71 Do I/O as atomic unit.
77 Underlying node already locked.
80 flag set in file table.
82 Data already in VMIO space.
85 The file should be locked on entry and will still be locked on exit.
87 Zero is returned on success, otherwise an error code is returned.
91 vop_read(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
96 long size, xfersize, blkoffset;
99 size = block size of file system;
101 for (error = 0, bp = NULL; uio->uio_resid > 0; bp = NULL) {
102 bytesinfile = size of file - uio->uio_offset;
103 if (bytesinfile <= 0)
106 lbn = uio->uio_offset / size;
107 blkoffset = uio->uio_offset - lbn * size;
109 xfersize = size - blkoffset;
110 if (uio->uio_resid < xfersize)
111 xfersize = uio->uio_resid;
112 if (bytesinfile < xfersize)
113 xfersize = bytesinfile;
115 error = bread(vp, lbn, size, NOCRED, &bp);
123 * We should only get non-zero b_resid when an I/O error
124 * has occurred, which should cause us to break above.
125 * However, if the short read did not cause an error,
126 * then we want to ensure that we do not uiomove bad
127 * or uninitialized data.
130 if (size < xfersize) {
136 error = uiomove((char *)bp->b_data + blkoffset, (int)xfersize, uio);
149 vop_write(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
153 daddr_t lbn, nextlbn;
155 long size, resid, xfersize, blkoffset;
159 osize = size of file;
160 size = block size of file system;
161 resid = uio->uio_resid;
162 if (ioflag & IO_SYNC)
167 for (error = 0; uio->uio_resid > 0;) {
168 lbn = uio->uio_offset / size;
169 blkoffset = uio->uio_offset - lbn * size;
171 xfersize = size - blkoffset;
172 if (uio->uio_resid < xfersize)
173 xfersize = uio->uio_resid;
175 if (uio->uio_offset + xfersize > size of file)
176 vnode_pager_setsize(vp, uio->uio_offset + xfersize);
183 error = find_block_in_file(vp, lbn, blkoffset + xfersize,
188 if (uio->uio_offset + xfersize > size of file)
189 set size of file to uio->uio_offset + xfersize;
191 error = uiomove((char *)bp->b_data + blkoffset, (int) xfersize, uio);
192 /* XXX ufs does not check the error here. Why? */
194 if (ioflag & IO_VMIO)
195 bp->b_flags |= B_RELBUF; /* ??? */
197 if (ioflag & IO_SYNC)
199 else if (xfersize + blkoffset == size)
204 if (error || xfersize == 0)
209 if (ioflag & IO_UNIT) {
210 /* call private routine to truncate file. */
211 your_truncate(vp, osize, ioflag & IO_SYNC, cred, uio->uio_td);
212 uio->uio_offset -= resid - uio->uio_resid;
213 uio->uio_resid = resid;
215 } else if (resid > uio->uio_resid && (ioflag & IO_SYNC)) {
217 error = VOP_UPDATE(vp, &tv, &tv, 1); /* XXX what does this do? */
226 An attempt was made to write a file that exceeds the process's file size
227 limit or the maximum file size.
229 The file system is full.
231 An append-only flag is set on the file, but the caller is attempting to
232 write before the current end of file.
238 This man page was written by