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ext2: do not load entire directories into memory when doing directory operations

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Matheus
2025-09-01 21:39:29 -03:00
parent 6a2e83cc49
commit 59d040e177
1 changed files with 52 additions and 44 deletions
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kernel-src/fs/ext2.c
+52 -44
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@@ -879,36 +879,41 @@ static int rwbytes(ext2fs_t *fs, ext2node_t *node, void *buffer, size_t count, u
#define BUFFER_MAP_FLAGS (ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_WRITE | ARCH_MMU_FLAGS_NOEXEC) #define BUFFER_MAP_FLAGS (ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_WRITE | ARCH_MMU_FLAGS_NOEXEC)
// returns the inode in inode
// if switchnode is non null, switches the found dent to point to that inode (such as on a rename)
static int findindir(ext2fs_t *fs, ext2node_t *node, char *name, int *inode, ext2node_t *switchnode) { static int findindir(ext2fs_t *fs, ext2node_t *node, char *name, int *inode, ext2node_t *switchnode) {
// XXX loading the whole dir into memory at once isn't the best idea but works for now void *dirbuffer = alloc(fs->blocksize);
void *dirbuffer = vmm_map(NULL, INODE_SIZE(&node->inode) + 1, VMM_FLAGS_ALLOCATE, BUFFER_MAP_FLAGS, NULL); // + 1 to make sure there is at least one page mapped
if (dirbuffer == NULL) if (dirbuffer == NULL)
return ENOMEM; return ENOMEM;
int err = rwbytes(fs, node, dirbuffer, INODE_SIZE(&node->inode), 0, false, true); int err;
if (err) size_t size = INODE_SIZE(&node->inode);
goto cleanup; size_t bytes_done = 0;
uintmax_t offset = 0;
int inodefound = 0; int inodefound = 0;
size_t namelen = strlen(name); size_t namelen = strlen(name);
// iterate through directory to find the inode number while (bytes_done < size) {
while (offset < INODE_SIZE(&node->inode)) { size_t block_offset = bytes_done % fs->blocksize;
ext2dent_t *dent = (ext2dent_t *)((uintptr_t)dirbuffer + offset); if (block_offset == 0) {
err = rwbytes(fs, node, dirbuffer, fs->blocksize, bytes_done, false, true);
if (err)
goto cleanup;
}
ext2dent_t *dent = (ext2dent_t *)((uintptr_t)dirbuffer + block_offset);
if (namelen == dent->namelen && dent->inode && strncmp(name, dent->name, dent->namelen) == 0) { if (namelen == dent->namelen && dent->inode && strncmp(name, dent->name, dent->namelen) == 0) {
inodefound = dent->inode; inodefound = dent->inode;
if (switchnode) { if (switchnode) {
dent->inode = switchnode->id; dent->inode = switchnode->id;
dent->type = vfstoext2denttypetable[switchnode->vnode.type]; dent->type = vfstoext2denttypetable[switchnode->vnode.type];
err = rwbytes(fs, node, dent, dent->size, offset, true, true); err = rwbytes(fs, node, dent, dent->size, bytes_done, true, true);
} }
break; break;
} }
__assert(dent->size); __assert(dent->size);
offset += dent->size; bytes_done += dent->size;
} }
if (inodefound == 0) if (inodefound == 0)
@@ -917,9 +922,7 @@ static int findindir(ext2fs_t *fs, ext2node_t *node, char *name, int *inode, ext
*inode = inodefound; *inode = inodefound;
cleanup: cleanup:
if (dirbuffer) free(dirbuffer);
vmm_unmap(dirbuffer, INODE_SIZE(&node->inode) + 1, 0);
return err; return err;
} }
@@ -936,21 +939,23 @@ static int insertdent(ext2fs_t *fs, ext2node_t *node, char *name, int inode, int
memcpy(dentbuffer->name, name, namelen); memcpy(dentbuffer->name, name, namelen);
size_t inodesize = INODE_SIZE(&node->inode); size_t inodesize = INODE_SIZE(&node->inode);
// XXX loading the whole dir into memory isn't the best idea void *dirbuffer = alloc(fs->blocksize);
void *dirbuffer = vmm_map(NULL, inodesize + 1, VMM_FLAGS_ALLOCATE, BUFFER_MAP_FLAGS, NULL); // + 1 to make sure there is at least one page mapped
int err = dirbuffer ? 0 : ENOMEM; int err = dirbuffer ? 0 : ENOMEM;
if (err) if (err)
goto cleanup; goto cleanup;
err = rwbytes(fs, node, dirbuffer, inodesize, 0, false, true);
if (err)
goto cleanup;
ext2dent_t *splitdent = NULL; ext2dent_t *splitdent = NULL;
uintmax_t offset = 0; uintmax_t offset = 0;
size_t truesize, freesize; size_t truesize, freesize;
while (offset < inodesize) { while (offset < inodesize) {
splitdent = (ext2dent_t *)((uintptr_t)dirbuffer + offset); size_t block_offset = offset % fs->blocksize;
if (block_offset == 0) {
err = rwbytes(fs, node, dirbuffer, fs->blocksize, offset, false, true);
if (err)
goto cleanup;
}
splitdent = (ext2dent_t *)((uintptr_t)dirbuffer + block_offset);
truesize = splitdent->inode == 0 ? 0 : ROUND_UP(sizeof(ext2dent_t) + splitdent->namelen, 4); truesize = splitdent->inode == 0 ? 0 : ROUND_UP(sizeof(ext2dent_t) + splitdent->namelen, 4);
freesize = splitdent->size - truesize; freesize = splitdent->size - truesize;
@@ -980,30 +985,34 @@ static int insertdent(ext2fs_t *fs, ext2node_t *node, char *name, int inode, int
cleanup: cleanup:
if (dirbuffer) if (dirbuffer)
vmm_unmap(dirbuffer, inodesize + 1, 0); free(dirbuffer);
free(dentbuffer); free(dentbuffer);
return err; return err;
} }
// TODO defrag dents in block
static int removedent(ext2fs_t *fs, ext2node_t *node, char *name, int *inode) { static int removedent(ext2fs_t *fs, ext2node_t *node, char *name, int *inode) {
// XXX loading the whole dir into memory at once isn't the best idea but works for now void *dirbuffer = alloc(fs->blocksize);
void *dirbuffer = vmm_map(NULL, INODE_SIZE(&node->inode) + 1, VMM_FLAGS_ALLOCATE, BUFFER_MAP_FLAGS, NULL); // + 1 to make sure there is at least one page mapped
if (dirbuffer == NULL) if (dirbuffer == NULL)
return ENOMEM; return ENOMEM;
int err = rwbytes(fs, node, dirbuffer, INODE_SIZE(&node->inode), 0, false, true);
if (err)
goto cleanup;
uintmax_t offset = 0; uintmax_t offset = 0;
int inodefound = 0; int inodefound = 0;
size_t namelen = strlen(name); size_t namelen = strlen(name);
uintmax_t lastsize = 0; uintmax_t lastsize = 0;
ext2dent_t *dent = NULL; ext2dent_t *dent = NULL;
int err;
// iterate through directory to find the inode number and dent offset // iterate through directory to find the inode number and dent offset
while (offset < INODE_SIZE(&node->inode)) { while (offset < INODE_SIZE(&node->inode)) {
dent = (ext2dent_t *)((uintptr_t)dirbuffer + offset); size_t block_offset = offset % fs->blocksize;
if (block_offset == 0) {
err = rwbytes(fs, node, dirbuffer, fs->blocksize, offset, false, true);
if (err)
goto cleanup;
}
dent = (ext2dent_t *)((uintptr_t)dirbuffer + block_offset);
if (namelen == dent->namelen && dent->inode && strncmp(name, dent->name, dent->namelen) == 0) { if (namelen == dent->namelen && dent->inode && strncmp(name, dent->name, dent->namelen) == 0) {
inodefound = dent->inode; inodefound = dent->inode;
@@ -1033,8 +1042,7 @@ static int removedent(ext2fs_t *fs, ext2node_t *node, char *name, int *inode) {
} }
cleanup: cleanup:
if (dirbuffer) free(dirbuffer);
vmm_unmap(dirbuffer, INODE_SIZE(&node->inode) + 1, 0);
return err; return err;
} }
@@ -1255,15 +1263,9 @@ static int ext2_getdents(vnode_t *vnode, dent_t *buffer, size_t count, uintmax_t
int err = 0; int err = 0;
// XXX loading the whole dir into memory at once isn't the best idea but works for now // XXX loading the whole dir into memory at once isn't the best idea but works for now
void *dirbuffer = vmm_map(NULL, INODE_SIZE(&node->inode) + 1, VMM_FLAGS_ALLOCATE, BUFFER_MAP_FLAGS, NULL); // + 1 to make sure there is at least one page mapped void *dirbuffer = alloc(fs->blocksize);
if (dirbuffer == NULL) { if (dirbuffer == NULL)
err = ENOMEM; return ENOMEM;
goto cleanup;
}
err = rwbytes(fs, node, dirbuffer, INODE_SIZE(&node->inode), 0, false, true);
if (err)
goto cleanup;
uintmax_t currdiroffset = 0; uintmax_t currdiroffset = 0;
uintmax_t offset = 0; uintmax_t offset = 0;
@@ -1271,7 +1273,14 @@ static int ext2_getdents(vnode_t *vnode, dent_t *buffer, size_t count, uintmax_t
// iterate through directory and build dent entries // iterate through directory and build dent entries
while (offset < INODE_SIZE(&node->inode) && i < count) { while (offset < INODE_SIZE(&node->inode) && i < count) {
ext2dent_t *dent = (ext2dent_t *)((uintptr_t)dirbuffer + offset); size_t block_offset = offset % fs->blocksize;
if (block_offset == 0) {
err = rwbytes(fs, node, dirbuffer, fs->blocksize, offset, false, true);
if (err)
goto cleanup;
}
ext2dent_t *dent = (ext2dent_t *)((uintptr_t)dirbuffer + block_offset);
if (dent->inode && currdiroffset++ >= diroffset) { if (dent->inode && currdiroffset++ >= diroffset) {
buffer[i].d_ino = dent->inode; buffer[i].d_ino = dent->inode;
@@ -1289,8 +1298,7 @@ static int ext2_getdents(vnode_t *vnode, dent_t *buffer, size_t count, uintmax_t
*readcount = i; *readcount = i;
cleanup: cleanup:
if (dirbuffer) free(dirbuffer);
vmm_unmap(dirbuffer, INODE_SIZE(&node->inode) + 1, 0);
return err; return err;
} }